JP5337968B2 - Optical element manufacturing method and optical element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing an optical element that irradiates the inside of an optical polymer structure with femtosecond laser light and heating the structure to make the refractive index difference between a laser irradiation portion and a non-irradiation portion large, and to provide an optical element having high diffraction efficiency and an optical element having an optical waveguide with small propagation loss. <P>SOLUTION: The method of manufacturing the optical element includes a laser irradiation stage of irradiating the inside of the optical polymer structure with the femtosecond laser light of 10<SP>-15</SP>to 10<SP>-11</SP>second in pulse width to vary the refractive index of the irradiation portion; and a heating process of heating the optical polymer structure. In the heating stage, the heating is carried out under a condition of 0.8&le;T/T<SB>g</SB>&le;1.13, where T is the absolute temperature of heating temperature and T<SB>g</SB>is the absolute temperature of the glass transition point of a material constituting the optical polymer structure. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

The present invention irradiates an optical polymer structure with an ultrashort pulse laser (hereinafter also referred to as “femtosecond laser”) having a pulse width of 10 ⁻¹⁵ seconds to 10 ⁻¹¹ seconds, and the refractive index of the laser irradiation portion. The present invention relates to a method for manufacturing an optical element and an optical element.

  In recent years, apart from a method of manufacturing an optical element by a process such as lithography, a femtosecond laser is irradiated on the inside of a glass or optical polymer structure, and the refractive index of the irradiated part is changed, for example, a diffractive optical element or optical A method for manufacturing an optical element having a waveguide is known. In this method, the laser to be irradiated is condensed by a lens or the like, and the focal position is moved inside the optical polymer structure, so that the structural change portion in which the refractive index has changed is changed inside the optical polymer structure. It can be formed in any part. (See Patent Document 1). The size, shape, and degree of structural change of the laser irradiation part with different refractive index, etc. are the laser irradiation time, the moving direction and speed of the focal position of the laser, the material of the optical polymer structure, the pulse width of the laser It can be adjusted by the irradiation energy or the numerical aperture of the lens. A femtosecond laser is obtained using a titanium / sapphire crystal as the laser medium, and even with the same output, the electric field strength per unit time and unit space is extremely high. Can be induced.

  Changes in the refractive index due to the femtosecond laser are induced by structural changes due to thermal melting and cooling, structural changes due to cross-linking reactions, structural changes due to phase separation, and the like. For example, when the optical polymer material is melted by laser irradiation and cooled, the structure changes from the alignment state before irradiation to the non-alignment state after irradiation. In addition, the structure changes to a crosslinked state after irradiation from an uncrosslinked state before irradiation due to a crosslinking reaction. Alternatively, the structure changes from a mixed or dissolved state to a phase separated state by phase separation. Since the laser irradiation portion having a changed refractive index or the like is directly formed inside, the manufacturing process can be shortened and the elements can be integrated. In addition, when an optical polymer material is used, a structure change portion having a changed refractive index or the like can be formed by a low energy laser of 500 mW or less, and high speed processing is possible.

  Further, a femtosecond laser having a wavelength in the near-infrared region is condensed and irradiated onto a substrate made of quartz glass, and a high refractive region is continuously induced inside the substrate to form an optical waveguide. An optical waveguide manufacturing method is known in which heat treatment is performed for 2 hours or more in a temperature atmosphere of 1000 ° C. (see Patent Document 2). An optical element manufactured by this method has a small propagation loss of the optical waveguide and can suppress the polarization dependence of the propagation loss. Here, the polarization dependence of the propagation loss is the difference between the maximum value and the minimum value of the propagation loss when any polarization is propagated.

By the way, when an optical element is manufactured by a femtosecond laser, it is desired that the induced refractive index change is large. This is because if the difference in refractive index is large, for example, there is a merit that diffraction efficiency is increased in a diffractive optical element. Here, the change in the refractive index refers to the difference between the refractive index induced in the laser irradiated portion and the refractive index of the unirradiated portion. In addition, it is desirable that the induced refractive index change is stable against subsequent temperature changes. This is because the characteristics as an optical element are stabilized under various temperature environments. However, Patent Document 1 discloses a plastic structure as an optical polymer structure, but does not specifically disclose a method for providing a large refractive index difference, and induces a change in refractive index. The stability to subsequent temperature changes is not described. Further, in Patent Document 2, it is stated that the characteristics of an optical waveguide formed in a substrate made of quartz glass are improved by heating by irradiation with a femtosecond laser. The temperature dependence is not described, and the stability of the induced refractive index change against the subsequent temperature change is not described.
JP 2002-249607 A JP 2003-240994 A

  An object of the present invention is to provide a method of manufacturing an optical element that irradiates a femtosecond laser inside an optical polymer structure and increases a refractive index difference between a laser irradiation part and a non-irradiation part by heating. . Another object of the present invention is to provide an optical element having a high diffraction efficiency and an optical waveguide having a small propagation loss.

The method of manufacturing an optical element according to the present invention includes laser irradiation that changes the refractive index of an irradiation part by irradiating the inside of an optical polymer structure with a femtosecond laser having a pulse width of 10 ^-15 seconds to 10 ^-11 seconds. And a heating step for heating, wherein the heating step is 0. When the heating temperature is T in absolute temperature and the absolute temperature of the glass transition point of the material constituting the optical polymer structure is T _g . 8 ≦
It heats on the conditions of T / _Tg <= 1.13.

Heating in the heating step is preferably for 30 seconds or more.
The heating temperature T is within ± 10K of the absolute temperature of the temperature at which the difference in refractive index between the irradiated part and the non-irradiated part becomes the maximum in heating for a predetermined time, and the time when the difference in refractive index is saturated is the shortest. Preferably, the temperature is within ± 10K of the absolute temperature and within ± 10K of the absolute temperature of the temperature at which the difference in refractive index is maximum.

The heating temperature T is an absolute temperature T ₁ that is the maximum temperature to which the optical element is exposed during use.
In the range of 8 ≦ T ₁ / T _g ≦ 1.13, it is preferable to satisfy T ₁ ≦ T.

  The material constituting the optical polymer structure is preferably at least one selected from the group consisting of polymethyl methacrylate, polycarbonate, and cycloolefin polymer.

  The optical polymer structure is made of a mixture containing a base material and an additive, the base material is polymethyl methacrylate, the additive is a diarylethene having a structure represented by the following formula (1), and the base material The mixing ratio of the additive with respect to is preferably 3% by mass or more.

(In the formula (1), R ₁ and R ₄ are an aliphatic hydrocarbon group, a hydroxy group, a nitro group, an amino group or a mercapto group. R ₂ , R ₃ , R ₅ and R ₆ are hydrogen, A substituent selected from the group consisting of an amino group, an aliphatic hydrocarbon group, an aromatic hydrocarbon group, and an aromatic heterocyclic group, or R ₂ and R ₃ , and R ₅ and R ₆ are aromatic carbonized It may constitute hydrogen or an aromatic heterocyclic ring, X and Y are sulfur, nitrogen or oxygen, and ring Z has a structure consisting of alicyclic hydrocarbon, aromatic hydrocarbon or aromatic heterocyclic ring .)
The present invention also relates to an optical element manufactured by the above-described optical element manufacturing method, wherein the difference in refractive index between the irradiated part and the non-irradiated part is 0.0002 or more.

  The stability of the difference in refractive index between the laser irradiated portion and the non-irradiated portion with respect to a temperature change below the heating temperature T is preferably ± 30% or less.

  The irradiating part preferably has a light transmittance of a working wavelength at a thickness of 0.3 mm of the irradiating part of 80% or more.

  According to the manufacturing method of the present invention, it is possible to provide an optical element having a large difference in refractive index between the irradiated part and the non-irradiated part of the femtosecond laser. Therefore, the diffraction efficiency of the diffractive optical element can be increased.

The method for producing an optical element of the present invention includes a step of irradiating an optical polymer structure with a femtosecond laser and a step of heating. In the heating step, the heating temperature is T as an absolute temperature, When the absolute temperature of the glass transition point of the material constituting the molecular structure is T _g , 0.8 ≦
Heating is performed under the condition of T / T _g ≦ 1.13. The refractive index difference between the laser irradiated portion and the non-irradiated portion can be increased by changing the refractive index of the laser irradiated portion inside the optical polymer structure by laser irradiation and then performing heat treatment. As a result, it is possible to provide an optical element in which the difference in refractive index between the laser irradiation part and the non-irradiation part is 0.0002 or more, and the difference in refractive index is preferably 0.0005 or more, more preferably 0.0008 or more. .

  In the present invention, the optical polymer structure means a transparent material in the used wavelength band of an optical element produced from the optical polymer structure, and preferably has a transmittance of 80% or more in the used wavelength band. Further, the shape may be any shape such as a plate shape, a film shape, a specific shape (for example, a lens shape), or a complicated three-dimensional shape.

  In addition, by changing the refractive index of the laser irradiated portion inside the optical polymer structure by laser irradiation, and then performing heat treatment, the difference in refractive index between the laser irradiated portion and the non-irradiated portion is changed to the subsequent temperature. Stabilize against changes. As a result, the stability of the refractive index difference between the laser irradiated portion and the non-irradiated portion with respect to temperature and time change is ± 30% or less, and the stability is preferably ± 20% or less, more preferably ± 15% or less. An element can be provided. Stability refers to the difference between the refractive index obtained from the Bragg primary diffraction efficiency after heat treatment for a predetermined time and the refractive index obtained from the Bragg primary diffraction efficiency after temperature change exposed after the heat treatment. , A value divided by the former refractive index (refractive index obtained from Bragg first-order diffraction efficiency after heat treatment for a predetermined time). When this value is small, it is possible to provide an optical element having good stability over time.

  In addition, it is possible to provide an optical element in which the transmittance of the light having the wavelength used at the laser irradiation portion thickness of 0.3 mm is preferably 80% or more, more preferably 90% or more. Note that the thickness of the laser irradiation part is an optical element with high light utilization efficiency even when the transmittance of the light having the wavelength used at 0.01 mm is 80% or more in consideration of the practical minimum thickness. Available as The light having the wavelength used is visible light, near infrared light, or the like. Therefore, for example, a diffractive optical element having a high diffraction efficiency, an optical waveguide having a small propagation loss, for example, when the radius of curvature is small, and an excellent ability to stabilize the diffraction efficiency and propagation characteristics against temperature changes An optical element can be manufactured.

In the heating step, the refractive index difference between the laser irradiation part and the non-irradiation part is increased, the first-order diffraction efficiency of the optical element is increased, or the refractive index difference between the laser irradiation part and the non-irradiation part against the subsequent temperature change. In terms of improving stability, the value of T / _Tg is set to 0.8 or more, and preferably 0.86 or more. When the heating temperature greatly exceeds T _g , other physical properties of the polymer material change, and therefore T / T _g ≦ 1.13. The heating time varies depending on the value of T / T _{g and} the like, but is generally 30 seconds or longer, preferably 0.5 hours or longer, and more preferably 24 hours or longer. In addition, the heating temperature T is the refraction between the irradiated part and the non-irradiated part in heating for a predetermined time in that the efficiency of expanding the refractive index difference between the laser irradiated part and the non-irradiated part is increased and the heating time is shortened. Within ± 10K of the absolute temperature of the temperature at which the difference in refractive index is maximum, within ± 10K of the absolute temperature of the temperature at which the time for saturation of the difference in refractive index is the shortest, and the time when the difference in refractive index is maximized It is preferably any temperature within ± 10 K of the absolute temperature of the shortest temperature. These temperature conditions are determined by plotting the optical polymer structure to be used under the above heating temperature condition. The predetermined period is not particularly limited, but can be determined by a heating plot of about 168 hours (7 days).

In terms of enhancing the stability against temperature change of the refractive index difference between the laser irradiation portion and the non-irradiated portion, the heating temperature T, when the maximum temperature exposure during use of the optical element and the T _1, T ₁ ≦ T is preferable, and a temperature of (T ₁ +10) ≦ T is more preferable. In particular, when the optical element is used, when exposed to a high temperature T ₂ in a range of 0.8 ≦ T / T _g ≦ 1.13 continuously for a long period of time, T ₂ ≦ T It is preferable to heat for 24 hours or more at a temperature of 120 hours (5 days)
The above is more preferable.

  The heating step may be a general air atmosphere as the atmosphere during heating. For example, in the case of a material that is easily oxidized and deteriorated during heating, such as a cycloolefin polymer, in order to remove oxygen as the atmosphere during heating. The effects of the present invention can also be obtained in a vacuum, a reduced pressure atmosphere, a nitrogen atmosphere, or the like.

  The material constituting the optical polymer structure is a material that is a single polymer or a combination of two or more polymer materials such as a homopolymer, a copolymer, a polymer alloy, and a polymer blend. The polymer is a thermoplastic polymer, a thermosetting polymer, An ultraviolet curable polymer or the like is preferable.

  Thermoplastic polymers include, for example, polymethacrylic acid esters such as polymethyl methacrylate and polyethyl methacrylate, polyacrylic acid esters such as polyethyl acrylate and polybutyl acrylate, copolymers of butyl acrylate and ethyl acrylate, polymethacrylimide, Polystyrene such as polystyrene, ABS resin, AS resin, polyamide such as 6-nylon, 66-nylon, 12-nylon, polyester such as polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, polyethylene, polypropylene Polyolefin such as bisphenol A polycarbonate, polyethersulfone, polynorbornene, siku Olefin polymers, cycloolefin copolymers, polyvinyl chloride, polyvinylidene chloride, polyvinyl acetate, polyvinyl alcohol, polyacetal, polyphenylene ether, polyphenylene sulfide can be preferably used. Further, for example, various thermoplastic elastomers such as acrylic thermoplastic elastomer, styrene thermoplastic elastomer, polyester thermoplastic elastomer, polyolefin thermoplastic elastomer, polyurethane thermoplastic elastomer, and the like can be used.

Thermosetting polymers include thermosetting polyurethane, thermosetting polyester, phenolic resin, melamine resin, epoxy resin, and the like. Fluorine-based resins such as vinylidene fluoride, hexafluoropropylene, and hexafluoroacetone can be used. Moreover, a polysilane polymer is preferable in terms of improving workability. Polysilane polymers include poly (dimethylsilane), poly (methylethylsilane), poly (methylpropylsilane), poly (methylbutylsilane), poly (methylhexylsilane), poly (dihexylsilane), poly (didodecyl) Poly (alkylalkylsilane) such as poly (alkyl silane), poly (alkylcycloalkylsilane) such as poly (methylcyclohexylsilane), poly (alkylarylsilane) such as poly (methylphenylsilane), and poly (diphenylsilane) (Arylarylsilane), polyphenylsilin, polymethylsilin, and other homopolymers having a three-dimensional structure of silicon atoms, poly (dimethylsilane-methylcyclohexylsilane), and poly (dimethylsilane-methylphenylsilane) are used. It can be.

  As a material constituting the optical polymer structure, a mixture containing a base material and an additive can be used. When a mixture containing a base material and an additive is used, the mode in which the base material is polymethyl methacrylate and the additive is a diarylethene having a structure represented by the following formula (1) is not irradiated with the laser irradiation unit. This is preferable in that an optical element having a large difference in refractive index from the portion can be obtained.

(In the formula (1), R ₁ and R ₄ are an aliphatic hydrocarbon group, a hydroxy group, a nitro group, an amino group or a mercapto group. R ₂ , R ₃ , R ₅ and R ₆ are hydrogen, A substituent selected from the group consisting of an amino group, an aliphatic hydrocarbon group, an aromatic hydrocarbon group, and an aromatic heterocyclic group, or R ₂ and R ₃ , and R ₅ and R ₆ are aromatic carbonized It may constitute hydrogen or an aromatic heterocyclic ring, X and Y are sulfur, nitrogen or oxygen, and ring Z has a structure consisting of alicyclic hydrocarbon, aromatic hydrocarbon or aromatic heterocyclic ring .)
In the above formula (1), R ₁ and R ₄ may be the same or different, and are preferably an aliphatic hydrocarbon group, and particularly preferably a methyl group. R _2, R _3, R ₅ and R _6, which may be identical or different from each other, with R _2, R _3, R ₅ and R ₆ constituent atoms of the constituent atoms or aromatic heterocyclic aromatic hydrocarbon In some cases, an embodiment having a t-butyl group or a triphenylamino group is particularly preferable. An embodiment in which X and Y are sulfur atoms is preferred. The ring Z is particularly preferably an embodiment substituted with fluorine.

Of the additives represented by the formula (1), diarylethene having the structure represented by the following formula (2) is preferable in that the difference in refractive index between the laser irradiated portion and the non-irradiated portion can be further enlarged. From the same viewpoint, the mixing ratio of the diarylethene having the structure represented by the formula (1) to the base material is preferably 3% by mass or more, and more preferably 5% by mass or more. On the other hand, the mixing ratio of the additive to the base material is 40% by mass or less in terms of increasing the transmittance of the light of the wavelength used, facilitating laser processing, and increasing the light utilization efficiency of the optical element manufactured by laser processing. Is preferable, and 35 mass% or less is more preferable. Further, the content of the base material and the additive in the optical polymer structure is preferably 80% by mass or more, and more preferably 90% by mass or more, from the viewpoint of increasing the refractive index difference between the laser irradiated part and the non-irradiated part. . When the visible light transmittance of the optical polymer structure is high, the inside of the structure can be visually recognized, the irradiation position and the focal position of the femtosecond laser can be easily adjusted, and laser processing can be facilitated. it can. Moreover, the light utilization efficiency of the optical element manufactured by laser processing can be improved. Therefore, an aspect in which the transmittance of the light having the wavelength used at a thickness of 3 mm when the additive is mixed by 10% by mass is preferably 80% or more, and more preferably 90% or more. The thickness and transmittance of the optical polymer structure are high in light use efficiency even when the transmittance of the light having the wavelength used at 0.1 mm is 80% or more in consideration of the practical thickness. It can be used as an optical element. Note that the thickness of the irradiated portion refers to the length (modified thickness) in the laser entrance direction in which a change in refractive index is induced in the optical polymer structure when the laser is irradiated.

  In the present invention, in the method of irradiating the inside of the optical polymer structure with a femtosecond laser and inducing a refractive index change in the irradiated part, the refractive index induced in the irradiated part is obtained by performing a heat treatment after the laser irradiation. It was newly found that the difference in refractive index between the non-irradiated portion and the non-irradiated portion can be enlarged, and the change in the refractive index difference due to the temperature change thereafter can be stabilized. Although the mechanism by which the difference in refractive index is enlarged and stabilized by heat treatment after laser irradiation is not yet clearly elucidated, the irradiation part is contracted as a structural change, for example, by promoting volume relaxation. It is estimated that the density of increases.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated in detail, this invention is not limited to these.

Example 1
First, 1. 1. Laser irradiation method 2. a method for measuring diffraction characteristics and a method for calculating a difference in refractive index; A method for measuring the transmittance of the refractive index changing portion by laser irradiation will be described.

1. Laser irradiation method The femtosecond laser had a center wavelength of 800 nm, a pulse width of 118 × 10 ⁻¹⁵ seconds, and a repetition frequency of 1 kHz. N. A. An objective lens having a numerical aperture of 0.13 (5 times magnification) was used, and an aperture having a diameter of 5.5 mm was set in front of the objective lens. Further, when the refractive index of each material is n, the inside of the optical polymer structure is condensed and irradiated so that the movement from the surface of the structure to the inside becomes 500 μm / n, and the period Λ is 10 μm. A diffraction grating having a side of 1 mm was prepared. The stage speed was scanned at 1 mm / s.

2. Method for Measuring Diffraction Characteristics and Calculation Method for Refractive Index Difference Δn Induced by Femtosecond Laser Irradiation As diffraction characteristics, diffraction efficiency and diffraction angle were measured. That is, the measurement was performed by tilting a diffraction grating formed by a femtosecond laser with a period Λ of 10 μm and a side of 1 mm from a direction perpendicular to the diffraction grating by a Bragg angle θ _B. The laser used for measurement is a He—Ne laser (wavelength λ =
632.8 nm) and incident with a beam diameter of φ0.5 mm. Then from the diffraction grating 500
A screen was placed at a position of mm, and the diffraction angle was calculated from the interval between the 0th order light and the 1st order light.

In the case of the present embodiment, θ _B = 1.8 ° because of the relationship 2Λsin θ _B = λ, so the angle at which the diffraction grating is tilted is 1.8 °, and the 0th order light and the 1st order light at positions 500 mm apart. Since the distance is about 31.7 mm, diffracted light with a period Λ = 10 μm was confirmed. On the other hand, the refractive index difference Δn between the irradiated part and the non-irradiated part by the femtosecond laser was derived from the diffraction efficiency. That is, the measured first-order diffraction efficiency is η ₁ , the refractive index difference is Δn, and the length of the refractive index changing portion is L
The refractive index difference Δn was determined from the following equation (3), where λ is the wavelength at the time of measurement and θ _B is the Bragg diffraction angle.

  The modified thickness L was measured by observing with a transmission microscope. Here, the reason why Δn is derived from the diffraction efficiency is that in this embodiment, the parameter Q value representing the thickness is a value close to 10, which is a so-called “thick” diffraction grating. This is because there is almost no absorption at 90% or more. The Q value is expressed as the following equation (4).

3. Method for Measuring Transmittance of Refractive Index Change Part by Laser Irradiation After transmitting through a diffraction grating having a thickness of 160 μm to 400 μm with respect to the amount of light after passing through the optical polymer structure by visible light having a wavelength of 632.8 nm The ratio of the amount of light obtained by adding all the orders of light that were diffracted and branched.

In this example, polymethyl methacrylate (hereinafter referred to as “PMMA”) having a refractive index of 1.490 and a glass transition point of 120 ° C. was used as a material constituting the optical polymer structure. Moreover, PMMA (trade name acrylite, model # 000) manufactured by Mitsubishi Rayon Co., Ltd. was used as PMMA. Next, the inside of the optical polymer structure was irradiated with a femtosecond laser so that the laser pulse energy on the processed surface was 1000 nJ. As a result, the modified thickness L is 370 μm, the Q value is 9.9 according to the equation (4), and the first-order diffraction efficiency at the Bragg angle is 1.9.
%Met. The refractive index difference Δn between the laser irradiated portion and the non-irradiated portion was 1.5 × 10 ⁻⁴ , and the light transmittance at a wavelength of 632.8 nm of the laser irradiated portion was 90.5%. Then, after carrying out the daily treatment in each temperature atmosphere of 25 ° C. (room temperature), 40 ° C., 50 ° C., 60 ° C., 70 ° C., 80 ° C., 90 ° C. and 100 ° C., at 25 ° C. (room temperature) The diffraction efficiency was measured. Table 1 and FIG. 1 show changes over time in the first-order diffraction efficiency at the Bragg angle after the daily treatment in each temperature atmosphere. In addition, Table 1 shows the light transmittance at a wavelength of 632.8 nm after the elapse of 7 days from the laser irradiation part. Among the temperature conditions, the atmosphere of 40 ° C. to 100 ° C. was adjusted by a constant temperature heating tank.

As is apparent from the results of Table 1 and FIG. 1, at 25 ° C., the first-order diffraction efficiency at the Bragg angle is 1.1% after 7 days from laser irradiation, while it is 2.7% or more at 40 ° C. or higher and 2%. Improve by more than 5 times. In particular, in the temperature atmosphere of 60 ° C. or higher, the first-order diffraction efficiency was significantly increased as compared with that before the heat treatment. Since the absolute temperature T _g of the glass transition point of PMMA is 120 + 273 = 393K, and the absolute temperature T when heated at 40 ° C. is 40 + 273 = 313K, T / T _g
Becomes 0.8. Moreover, since the absolute temperature T when heated at 60 ° C. is 60 + 273 = 333 K, T / T _g is 0.85. Accordingly, the diffraction efficiency is increased by heating in an atmosphere having a T / T _g of 0.8 or more, and in particular, the diffraction efficiency is dramatically improved by heating in an atmosphere having a T / T _g of 0.85 or more. It turned out to increase.

  Furthermore, when heated at 80 ° C., the first-order diffraction efficiency at the Bragg angle reached 70% after 5 days, as shown in FIG. Therefore, the diffraction efficiency of 70% when treated at 80 ° C. for 5 days is about 64 times the diffraction efficiency of 1.1% at 25 ° C., and the saturation value (70%) of the diffraction efficiency is the number of days elapsed. However, in 7 days or less, it was found to be higher than the saturation value of other temperature conditions. In addition, in the case of 70 ° C., the saturation value (70%) was reached after 20 days or more, so the number of days until saturation is reached is the shortest in the 80 ° C. condition and the most efficient. I understood that it can be processed. That is, under the conditions of this example, the diffraction efficiency was saturated at the highest value under the temperature condition of 70 ° C. to 80 ° C., and 80 ° C. was the peak temperature in that the processing time for that was short. .

Table 1 shows the light transmittance at a wavelength of 632.8 nm of the laser-irradiated part after a lapse of 7 days in a predetermined atmosphere. From the results shown in Table 1, the light transmittance at a wavelength of 632.8 nm was 90% or more for all the samples regardless of before and after heating. In all the samples, the modified thickness L was 370 μm and remained unchanged before and after the heat treatment. That is, the transparency and the modification length L of the modified part before and after heating were unchanged, and the measurement conditions were also unchanged. However, the refractive index difference Δn between the laser irradiation part and the non-irradiation part is, for example, Δn is 1.1 × 10 ⁻⁴ in an atmosphere at 25 ° C. where the diffraction efficiency is 1.1%. In an atmosphere at 80 ° C. where the diffraction efficiency is 70%, Δn is 10.8 × 10 ^−4, which is about 10 times larger. Therefore, it was considered from equation (3) that the increase in diffraction efficiency was due to an increase in the refractive index difference Δn.

  Further, under the same femtosecond laser conditions as in Example 1, the optical height was obtained by performing a heat treatment at 150 ° C. for 30 seconds after irradiating the femtosecond laser so that the laser pulse energy on the processed surface was 500 nJ. A molecular structure and an optical polymer structure subjected to a heat treatment at 170 ° C. for 30 seconds were prepared, and diffraction efficiency and the like were evaluated in the same manner as described above. As a result, when the heat treatment was performed at 150 ° C. for 30 seconds, the Bragg first-order diffraction efficiency was 2.5 times that of the case where the heat treatment was not performed. When the heat treatment was performed at 170 ° C. for 30 seconds, the Bragg first-order diffraction efficiency was 1.8 times that of the case where the heat treatment was not performed. At this time, the modified thickness L did not change at 285 μm, the light transmittance at a wavelength of 632.8 nm did not change at 90% or more, and the measurement conditions were unchanged. Therefore, it was considered from equation (3) that the increase in diffraction efficiency was due to an increase in the refractive index difference Δn.

Accordingly, the same effect of the present invention that the refractive index difference Δn is increased even under the condition of T / T _g = (170 + 273) / (120 + 273) = 1.13 where the heating temperature after laser irradiation is equal to or higher than the glass transition point. I understood that it was played.

(Example 2)
In this example, a polycarbonate (hereinafter referred to as “PC”) having a refractive index of 1.585 and a glass transition point of 142 ° C. was used as a material constituting the optical polymer structure. In addition, a PC manufactured by Teijin Ltd. (trade name Panlite, model AD-5503) is used as the PC, and a femtosecond laser is formed inside the optical polymer structure so that the laser pulse energy on the processed surface is 500 nJ. Was irradiated. As a result, the modified thickness L was 330 μm, the Q value was 8.3 according to Equation (4), and the first-order diffraction efficiency at the Bragg angle was 0.3%. The refractive index difference Δn between the laser irradiated portion and the non-irradiated portion was 0.7 × 10 ⁻⁴ , and the light transmittance at a wavelength of 632.8 nm of the laser irradiated portion was 95.8%. Then, after performing daily treatment in each temperature atmosphere of 25 ° C. (room temperature), 70 ° C., 90 ° C., 110 ° C., 120 ° C., 130 ° C. and 150 ° C., the next time at 25 ° C. (room temperature) Changes in folding efficiency over time were measured. Table 2 and FIG. 2 show changes over time in the first-order diffraction efficiency at the Bragg angle after the daily treatment in each temperature atmosphere. Table 2 shows the light transmittance at a wavelength of 632.8 nm in the laser irradiation part after 7 days. Among each temperature condition, the atmosphere of 70 ° C. to 150 ° C. was adjusted by a constant temperature heating tank.

As is apparent from the results of Table 2 and FIG. 2, it was found that the first-order diffraction efficiency at the Bragg angle increases with the passage of days in an atmosphere of 70 ° C. or higher with respect to an atmosphere of 25 ° C. The absolute temperature T _g of the glass transition point of PC is 142 + 273 = 415K, and the absolute temperature T when heated at 70 ° C. is 70 + 273 = 343K, so T / T _g is 0.83. Therefore, it was found that the diffraction efficiency is increased by heating in an atmosphere having a T / T _g of 0.83 or more.

  In particular, when heated at 120 ° C., the first-order diffraction efficiency at the Bragg angle reached 18% after 5 days, as shown in FIG. Therefore, the diffraction efficiency of 18% after 5 days at 120 ° C is about 4.5 times the diffraction efficiency of 4% after 7 days at 25 ° C, and the saturation value (18%) of the diffraction efficiency is others. In view of the fact that it is higher than the saturation value of the temperature conditions, it was found that the conditions were such that the treatment could be performed with the highest efficiency. That is, under the conditions of this example, 120 ° C. was the peak temperature.

Table 2 shows the light transmittance at a wavelength of 632.8 nm of the laser-irradiated part after a lapse of 7 days under a predetermined atmosphere. From the results in Table 2, the light transmittance at a wavelength of 632.8 nm was 90% or more for any sample, regardless of whether it was heated or not. Further, in any sample, as in Example 1, the transparency of the modified portion and the modified length L before and after heating were unchanged, and the measurement conditions were also unchanged. However, the refractive index difference Δn between the laser irradiation part and the non-irradiation part is, for example, Δn is 2.4 × 10 ⁻⁴ in an atmosphere at 25 ° C. where the diffraction efficiency is 4%, whereas the diffraction efficiency is low. In an atmosphere at 120 ° C. where 18% is 18%, Δn is 5.4 × 10 ^−4, which is about 2.3 times larger. Therefore, it was considered that the increase in diffraction efficiency was due to an increase in the refractive index difference Δn.

In addition, it was found from this example that the diffraction efficiency and Δn are increased even at 150 ° C., which is higher than the glass transition point 142 ° C. That is, the refractive index difference induced in the optical polymer structure does not disappear even when the glass transition point is exceeded, and the refractive index difference can be enlarged. In addition, even if it exceeds the glass transition point, in the case of a temperature near the glass transition point at which deformation such as deflection does not cause a problem, the glass transition point may be exceeded.

(Example 3)
In this example, a cycloolefin polymer (hereinafter referred to as “COP”) having a refractive index of 1.509 and a glass transition point of 123 ° C. was used as a material constituting the optical polymer structure. Also, COP (trade name ZEONEX, model 330R) manufactured by Nippon Zeon Co., Ltd. is used as the COP, and the inside of the optical polymer structure is irradiated with a femtosecond laser so that the laser pulse energy on the processed surface becomes 400 nJ. did. N. A. (Numerical aperture) 0.25 objective lens (magnification 10 times) is used, an aperture with a diameter of 5.5 mm is set in front of the objective lens, and the movement from the surface of the structure to the inside is 1000 μm / n Thus, the inside of the optical polymer structure was condensed and irradiated. The other conditions were the same as in Example 1.

As a result, the modified thickness L was 160 μm, the Q value was 4.2 according to Equation (4), and the first-order diffraction efficiency at the Bragg angle was 0.1%. The refractive index difference Δn between the laser irradiated part and the non-irradiated part was 0.7 × 10 ⁻⁴ , and the light transmittance at a wavelength of 632.8 nm of the laser irradiated part was 99%. Then, after performing a time-dependent process in each temperature atmosphere of 25 degreeC (room temperature), 50 degreeC, 70 degreeC, 90 degreeC, and 100 degreeC, diffraction efficiency was measured under 25 degreeC (room temperature). Table 3 and FIG. 3 show the first-order diffraction efficiency at the Bragg angle after the aging treatment in each temperature atmosphere. Table 3 shows the light transmittance at a wavelength of 632.8 nm in the laser irradiation part after 7 days. Among the temperature conditions, the atmosphere of 50 ° C. to 100 ° C. was adjusted by a constant temperature heating tank.

As is apparent from the results of Table 3 and FIG. 3, it was found that the first-order diffraction efficiency at the Bragg angle increases in an atmosphere of 50 ° C. or higher with respect to an atmosphere of 25 ° C. The absolute temperature T _g of the glass transition point of COP is 123 + 273 = 396 K, and the absolute temperature T when heated at 50 ° C.
Since 50 + 273 = 323K, T / T _g is 0.82. Therefore, T /
By T _g is heated at 0.82 above atmosphere, it was found that the diffraction efficiency is increased.

  In particular, when heated at 100 ° C., as shown in Table 3 and FIG. 3, the first-order diffraction efficiency at the Bragg angle tended to maximize to about 14% after 0.5 to 2 hours. Therefore, the diffraction efficiency of 14% after 0.5 hours at 100 ° C. is about twice the diffraction efficiency of 6.6% after 7 days at 25 ° C., and 0.5 hours after other temperature conditions. Since it was higher than the diffraction efficiency at the time, it was found that the conditions were such that the diffraction efficiency could be increased in a short time. That is, under the conditions of this example, 100 ° C. was the peak temperature.

Table 3 shows the light transmittance at a wavelength of 632.8 nm of the laser-irradiated part after a lapse of 7 days in a predetermined atmosphere. From the results shown in Table 3, the light transmittance at a wavelength of 632.8 nm was 90% or more for any sample regardless of before and after heating. Further, in any sample, as in Example 1, the transparency of the modified portion and the modified length L before and after heating were unchanged, and the measurement conditions were also unchanged. However, the refractive index difference Δn between the laser irradiated portion and the non-irradiated portion is, for example, Δn is 6.5 × 10 ⁻⁴ in an atmosphere at 25 ° C. where the diffraction efficiency is 6.6%. In an atmosphere at 70 ° C. with a diffraction efficiency of 13.5%, Δn was 9.5 × 10 ⁻⁴ , which was about 1.5 times larger. Therefore, it was considered that the increase in diffraction efficiency was due to an increase in the refractive index difference Δn.

  In this example, a general air atmosphere is used as the atmosphere during heating. However, in the case of a material that is easily oxidized and deteriorated during heating depending on the grade such as a cycloolefin polymer, oxygen is removed as the atmosphere during heating. In addition, the same effects can be obtained as a vacuum, a reduced pressure atmosphere, a nitrogen atmosphere, or the like.

Example 4
In this example, a mixture of a base material and an additive was used as the material constituting the optical polymer structure. As the base material, PMMA having a refractive index of 1.49 and a glass transition point of 95 ° C. was used. As a method for producing PMMA, 30 g of methyl methacrylate (hereinafter referred to as “MMA”) and an initiator of 0.1 mol% with respect to MMA were added. Heating was performed at 55 ° C. for 72 hours in a nitrogen atmosphere to obtain bulk PMMA. In this case, the glass transition point is 95 ° C. Further, as the additive, diarylethene having a refractive index of 1.56 having a structure represented by the following formula (2) was used, and 10% by mass of diarylethene was mixed with the base material. As a preparation method, 10% by mass of diarylethene was dissolved in 30 g of MMA, and 0.1 mol% of an initiator was added to MMA. This was heated at 55 ° C. for 72 hours under a nitrogen atmosphere to obtain PMMA containing bulk diarylethene. The glass transition point of this mixture was 85 ° C. Next, a femtosecond laser was irradiated into the optical polymer structure so that the laser pulse energy on the processed surface was 1100 nJ. As a result, the modified thickness L was 430 μm, the Q value was 11.5 according to the equation (4), and the first-order diffraction efficiency at the Bragg angle was 9.3%. The refractive index difference Δn between the laser irradiated part and the non-irradiated part was 2.8 × 10 ⁻⁴ , and the light transmittance at a wavelength of 632.8 nm of the laser irradiated part was 60%.

  Then, after processing for 7 days in each atmosphere at 25 ° C. (room temperature) and 70 ° C., the first-order diffraction efficiency was measured at 25 ° C. (room temperature). FIG. 4 shows the first-order diffraction efficiency at the Bragg angle after 7 days in each temperature atmosphere and the light transmittance at a wavelength of 632.8 nm of the laser irradiation part. The atmosphere at 70 ° C. was adjusted with a constant temperature heating tank.

As is apparent from the results of FIG. 4, the first-order diffraction efficiency was improved 7 times or more to 89.6% in an atmosphere at 70 ° C. or higher, compared to 12.1% in an atmosphere at 25 ° C. Further, the light transmittance at a wavelength of 632.8 nm of the grating portion was improved from 80% to 92% by the heat treatment. The absolute temperature T _g of the glass transition point of the optical polymer material is 80 + 273 = 353 K, and 70 ° C.
Since the absolute temperature T when heated at 70 is 70 + 273 = 343K, T / T _g is 0.9.
7 Therefore, it was confirmed that heating in an atmosphere having a T / T _g of 0.97 increases the diffraction efficiency even in an embodiment in which the optical polymer structure is composed of a mixture.

In all samples, the modified thickness L was 430 μm and did not change before and after the heat treatment. Moreover, although the transparency of the modified portion changes before and after heating, it can be said that this change is in the direction opposite to the increase in refractive index due to isomerization of diarylethene because this change is in the direction of improving the transparency. The measurement conditions were also the same, but the refractive index difference Δn between the laser irradiation part and the non-irradiation part was Δn of 3.4 × 10 ^{−4 in} an atmosphere at 25 ° C. where the diffraction efficiency was 12.1%. On the other hand, in an atmosphere at 70 ° C. where the diffraction efficiency is 89.6%, Δn was 11.6 × 10 ⁻⁴ , which was 3.4 times larger. Therefore, the increase in diffraction efficiency was considered to be due to the increase in the refractive index difference Δn, as in Examples 1-3.

(Example 5)
In this example, the same conditions as in Example 1 were used except that the center wavelength of the femtosecond laser was 400 nm, and the laser pulse energy on the processed surface was 164 nJ inside the optical polymer structure. Femtosecond laser was irradiated. As a result, the modified thickness L is 240 μm, the Q value obtained by the equation (4) is 6.4, and the first-order diffraction efficiency at the Bragg angle is 1.
0%. The refractive index difference Δn between the laser irradiated part and the non-irradiated part was 1.7 × 10 ⁻⁴ , and the light transmittance at a wavelength of 632.8 nm of the laser irradiated part was 98%. Then, after carrying out heat treatment in each temperature atmosphere at 25 ° C. (room temperature), 50 ° C., 70 ° C., and 100 ° C., the diffraction efficiency was measured at 25 ° C. (room temperature). Table 4 and FIG. 5 show the first-order diffraction efficiency at the Bragg angle after the daily heat treatment in each temperature atmosphere. In addition, Table 4 shows the light transmittance at a wavelength of 632.8 nm after 8 days from the laser irradiation portion.

  Among the temperature conditions, the atmosphere of 50 ° C. to 100 ° C. was adjusted by a constant temperature heating tank.

As is apparent from the results of Table 4 and FIG. 5, the first-order diffraction efficiency at the Bragg angle is improved at 50 ° C. or higher, and particularly in the temperature atmosphere at 50 ° C. and 70 ° C., the first-order diffraction efficiency is higher than before heat treatment. Increased significantly. The absolute temperature T _g of the glass transition point of PMMA is 120 + 273 = 393K, and the absolute temperature T when heated at 50 ° C. is 50 + 273 = 323 K, so T / T _g is 0.85. Therefore, it was found that the diffraction efficiency is increased by heating in an atmosphere having a T / T _g of 0.85 or more.

Furthermore, when heated at 70 ° C., as shown in FIG. 5, the first-order diffraction efficiency at the Bragg angle reached 27% after 5 days and 30% after 18 days. Therefore, the diffraction efficiency of 30.1% when treated at 70 ° C. for 18 days is zero when the diffraction efficiency is treated for 8 days at 25 ° C.
. It was about 43 times that of 7%, and was found to be higher than the diffraction efficiency value at which saturation was achieved and the maximum diffraction efficiency value at other temperature conditions. That is, under the conditions of this example, the diffraction efficiency was saturated at the highest value in the case of the temperature condition of 70 ° C., and 70 ° C. was the peak temperature in that the processing time for that was short.

Table 4 shows the visible light transmittance of the laser-irradiated part after 8 days in a predetermined atmosphere. From the results shown in Table 4, the visible light transmittance of each sample was 90% or more regardless of before and after heating. In all the samples, the modified thickness L was 240 μm and remained unchanged before and after the heat treatment. That is, the transparency and the modification length L of the modified part before and after heating were unchanged, and the measurement conditions were also unchanged. However, the refractive index difference Δn between the laser irradiated portion and the non-irradiated portion is, for example, Δn is 1.9 × 10 ⁻⁴ in an atmosphere at 25 ° C. where the diffraction efficiency is 1.2%. In an atmosphere at 70 ° C. with a diffraction efficiency of 31.6%, Δn was 10.0 × 10 ⁻⁴ , which was about 5.3 times larger. Therefore, it was considered from equation (3) that the increase in diffraction efficiency was due to an increase in the refractive index difference Δn.

  In the following Examples 6 to 9, after the femtosecond laser irradiation, the heat treatment was performed, and then the temperature atmosphere conditions were changed to evaluate the diffraction efficiency.

(Example 6)
In this example, first, a femtosecond laser was irradiated into the optical polymer structure so that the laser pulse energy on the processed surface was 500 nJ. Further, the inside of the optical polymer structure was condensed and irradiated so that the movement from the surface of the structure to the inside was 1000 μm / n. The other conditions were the same as in Example 1. As a result, the modified thickness L was 315 μm, the Q value was 8.4 according to Equation (4), and the first-order diffraction efficiency at the Bragg angle was 1.3%. The refractive index difference Δn between the laser irradiated part and the non-irradiated part was 1.5 × 10 ⁻⁴ , and the light transmittance at a wavelength of 632.8 nm of the laser irradiated part was 97%.

Thereafter, a lapse process was performed for 7 days in each temperature atmosphere of 25 ° C. (room temperature), 70 ° C., and 100 ° C. The atmosphere at 70 ° C. and 100 ° C. was adjusted by a constant temperature heating tank. When the measurement was performed at 25 ° C. (room temperature) after the treatment, the first-order diffraction efficiency at the Bragg angle after 7 days of treatment at 25 ° C. (room temperature) was 0.9%. The refractive index difference Δn is 1.2 × 10 ⁻⁴ , the light transmittance at a wavelength of 632.8 nm of the laser irradiation part is 97%, and 1 at the Bragg angle after 7 days of processing at 70 ° C. The next diffraction efficiency is 60.5%, the refractive index difference Δn between the laser irradiated part and the non-irradiated part is 11.4 × 10 ⁻⁴ , and the light transmittance at the wavelength of 632.8 nm of the laser irradiated part is 99%. The first-order diffraction efficiency at the Bragg angle after 7 days of processing at 100 ° C. is 7.1%, the refractive index difference Δn between the laser irradiated part and the non-irradiated part is 3.4 × 10 ⁻⁴ , and laser irradiation. The light transmittance at a wavelength of 632.8 nm was 97%.

  After that, each of the optical polymer structures subjected to the above-described treatment was subjected to 113 hours in a temperature atmosphere of −25 ° C., 25 ° C. (room temperature), 70 ° C., and 100 ° C. in a temperature cycle atmosphere of H / C1. The treatment was performed under conditions of 110 cycles and 102 cycles in an H / C2 temperature cycle atmosphere, and then the measurement was performed at 25 ° C. (room temperature). Here, H / C1 is a temperature cycle in which a cycle of 30 minutes in a temperature atmosphere of −25 ° C. and 30 minutes in a temperature atmosphere of −70 ° C. is defined as one cycle. Indicates a temperature cycle in which 30 minutes pass under a temperature atmosphere of −40 ° C. and 30 minutes pass under a temperature atmosphere of 100 ° C. as one cycle.

Tables 5 and 6 show that after the laser irradiation, the first-order diffraction efficiency and the laser irradiation part after being exposed to the atmospheric conditions after each lapse of 7 days at temperatures of 25 ° C. (room temperature), 70 ° C., and 100 ° C. The light transmittance at a wavelength of 632.8 nm is shown. Further, FIG. 6 shows that after laser irradiation, 7 ° C. at 25 ° C. (room temperature).
The graph of the 1st-order diffraction efficiency after exposing to each temperature atmospheric condition after progressing a day is shown. Further, FIG. 7 shows a graph of first-order diffraction efficiency after exposure to each temperature and atmosphere condition after 7 days at 70 ° C. after laser irradiation. Further, FIG. 8 shows a graph of the first-order diffraction efficiency after exposure to each temperature and atmosphere condition after 7 days at 100 ° C. after laser irradiation. Among each temperature atmosphere condition, −25 ° C. was adjusted by a constant temperature cooling bath, 70 ° C. and 100 ° C. by a constant temperature heating bath, and H / C1 and H / C2 were adjusted by a heat cycle test bath.

As is apparent from Table 5 and FIG. 6, those treated for 7 days at 25 ° C. (room temperature) are those after 113 hours of each temperature atmosphere, 110 cycles of H / C1, and 102 cycles of H / C2. Later, at −25 ° C. and 25 ° C. (room temperature), the maximum stability is obtained, and the first-order diffraction efficiency at the Bragg angle is about −54% (the stability of the refractive index difference Δn is about −32%). , 70 ° C., 100 ° C., H / C1, and H / C2, the diffraction efficiency changes greatly, and the maximum stability is + 5300% as the first-order diffraction efficiency at the Bragg angle (+ 700% as the stability of the refractive index difference Δn) ) Here, the stability is defined as a value of the diffraction efficiency after each temperature atmosphere passage treatment is α, a value of the diffraction efficiency before each temperature atmosphere passage treatment is β,
(Α−β) / β × 100% Formula (5)
The diffraction efficiency before each temperature atmosphere progress treatment and the rate of change with respect to Δn are shown, and the sign of ± indicates increase or decrease.

  Further, as is apparent from Table 5 and FIG. 7, those treated at 70 ° C. for 7 days were obtained after 113 hours of each temperature atmosphere, after 110 cycles of H / C1, and after 102 cycles of H / C2. , −25 ° C., 25 ° C. (room temperature), 70 ° C., and H / C1, the change in diffraction efficiency is small, and the maximum stability is + 13% as the first-order diffraction efficiency at the Bragg angle (stable refractive index difference Δn) However, the diffraction efficiency greatly changes at 100 ° C. and H / C2, and the maximum stability is −95% as the first-order diffraction efficiency at the Bragg angle (the stability of the refractive index difference Δn). -80%).

In addition, as is apparent from Table 5 and FIG. 8, the sample treated at 100 ° C. for 7 days was after 113 hours of each temperature atmosphere, 110 cycles of H / C1, and 102 cycles of H / C2. , −25 ° C., 25 ° C. (room temperature), 70 ° C., 100 ° C., H / C 1, H / C 2, the change in diffraction efficiency is small, and the first-order diffraction at the Bragg angle even with maximum stability The efficiency is about + 23% (the stability of the refractive index difference Δn is about + 11%).

  In any of these cases, the modified length L does not change, and the light transmittance at a wavelength of 632.8 nm of the laser irradiation portion hardly changes at 90% or more as shown in Table 6. The change in the diffraction efficiency after the temperature atmosphere process was considered as the change in the refractive index difference Δn.

Therefore, when heat treatment is performed after laser irradiation, the first-order diffraction efficiency and the refractive index difference Δn at the Bragg angle are stabilized if the subsequent temperature and temperature change are equal to or lower than the heat treatment temperature. However, when the temperature variation including the heat treatment temperature is higher or higher, the diffraction tendency depends on the temperature tendency during the heat treatment of Example 1, that is, the diffraction efficiency increases at 40 ° C. or higher and maximizes at 70-80 ° C. It can be seen that the diffraction efficiency and Δn are greatly changed to show the efficiency change. That is, in order to stabilize the refractive index difference Δn with respect to the subsequent temperature change of the optical element manufactured by the method of inducing the refractive index change inside the optical polymer structure by femtosecond laser irradiation, use of the optical element is required. When the absolute temperature display T _{1 of the} highest temperature that is sometimes exposed is included in 0.8 ≦ T ₁ / T _g ≦ 1.13, heating is performed at a temperature T ₁ ≦ T as the heating temperature T after the femtosecond laser irradiation. It turns out that processing is good.

(Example 7)
In this example, first, a femtosecond laser was irradiated into the optical polymer structure so that the laser pulse energy on the processed surface was 400 nJ. N. A. An objective lens having a numerical aperture of 0.25 (magnification of 10) was used, an aperture having a diameter of 5.5 mm was set in front of the objective lens, and the inside of the optical polymer structure was condensed and irradiated. The other conditions were the same as in Example 2. As a result, the modified thickness L was 190 μm, the Q value was 4.8 according to Equation (4), and the first-order diffraction efficiency at the Bragg angle was 0.3%. Further, the refractive index difference Δn between the laser irradiated portion and the non-irradiated portion was 1.1 × 10 ⁻⁴ , and the light transmittance at a wavelength of 632.8 nm of the laser irradiated portion was 98%.

Thereafter, a lapse treatment was performed for 10 days in each temperature atmosphere of 25 ° C. (room temperature), 70 ° C., and 130 ° C. The atmosphere at 70 ° C. and 130 ° C. was adjusted by a constant temperature heating tank. When the measurement is performed at 25 ° C. (room temperature) after the treatment, the first-order diffraction efficiency at the Bragg angle after the treatment for 10 days at 25 ° C. (room temperature) is 2.6%. The refractive index difference Δn is 3.4 × 10 ⁻⁴ , the light transmittance at a wavelength of 632.8 nm of the laser irradiation part is 97%, and 1 at the Bragg angle after 10 days of processing at 70 ° C. The next diffraction efficiency is 9.3%, the refractive index difference Δn between the laser irradiated part and the non-irradiated part is 6.6 × 10 ⁻⁴ , and the light transmittance at the wavelength of 632.8 nm of the laser irradiated part is 96%. Also, the first-order diffraction efficiency at the Bragg angle after 10 days of processing at 130 ° C. is 23.1%, the refractive index difference Δn between the laser irradiation part and the non-irradiation part is 10.6 × 10 ⁻⁴ , and laser irradiation. The light transmittance of the part at a wavelength of 632.8 nm was 98%.

Further, after that, each of the optical polymer structures subjected to the above treatment was subjected to 190 hours in each temperature atmosphere at −25 ° C., 25 ° C. (room temperature), 70 ° C., and 100 ° C. After the progress treatment was performed under the conditions of 183 cycles and 175 cycles in an H / C2 temperature cycle atmosphere, the measurement was performed at 25 ° C. (room temperature). Tables 7 and 8 show that the first-order diffraction efficiency and the laser irradiation part after exposure to each atmospheric condition after 10 days at 25 ° C. (room temperature), 70 ° C., and 130 ° C. after laser irradiation. The light transmittance at a wavelength of 632.8 nm is shown. FIG. 9 shows a graph of the first-order diffraction efficiency after exposure to each temperature and atmosphere condition after 10 days at 25 ° C. (room temperature) after laser irradiation. Further, FIG. 10 shows a graph of the first-order diffraction efficiency after exposure to each temperature and atmosphere condition after 10 days at 70 ° C. after laser irradiation. Further, FIG. 11 shows a graph of the first-order diffraction efficiency after exposure to each temperature and atmosphere condition after 10 days at 130 ° C. after laser irradiation. Among each temperature atmosphere condition, −25 ° C. was adjusted by a constant temperature cooling bath, 70 ° C. and 100 ° C. by a constant temperature heating bath, and H / C1 and H / C2 were adjusted by a heat cycle test bath.

  As is apparent from Table 7 and FIG. 9, the sample treated at 25 ° C. (room temperature) for 10 days was after 190 hours of each temperature atmosphere, 183 cycles of H / C1, and 175 cycles of H / C2. Later, at −25 ° C. and 25 ° C. (room temperature), the maximum stability and the first-order diffraction efficiency at the Bragg angle is about + 35% (+ 16% as the stability of the refractive index difference Δn), but 70 ° C. At 100 ° C., H / C1, H / C2, the diffraction efficiency changes greatly, and the maximum stability is about + 660% as the first-order diffraction efficiency at the Bragg angle (+ 185% as the stability of the refractive index difference Δn). Become.

  In addition, as is apparent from Table 7 and FIG. 10, the samples treated at 70 ° C. for 10 days were observed after 190 hours of each temperature atmosphere, after 183 cycles of H / C1, and after 175 cycles of H / C2. , −25 ° C., 25 ° C. (room temperature), 70 ° C., and H / C1, the change in diffraction efficiency is small, and even with the maximum stability, the first-order diffraction efficiency at the Bragg angle is + 25% (stable refractive index difference Δn) However, the diffraction efficiency greatly changes at 100 ° C. and H / C2, and the maximum stability, the first-order diffraction efficiency at the Bragg angle is + 100% (the stability of the refractive index difference Δn). + 44%).

  In addition, as is apparent from Table 7 and FIG. 11, the sample treated at 130 ° C. for 10 days was after 190 hours of each temperature atmosphere, after 183 cycles of H / C1, and after 175 cycles of H / C2. , −25 ° C., 25 ° C. (room temperature), 70 ° C., 100 ° C., H / C 1, H / C 2, the change in diffraction efficiency is small, and the first-order diffraction at the Bragg angle even with maximum stability The efficiency is about + 34% (the stability of the refractive index difference Δn is about + 18%).

In any of these cases, the modified length L does not change, and the wavelength 6 of the laser irradiation section is not changed.
Since the light transmittance at 32.8 nm is almost 90% or more as shown in Table 8, the change in the diffraction efficiency after each temperature atmosphere process was considered to be the change in the refractive index difference Δn.

Therefore, when the heat treatment is performed after laser irradiation, the first-order diffraction efficiency and the refractive index difference Δn at the Bragg angle are stabilized if the subsequent temperature and its fluctuation are equal to or lower than the heat treatment temperature, but the heat treatment temperature When the temperature fluctuation includes the above and the above, the diffraction efficiency changes depending on the temperature tendency during the heat treatment in Example 2, that is, the diffraction efficiency increases at 70 ° C. or higher and maximizes at 120 ° C. It can be seen that the efficiency and Δn are greatly changed. That is, in order to stabilize the refractive index difference Δn with respect to the subsequent temperature change of the optical element manufactured by the method of inducing the refractive index change inside the optical polymer structure by femtosecond laser irradiation, use of the optical element is required. The absolute temperature display T _{1 of the} highest temperature that is sometimes exposed is 0.8 ≦ T ₁ / T _g ≦
When included in 1.13, it was found that the heat treatment should be performed at a temperature of T ₁ ≦ T as the heating temperature T after the femtosecond laser irradiation.

(Example 8)
In this example, first, the same conditions as in Example 3 were set inside the optical polymer structure. As a result, the modified thickness L was 160 μm, the Q value obtained by the equation (4) was 4.2, and the first-order diffraction efficiency at the Bragg angle was 0.1%. The refractive index difference Δn between the laser irradiated part and the non-irradiated part was 0.7 × 10 ⁻⁴ , and the light transmittance at a wavelength of 632.8 nm of the laser irradiated part was 99%.

Thereafter, a lapse process was performed for 10 days in each temperature atmosphere of 25 ° C. (room temperature), 70 ° C., and 100 ° C. The atmosphere at 70 ° C. and 100 ° C. was adjusted by a constant temperature heating tank. When the measurement is carried out at 25 ° C. (room temperature) after the treatment, the first-order diffraction efficiency at the Bragg angle after 10 days of treatment at 25 ° C. (room temperature) is 7.2%. The refractive index difference Δn is 6.9 × 10 ⁻⁴ , the light transmittance at a wavelength of 632.8 nm of the laser irradiation part is 96%, and 1 at the Bragg angle after 10 days of processing at 70 ° C. The next diffraction efficiency is 14.7%, the refractive index difference Δn between the laser irradiated part and the non-irradiated part is 9.9 × 10 ⁻⁴ , and the light transmittance at the wavelength of 632.8 nm of the laser irradiated part is 98%. Further, the first-order diffraction efficiency at the Bragg angle after 10 days of processing at 100 ° C. is 11.5%, the refractive index difference Δn between the laser irradiation part and the non-irradiation part is 8.7 × 10 ⁻⁴ , and laser irradiation The light transmittance of the part at a wavelength of 632.8 nm was 95%.

  Further, after that, each of the optical polymer structures subjected to the above treatment was subjected to 190 hours in each temperature atmosphere at −25 ° C., 25 ° C. (room temperature), 70 ° C., and 100 ° C., and in a temperature cycle atmosphere of H / C1. After the progress treatment was performed under the conditions of 183 cycles and 175 cycles in an H / C2 temperature cycle atmosphere, the measurement was performed at 25 ° C. (room temperature). Tables 9 and 10 show that after the laser irradiation, the first-order diffraction efficiency and the laser irradiation part after exposure to the atmospheric conditions at each temperature after 10 days at temperatures of 25 ° C. (room temperature), 70 ° C., and 100 ° C. The light transmittance at a wavelength of 632.8 nm is shown. In addition, FIG. 12 shows a graph of the first-order diffraction efficiency after exposure to various atmospheric conditions after 10 days at 25 ° C. (room temperature) after laser irradiation. Further, FIG. 13 shows a graph of the first-order diffraction efficiency after exposure to each temperature and atmosphere condition after 10 days at 70 ° C. after laser irradiation. Further, FIG. 14 shows a graph of the first-order diffraction efficiency after exposure to each temperature and atmosphere condition after 10 days at 100 ° C. after laser irradiation. Among each temperature atmosphere condition, −25 ° C. was adjusted by a constant temperature cooling bath, 70 ° C. and 100 ° C. by a constant temperature heating bath, and H / C1 and H / C2 were adjusted by a heat cycle test bath.

  As is apparent from Table 9 and FIG. 12, the sample treated at 25 ° C. (room temperature) for 10 days was after 190 hours of each temperature atmosphere, 183 cycles of H / C1, and 175 cycles of H / C2. Later, at −25 ° C. and 25 ° C. (room temperature), the maximum stability is obtained, and the first-order diffraction efficiency at the Bragg angle is about + 18% (+ 9% as the stability of the refractive index difference Δn). At 100 ° C., H / C1, H / C2, the diffraction efficiency changes greatly, and the maximum stability is about + 125% as the first-order diffraction efficiency at the Bragg angle (+ 52% as the stability of the refractive index difference Δn). Become.

  Further, as is apparent from Table 9 and FIG. 13, the samples treated at 70 ° C. for 10 days were observed after 190 hours after each temperature atmosphere, after 183 cycles of H / C1, and after 175 cycles of H / C2. , −25 ° C., 25 ° C. (room temperature), 70 ° C., and H / C1, the change in diffraction efficiency is small, and even with the maximum stability, the first-order diffraction efficiency at the Bragg angle is −9% (refractive index difference Δn Although the stability is about −5%), the diffraction efficiency changes at 100 ° C. and H / C2, and the maximum stability, the first-order diffraction efficiency at the Bragg angle is −19% (the refractive index difference Δn is stable) About -10%).

  Further, as is apparent from Table 9 and FIG. 14, the samples treated at 100 ° C. for 10 days were processed after 190 hours of each temperature atmosphere, after 183 cycles of H / C1, and after 175 cycles of H / C2. , −25 ° C., 25 ° C. (room temperature), 70 ° C., 100 ° C., H / C 1, H / C 2, the change in diffraction efficiency is the maximum stability, the first-order diffraction efficiency at the Bragg angle As + 26% (+ 13% as the stability of the refractive index difference Δn).

  In any of these cases, the modified length L does not change, and the light transmittance at a wavelength of 632.8 nm of the laser irradiation portion hardly changes at 90% or more as shown in Table 10. The change in the diffraction efficiency after the temperature atmosphere process was considered as the change in the refractive index difference Δn.

Therefore, when heat treatment is performed after laser irradiation, the first-order diffraction efficiency and the refractive index difference Δn at the Bragg angle are stable if the subsequent temperature and its fluctuation are equal to or lower than the heat treatment temperature,
When the temperature variation including the above-mentioned heat treatment temperature or higher is included, it depends on the temperature tendency at the time of heat treatment in Example 3, that is, the diffraction efficiency increases at 50 ° C. or higher and maximizes at 70 ° C. or maximizes at 100 ° C. It can be seen that the diffraction efficiency and Δn are greatly changed. In this example, it was processed at 70 ° C., as seen in Example 3, that the difference in diffraction efficiency was not large even if the treatment was performed at 70 ° C. for 10 days and then at 100 ° C. for 190 hours. This is because the difference in diffraction efficiency obtained between the case of processing at 100 ° C. and the case of processing at 100 ° C. is not so large. That is, in order to stabilize the refractive index difference Δn with respect to the subsequent temperature change of the optical element manufactured by the method of inducing the refractive index change inside the optical polymer structure by femtosecond laser irradiation, use of the optical element is required. The absolute temperature display T _{1 of the} highest temperature that is sometimes exposed is 0.8
When included in ≦ T ₁ / T _g ≦ 1.13, it was found that the heat treatment should be performed at the temperature T ₁ ≦ T as the heating temperature T after the femtosecond laser irradiation.

Example 9
In this example, first, the femtosecond laser was focused and irradiated inside the optical polymer structure under the same conditions as in Example 5. As a result, the modified thickness L was 240 μm, the Q value was 6.4 according to Equation (4), and the first-order diffraction efficiency at the Bragg angle was 1.0%. The refractive index difference Δn between the laser irradiated part and the non-irradiated part was 1.7 × 10 ⁻⁴ , and the light transmittance at a wavelength of 632.8 nm of the laser irradiated part was 98%.

Thereafter, a lapse treatment was performed for 8 days in each temperature atmosphere of 25 ° C. (room temperature), 70 ° C., and 100 ° C. The atmosphere at 70 ° C. and 100 ° C. was adjusted by a constant temperature heating tank. When measurement was performed at 25 ° C. (room temperature) after the treatment, the first-order diffraction efficiency at the Bragg angle after 8 days of treatment at 25 ° C. (room temperature) was 1.2%. The refractive index difference Δn is 1.9 × 10 ⁻⁴ , the light transmittance of the laser irradiation part at a wavelength of 632.8 nm is 98%, and 1 at the Bragg angle after 8 days of processing at 70 ° C. The next diffraction efficiency is 31.7%, the refractive index difference Δn between the laser irradiated portion and the non-irradiated portion is 10.0 × 10 ⁻⁴ , and the light transmittance at the wavelength of 632.8 nm of the laser irradiated portion is 98%. Further, the first-order diffraction efficiency at the Bragg angle after 8 days of processing at 100 ° C. is 1.5%, the refractive index difference Δn between the laser irradiation part and the non-irradiation part is 2.0 × 10 ⁻⁴ , and laser irradiation The light transmittance of the part at a wavelength of 632.8 nm was 98%.

  Further, after that, each of the optical polymer structures subjected to the above-described treatment was subjected to 240 hours in a temperature atmosphere of −25 ° C., 25 ° C. (room temperature), 70 ° C., and 100 ° C. in a temperature cycle atmosphere of H / C1. After lapse of 239 cycles and 224 cycles in an H / C2 temperature cycle atmosphere, measurement was performed at 25 ° C. (room temperature). Tables 11 and 12 show that after the laser irradiation, the first-order diffraction efficiency and the laser irradiation portion after exposure to each temperature atmosphere condition after 8 days at temperatures of 25 ° C. (room temperature), 70 ° C., and 100 ° C. The light transmittance at a wavelength of 632.8 nm is shown. FIG. 15 shows a graph of the first-order diffraction efficiency after exposure to various atmospheric conditions after 8 days at 25 ° C. (room temperature) after laser irradiation. In addition, FIG. 16 shows a graph of the first-order diffraction efficiency after exposure to each temperature and atmosphere condition after 8 days at 70 ° C. after laser irradiation. In addition, FIG. 17 shows a graph of the first-order diffraction efficiency after exposure to various atmospheric conditions after 10 days at 100 ° C. after laser irradiation. Among each temperature atmosphere condition, −25 ° C. was adjusted by a constant temperature cooling bath, 70 ° C. and 100 ° C. by a constant temperature heating bath, and H / C1 and H / C2 were adjusted by a heat cycle test bath.

  As is apparent from Table 11 and FIG. 15, the sample treated at 25 ° C. (room temperature) for 8 days was obtained after 240 hours of each temperature atmosphere, 239 cycles of H / C1, and 224 cycles of H / C2. Later, at −25 ° C. and 25 ° C. (room temperature), the first-order diffraction efficiency at the Bragg angle is about −40% (the stability of the refractive index difference Δn is about −23%). At 70 ° C., 100 ° C., H / C1, and H / C2, the diffraction efficiency changes greatly. With the maximum stability, the first-order diffraction efficiency at the Bragg angle is + 1250% (the stability of the refractive index difference Δn is + 300%). It will be about.

  Further, as is apparent from Table 11 and FIG. 16, the samples treated at 70 ° C. for 8 days were obtained after 240 hours of each temperature atmosphere, after 239 cycles of H / C1, and after 224 cycles of H / C2. , −25 ° C., 25 ° C. (room temperature), 70 ° C., and H / C1, the change in diffraction efficiency is small, and even with the maximum stability, the first-order diffraction efficiency at the Bragg angle is −9% (refractive index difference Δn Although the stability is about −5%), the diffraction efficiency changes greatly at 100 ° C. and H / C2, and the maximum stability, the first-order diffraction efficiency at the Bragg angle is −98% (with a refractive index difference Δn). The stability is about -89%).

  In addition, as is apparent from Table 11 and FIG. 17, the samples treated at 100 ° C. for 8 days were obtained after 240 hours of each temperature atmosphere, after 239 cycles of H / C1, and after 224 cycles of H / C2. , −25 ° C., 25 ° C. (room temperature), 70 ° C., 100 ° C., H / C 1, H / C 2, the change in diffraction efficiency is small, and the first-order diffraction at the Bragg angle even with maximum stability The efficiency is about -23% (the stability of the refractive index difference Δn is about -12%).

  In any of these cases, the modified length L does not change, and the light transmittance at a wavelength of 632.8 nm of the laser irradiation portion hardly changes at 90% or more as shown in Table 12. The change in the diffraction efficiency after the temperature atmosphere process was considered as the change in the refractive index difference Δn.

Therefore, when heat treatment is performed after laser irradiation, the first-order diffraction efficiency and the refractive index difference Δn at the Bragg angle are stable if the subsequent temperature and its fluctuation are equal to or lower than the heat treatment temperature,
When the temperature variation including the above processing temperature at the time of heating and the above is included, the diffraction efficiency change depending on the temperature tendency at the time of the heat processing in Example 5, that is, the tendency that the diffraction efficiency increases at 50 ° C. or higher and maximizes at 70 ° C. It can be seen that the diffraction efficiency and Δn are greatly changed. That is, in order to stabilize the refractive index difference Δn with respect to the subsequent temperature change of the optical element manufactured by the method of inducing the refractive index change inside the optical polymer structure by femtosecond laser irradiation, use of the optical element is required. The absolute temperature display T _{1 of the} highest temperature that is sometimes exposed is 0.8 ≦ T ₁ / T _g ≦ 1
. 13 included, it was found that the heat treatment should be performed at the temperature T ₁ ≦ T as the heating temperature T after the femtosecond laser irradiation.

(Raman spectroscopy)
In order to elucidate the reason why the difference in refractive index between the irradiated part and the non-irradiated part is enlarged and stabilized by performing heat treatment after irradiation of the femtosecond laser inside the optical polymer structure, the optical polymer in Example 1 is used. Two samples were prepared with and without heat treatment after the femtosecond laser irradiation in the structure and processing conditions, and these samples were subjected to Raman spectroscopic analysis, and the obtained Raman spectra were compared. However, the processing conditions were such that the femtosecond laser was irradiated under the same conditions as in Example 1 except that the laser pulse energy on the processed surface was 700 nJ and the period Λ was 6 μm. Moreover, what heat-processed after laser irradiation was made into the heat processing for 5 days at 70 degreeC. As a result of Raman spectrum, FIG. 18 shows the case where the heat treatment is not performed after the femtosecond laser irradiation, and FIG. 19 shows the case where the heat treatment is performed at 70 ° C. for 5 days after the femtosecond laser irradiation. 18 and 19, (a) in FIGS. 18 and 19 is a Raman spectrum in the laser irradiation part, (b) in FIGS. 18 and 19 is a Raman spectrum in the non-irradiation part, and (c) in FIG. 18 and FIG. 19. ) Indicates the difference between the two spectra.

  From the comparison between FIG. 18 and FIG. 19, the laser irradiation part, the non-irradiation part, and the difference spectrum thereof show the same spectral tendency both in the case where the heat treatment is performed after the laser irradiation and in the case where the heat treatment is not performed. It is confirmed that there is almost no change in the state.

On the other hand, when comparing the laser irradiated portion and the non-irradiated portion, in the laser irradiated portion, the Raman peak (2953, 1732, 1445, 987, 816, 604 cm ⁻¹ ) derived from the acrylic group is negative, while the methyl group (2982 cm). ^-1 ) and a peak corresponding to a methylene group (2913 cm ^-1 ) were observed positively, and a new Raman peak (1643 cm ^-1 ) of a carbon double bond (C = C) appeared. Thus, it is confirmed that the chemical bonding state in the polymer changes in the laser irradiation part. For example, it is inferred that the molecular weight is reduced by cutting the side chain, or the molecular weight is reduced by cutting the main chain.

  From the above Raman spectroscopic analysis results, almost no chemical change was observed, so it was inferred that the expansion and stabilization of the refractive index difference due to heat treatment after laser irradiation was due to structural changes. . It was also inferred that one of the reasons why the structural change is different between the non-irradiated part and the irradiated part is that the chemical bonding state in the polymer of the irradiated part changes.

(Phase image measurement by atomic force microscope)
Next, in order to investigate the phenomenon as a structural change, phase images of the same sample as the Raman spectroscopic analysis were measured with an atomic force microscope, and phase images with and without heating after laser irradiation were compared. As a result of the atomic force microscope phase image, FIG. 20 shows the case where the heat treatment is not performed after the femtosecond laser irradiation, and FIG. 21 shows the case where the heat treatment is performed at 70 ° C. for 5 days after the femtosecond laser irradiation. 20 and 21, A in the figure indicates a laser irradiation part, and B in the figure indicates a non-irradiation part.

20 and FIG. 21 confirms that the laser irradiation portion tends to be thinner when the heat treatment is performed after the laser irradiation than when there is no heat treatment, and the laser irradiation portion tends to shrink due to the heat treatment. It is inferred.

  Therefore, the heat treatment after the femtosecond laser irradiation inside the optical polymer structure increases and stabilizes the refractive index difference between the irradiated part and the non-irradiated part due to structural contraction of the laser irradiated part. It is inferred that the density increases.

  In addition, one reason for the structural shrinkage and the increase in density was presumed that the chemical bonding state of the femtosecond laser irradiated part was changed, and the volume relaxation was promoted as compared with the non-irradiated part.

  It should be understood that the embodiments and examples disclosed herein are illustrative and non-restrictive in every respect. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  For example, an optical element having a high diffraction efficiency or an optical element having an optical waveguide with a small propagation loss when the radius of curvature is small can be provided.

It is a figure which shows the time-dependent change of the 1st-order diffraction efficiency in Example 1. FIG. It is a figure which shows the time-dependent change of the 1st order diffraction efficiency in Example 2. FIG. FIG. 6 is a graph showing a change with time in first-order diffraction efficiency in Example 3. It is a figure which shows the 1st-order diffraction efficiency after 7-day progress in Example 4, and the visible ray transmittance of a laser irradiation part. It is a figure which shows the daily change of the 1st-order diffraction efficiency in Example 5. FIG. In Example 6, it is a figure which shows the 1st-order diffraction efficiency after exposure to each temperature atmosphere after progress for 7 days at 25 degreeC (room temperature) after femtosecond laser irradiation. In Example 6, it is a figure which shows the 1st-order diffraction efficiency after exposure to each temperature atmosphere after progress for 7 days at 70 degreeC after femtosecond laser irradiation. In Example 6, it is a figure which shows the 1st-order diffraction efficiency after exposure to each temperature atmosphere after progress for 7 days at 100 degreeC after femtosecond laser irradiation. It is a figure which shows the 1st-order diffraction efficiency after exposure to each temperature atmosphere after progress for 10 days at 25 degreeC (room temperature) after femtosecond laser irradiation in Example 7. FIG. It is a figure which shows the 1st-order diffraction efficiency after exposing to each temperature atmosphere after progress for 10 days at 70 degreeC after femtosecond laser irradiation in Example 7. FIG. It is a figure which shows the 1st-order diffraction efficiency after exposing to each temperature atmosphere after progress for 10 days at 130 degreeC after femtosecond laser irradiation in Example 7. FIG. It is a figure which shows the 1st-order diffraction efficiency after exposing to each temperature atmosphere after progress for 10 days at 25 degreeC (room temperature) after femtosecond laser irradiation in Example 8. FIG. It is a figure which shows the 1st-order diffraction efficiency after exposing to each temperature atmosphere after progress for 10 days at 70 degreeC after femtosecond laser irradiation in Example 8. FIG. It is a figure which shows the 1st-order diffraction efficiency after exposing to each temperature atmosphere after progress for 10 days at 100 degreeC after femtosecond laser irradiation in Example 8. FIG. In Example 9, it is a figure which shows the 1st-order diffraction efficiency after exposure to each temperature atmosphere after progress for 8 days at 25 degreeC (room temperature) after femtosecond laser irradiation. In Example 9, it is a figure which shows the 1st-order diffraction efficiency after exposing to each temperature atmosphere after progress for 8 days at 70 degreeC after femtosecond laser irradiation. In Example 9, it is a figure which shows the 1st-order diffraction efficiency after exposure to each temperature atmosphere after progress for 8 days at 100 degreeC after femtosecond laser irradiation. It is a spectrum which shows the result of having conducted the Raman spectroscopic analysis in the case of not performing heat processing after femtosecond laser irradiation on the conditions of Example 1, (a) is a Raman spectrum in a laser irradiation part, (b) is a non-irradiation part. (C) is the difference spectrum of both spectra. It is a spectrum which shows the result of having performed the Raman spectroscopic analysis at the time of heating for 5 days at 70 degreeC after the femtosecond laser irradiation in Example 1, (a) is a Raman spectrum in a laser irradiation part, (b) is The Raman spectrum in the non-irradiated part, (c) is the difference spectrum of both spectra. 2 is a diagram showing a phase image by an atomic force microscope when heat treatment is not performed after femtosecond laser irradiation in Example 1. FIG. It is a figure which shows the phase image by an atomic force microscope at the time of heating for 5 days at 70 degreeC after the femtosecond laser irradiation in Example 1. FIG.

Claims (12)

A laser irradiation step of changing the refractive index of the irradiated portion by irradiating the inside of the optical polymer structure with a femtosecond laser having a pulse width of 10 ^-15 seconds to 10 ^-11 seconds;
A heating step of heating the optical polymer structure after the laser irradiation ,
The heating step, and T the heating temperature in absolute temperature, when the absolute temperature of the glass transition point of the material constituting the optical polymeric structure and T _g, of 0.8 ≦ T / T _g ≦ 1.13 The manufacturing method of the optical element heated on condition.   The method of manufacturing an optical element according to claim 1, wherein the heating in the heating step is 30 seconds or more. The method for manufacturing an optical element according to claim 1, wherein the heating in the heating step is 24 hours or more. The heating temperature T is within ± 10K of the absolute temperature of the temperature at which the difference in refractive index between the irradiated part and the non-irradiated part becomes maximum in heating for a predetermined time, and the time for which the difference in refractive index is saturated is the shortest. within ± 10K of absolute temperature, and the time difference in the refractive index is maximized is described in any one of claims 1 to 3 temperature is any temperature absolute temperature of ± 10K within in the shortest A method for manufacturing an optical element. The method of manufacturing an optical element according to claim 4, wherein the predetermined time is 168 hours. The heating temperature T is 0 . When in the range of _{8 ≦ 343 / T g ≦ 1.13} , method of manufacturing an optical element according to any one of claims 1 to 5, 343 ≦ T. The heating temperature T is 0.8 ≦ 373 / T. _g The method for manufacturing an optical element according to claim 1, wherein 373 ≦ T is satisfied in the range of ≦ 1.13. The material constituting the optical polymer structures, polymethyl methacrylate, polycarbonate, and method of manufacturing an optical element according to any one of claims 1 to 7 at least one selected from the group consisting of a cycloolefin polymer . The optical polymer structure is composed of a mixture containing a base material and an additive,
The base material is polymethylmethacrylate;
The additive is a diarylethene having a structure represented by the following formula (1):
The method for manufacturing an optical element according to any one of claims 1-8 mixing ratio of the additive material relative to the base material is 3% by mass or more.
(In the formula (1), R ₁ and R ₄ are an aliphatic hydrocarbon group, a hydroxy group, a nitro group, an amino group or a mercapto group. R ₂ , R ₃ , R ₅ and R ₆ are hydrogen, A substituent selected from the group consisting of an amino group, an aliphatic hydrocarbon group, an aromatic hydrocarbon group, and an aromatic heterocyclic group, or R ₂ and R ₃ , and R ₅ and R ₆ are aromatic carbonized It may constitute hydrogen or an aromatic heterocyclic ring, X and Y are sulfur, nitrogen or oxygen, and ring Z has a structure consisting of alicyclic hydrocarbon, aromatic hydrocarbon or aromatic heterocyclic ring .) An optical element manufactured by the manufacturing method of an optical element according to any one of claims 1 to 9 optical element refractive index difference between the irradiated portion and the non-irradiated portion is 0.0002 or more. An optical element manufactured by the method for manufacturing an optical element according to any one of claims 1 to 9 , wherein a difference in refractive index between an irradiated part and a non-irradiated part is stable against a temperature change at a heating temperature T or less. An optical element that is ± 30% or less. The optical element according to claim 10 or 11 , wherein the irradiating unit has a light transmittance of a working wavelength at a thickness of 0.3 mm of the irradiating unit of 80% or more.