JP2539850B2 - Nonlinear optical material and nonlinear optical element using the same - Google Patents

Description

TECHNICAL FIELD The present invention relates to a non-linear optical material and a non-linear optical element using the same, and more specifically, it contains at least a biphenyl-based compound which is preferably used in the field of optoelectronics. And a nonlinear optical element using the same.

<Problems to be Solved by Prior Art and Invention> The non-linear optical effect is a phenomenon in which, when light enters a medium, polarization proportional to the second-order or higher-order term of the electric field of the light occurs, A non-linear optical effect appears remarkably under a strong electric field such as light. This nonlinear optical effect enables generation of the second harmonic, Kerr effect, optical bistability, etc. Especially, the second-order nonlinear optical effect occurring in proportion to the square of the electric field of light is an optical wavelength conversion element or an optical modulation element. Since it can be applied to non-linear optical elements such as the above, which can be applied to elements that promise the development of the optoelectronics field, they have received much attention.

The materials that make up these devices are currently KH ₂ PO ₄
Only some inorganic materials such as (KDP) are in practical use. However, the non-linear optical constants of these inorganic materials are small, and therefore extremely high voltage or extremely high light intensity is required for the operation of the device. Therefore, the demand for materials having large nonlinear optical constants is extremely strong, and various materials have been searched for. Among inorganic materials, lithium niobate (LiNbO ₃ ) has the largest nonlinear optical constant, but lithium niobate causes a partial change in the refractive index when irradiated with a strong laser beam, and is easily exposed to light. It has the drawback of being damaged and has not yet been put to practical use.

Recently, it has been found that organic materials have much higher nonlinear optical properties than inorganic materials, such as 2-methyl-4-nitroaniline (MNA).
As typified by, a material having a π-electron system, an electron-donating group and an electron-withdrawing group in the molecule, and an extremely large nonlinear optical constant is drawing attention. But,
In order to obtain the second-order nonlinear optical effect, it is necessary that the crystal structure does not have an inversion symmetry center, and it is ideal that the molecules in the crystal are arranged in one direction. It is extremely difficult to control the crystal structure of a compound having an optical constant β (hereinafter referred to as a non-linear optical constant β) larger than that of MNA in a molecular state, that is, a compound having a larger permanent dipole moment or a larger π electron system. It has been difficult to report an organic compound having a second-order nonlinear optical effect higher than that of MNA, and thus, a nonlinear optical material and a nonlinear optical element having a higher efficiency than MNA have not been known.

<Object> The present invention has been made in view of the above problems, and an object of the present invention is to provide an organic nonlinear optical material having a high nonlinear optical effect and a nonlinear optical element using the same.

<Means and Actions for Solving Problems> The nonlinear optical material of the first invention is characterized by containing at least a compound represented by the following general formula [I].

(In the formula, R ¹ and R ² are electron withdrawing atoms or electron withdrawing groups, R ³ and R ⁴ are linear or branched alkyl groups or alkoxy groups, and X is a substituent having a hydrogen bondable hydrogen atom. In the organic nonlinear optical material, in order to increase the nonlinear optical constant β, it is necessary that electron transfer in the molecule smoothly progresses when polarization occurs due to the electric field of light,
It is said that the second-order nonlinear optical material must be a material whose molecular arrangement does not have a center of symmetry, but the first invention has the above-mentioned constitution and is represented by the general formula [I]. In a biphenyl compound, a benzene skeleton having an electron-withdrawing atom or an electron-withdrawing group is bonded to a benzene skeleton substituted with a substituent having a hydrogen-bondable hydrogen atom exhibiting an electron-donating property, resulting in an electron transition. Since this is an intramolecular charge transfer type compound in which electrons largely move, a non-linear optical constant β at the molecular level is large and a remarkable non-linear optical effect is exhibited. Further, the crystal structure can be controlled by adjusting the bulkiness of each substituent together with the substituent having a hydrogen atom capable of hydrogen bonding which functions as an electron donating group.

In the biphenyl-based compound represented by the general formula [I], R ¹ and R ² are nitro group, cyano group, cyanoalkyl group, cyanoalkoxycarbonylalkyl group, cyanoalkoxycarbonylalkenyl group, halogen atom, halogen atom. Optionally substituted alkanesulfonyl group, sulfo group, esterified sulfo group, carboxy group, esterified carboxy group, acyl group, optionally substituted carbamoyl group, and optionally substituted group. Optionally an electron-withdrawing atom or electron-withdrawing group selected from the group consisting of sulfamoyl groups, R ³ and R ⁴ are linear or branched lower alkyl groups or lower alkoxy groups, and X is hydroxy. Group, mercapto group, amino group, imino group, carboxy group, carbamoyl group, hydroxyalkyl group, hydroxy Amino group and hydroxyimino compound is a substituent selected from the group consisting of groups, large electron mobility, preferably in order to increase the nonlinear optical constant beta, also the substituents hydrogen bond with each substituent X R ¹ ,
The crystal structure can be controlled by the bulkiness of R ² , R ³ and R ⁴ .

In particular, R ¹ and R ² are 2-position and 4-position of the benzene ring.
A compound in which R ³ and R ⁴ are substituted in the 3-position and 5-position of the benzene ring has a larger nonlinear optical constant β and the crystal structure is easily controlled.

Furthermore, the compound represented by the general formula [I] is 3,5-
Dimethyl-2 ', 4'-dinitro-1,1'-biphenyl-
4-ol and 3,5-di-tert-butyl-2 ', 4'-dinitro-1,1'-biphenyl-4-ol are hydrogen bonds based on hydroxyl groups and bulky alkyl groups. The crystal structure is controlled by and, the nitro group exhibits electron-withdrawing property, and the hydroxy group and the alkyl group show electron-donating property. Therefore, the electron largely moves with the electronic transition, and the nonlinear optical constant β is It is large and brings about a remarkable nonlinear optical effect even in a crystalline state.

Further, the single-component crystal of the compound represented by the general formula [I] exhibits a large non-linear optical effect.

A nonlinear optical element of a second invention is a nonlinear optical element having an optical waveguide section, wherein the optical waveguide section is composed of a nonlinear optical material containing at least the compound represented by the general formula [I]. It is characterized by being

According to the nonlinear optical element having the above-described configuration, the optical waveguide portion is made of the nonlinear optical material containing at least the compound represented by the general formula [I] having a large nonlinear optical constant. It is possible to obtain a second-order non-linear optical element having a large intensity, it is possible to separate a high intensity second harmonic even with a laser beam having a weak intensity, and it is possible to efficiently produce an electro-optical effect even with a small voltage change.

 Hereinafter, the first invention will be described in detail.

In the compound represented by the above general formula [I], R ¹ and R ² represent an electron withdrawing atom or an electron withdrawing group. Examples of the electron-withdrawing atom or electron-withdrawing group include a hydrogen atom; a nitro group; a cyano group; a cyanoalkyl group such as cyanomethyl, cyanoethyl, and cyanopropyl; cyanomethoxycarbonylmethyl, cyanoethoxycarbonylmethyl, cyanopropoxycarbonylmethyl, 2 -Cyano-2-methoxycarbonylethyl, 2-cyano-2-ethoxycarbonylethyl, 2-cyano-2-propoxycarbonylethyl, 2-cyano-2-butoxycarbonylethyl, 3-cyano-3-methoxycarbonylpropyl, 3 -Cyano-3-ethoxycarbonylpropyl, 3
-Cyano-3-propoxycarbonylpropyl, 3-cyano-3-butoxycarbonylpropyl, 4-cyano-
Cyanoalkoxycarbonylalkyl groups such as 4-ethoxycarbonylbutyl; 2-cyano-2-methoxycarbonylvinyl, 2-cyano-2-ethoxycarbonylvinyl, 2-cyano-2-propoxycarbonylvinyl, 2
-Cyano-2-butoxycarbonylvinyl, 2-cyano-1-methyl-2-methoxycarbonylvinyl, 2-cyano-1-methyl-2-ethoxycarbonylvinyl, 2
Cyanoalkoxycarbonylalkenyl groups such as -cyano-1-methyl-2-propoxycarbonylvinyl, 2-cyano-1-methyl-2-butoxycarbonylvinyl and 3-cyano-3-methoxycarbonylallyl; fluorine, chlorine, bromine, Halogen atom such as iodine; methanesulfonyl, ethanesulfonyl, propanesulfonyl, butanesulfonyl, trifluoromethanesulfonyl, 2,2,
Alkanesulfonyl group optionally having a halogen atom such as 2-trifluoroethanesulfonyl; sulfo group;
Substituents such as methoxysulfonyl, ethoxysulfonyl, propoxysulfonyl, isopropoxysulfonyl, butoxysulfonyl, tert-butoxysulfonyl, pentyloxysulfonyl, hexyloxysulfonyl, octyloxysulfonyl, and other alkoxysulfonyl, phenoxysulfonyl, p-cyanophenoxysulfonyl, etc. Optionally esterified sulfo group such as phenoxysulfonyl; carboxy group; methoxycarbonyl, ethoxycarbonyl, propoxycarbonyl, isopropoxycarbonyl, butoxycarbonyl, isobutoxycarbonyl, tert-butoxycarbonyl, hexyloxycarbonyl, octyl Alkoxycarbonyl groups such as oxycarbonyl, phenoxycarbonyl, p-nitrophenoxycal Esterified carboalkyl groups such as aralkyloxycarbonyl such as aryloxycarbonyl, benzyloxycarbonyl and benzhydryloxycarbonyl, which may have a substituent such as nyl; formyl, acetyl, propionyl, butyryl, hexanoyl, benzoyl An acyl group such as; carbamoyl, methylcarbamoyl, dimethylcarbamoyl, ethylcarbamoyl, propylcarbamoyl, phenylcarbamoyl, benzylcarbamoyl, and other optionally substituted carbamoyl groups; sulfamoyl, methylsulfamoyl, ethylsulfamoyl, It may have a substituent such as phenylsulfamoyl, benzylsulfamoyl and the like, and thus examples thereof include a sulfamoyl group; a nitroso group; a sulfino group; and a thiocarboxy group.

Among the electron-withdrawing atoms or electron-withdrawing groups, a nitro group, a cyano group, a cyanoalkyl group, a cyanoalkoxycarbonylalkyl group, a cyanoalkoxycarbonylalkenyl group, a halogen atom, an alkanesulfonyl group which may have a halogen atom. , A sulfo group, an esterified sulfo group, a carboxy group, an esterified carboxy group, an acyl group, a carbamoyl group which may have a substituent and a sulfamoyl group which may have a substituent Electron-withdrawing atom or electron-withdrawing group selected from, especially large electron-withdrawing nitro group, cyano group,
A cyanoalkoxycarbonylalkenyl group, a fluorine atom, a carboxy group, an esterified carboxy group, an acyl group, and among them, a nitro group is preferable.

Further, in the compound represented by the general formula [I], R ¹ and R ² may be substituted at appropriate positions on the benzene ring, but in order to enhance the electron withdrawing property and increase the nonlinear optical constant β. , Those substituted at the 2- and 4-positions of the benzene ring are preferred.

Further, in the compound represented by the general formula [I], R ³ and R ⁴ represent a linear or branched alkyl group or an alkoxy group, and the alkyl group is methyl, ethyl, propyl, isopropyl, butyl. , Tert-butyl,
Examples include pentyl, hexyl and octyl groups. Further, as the linear or branched alkoxy group, methoxy, ethoxy, propoxy, isopropoxy, butoxy, isobutoxy, tert-butoxy, pentyloxy,
Hexyloxy and octyloxy groups are exemplified.
Among the above linear or branched alkyl groups and alkoxy groups, linear or branched lower alkyl groups and lower alkoxy groups having 1 to 6 carbon atoms, particularly methyl group having a large nonlinear optical constant β, tert-butyl Groups are preferred.

The substituents R ³ and R ⁴ may be substituted at appropriate positions on the benzene ring, but in order to increase the nonlinear optical constant β, they are substituted at the 3-position and 5-position of the benzene ring. Those that are present are preferable.

In the compound represented by the general formula [I], X
Represents a substituent having a hydrogen atom capable of hydrogen bonding. Examples of the substituent having a hydrogen atom capable of hydrogen bonding include a hydroxy group; a mercapto group; an amino group, methylamino,
Ethylamino, propylamino, isopropylamino,
Monoalkylamino groups such as butylamino, hexylamino and octylamino; monoaralkylamino groups such as benzylamino; monoarylamino groups such as phenylamino; imino groups; carboxy groups; carbamoyl groups; methylol, 2-hydroxyethyl, 3 -Hydroxyalkyl groups such as hydroxypropyl; hydroxyamino groups and hydroxyimino groups and the like. Among the substituents having hydrogen atoms capable of hydrogen bonding, a hydroxy group, a mercapto group, an amino group, an imino group, a carboxy group, a carbamoyl group, a hydroxyalkyl group, a hydroxyamino group and a hydroxyimino group, among others, a hydrogen bonding ability. Large hydroxy groups are preferred.

The compound represented by the general formula [I] is an intramolecular charge transfer type compound, has a large nonlinear optical constant β at the molecular level, and has a remarkable nonlinear optical effect. In addition, the crystal structure can be controlled by adjusting the bulkiness of each substituent together with the substituent having a hydrogen atom capable of hydrogen bonding which acts as an electron-donating group. The effect can be expressed. Among the compounds represented by the above general formula [I], 3,5-
Dimethyl-2 ', 4'-dinitro-1,1'-biphenyl-
4-ol, and 3,5-di-tert-butyl-2 ', 4'
-Dinitro-1,1'-biphenyl-4-ol has a crystal structure controlled by a hydrogen bond based on a hydroxyl group and the bulkiness of an alkyl group, and has a nitro group having an electron-withdrawing property and an electron-donating property. With the hydroxyl group and the alkyl group having, the electron mobility and the nonlinear optical constant β accompanying the electronic transition are particularly large, and a remarkable nonlinear optical effect is brought about.

The biphenyl compound represented by the general formula [I] is
For example, it can be produced by reacting a compound represented by the following general formula [II] with a compound represented by the following general formula [III].

(In the formula, R ¹ , R ² , R ³ , R ⁴ and X are the same as above.) The compound represented by the general formula [II] and the general formula [III]
The reaction for obtaining the compound represented by the general formula [I] from the compound represented by is usually carried out in an organic solvent, and any solvent can be used as long as it does not adversely affect the reaction. For example, aliphatic or alicyclic hydrocarbons such as n-hexane, n-octane and cyclohexane, aromatic hydrocarbons such as benzene, toluene and xylene, alcohols such as methanol, ethanol and propanol, acetone, Ketones such as methyl ethyl ketone,
Examples thereof include ethers such as diethyl ether, tetrahydrofuran and dioxane, acetonitrile, dimethylformamide, dimethylsulfoxide, hexamethylphosphoric triamide and the like. The reaction is usually carried out under heating to reflux, and the reaction is completed in about 30 minutes to 48 hours. After completion of the reaction, the reaction mixture can be concentrated and easily separated and purified by a conventional means such as recrystallization, solvent extraction, column chromatography and the like.

The nonlinear optical material containing at least the compound represented by the general formula [I] may be a single component crystal of the compound represented by the general formula [I], and is represented by the general formula [I]. It may be a mixed crystal or a mixed solid composed of a mixture of the compound and another nonlinear optical material or a liquid crystalline polymer. The compound represented by the general formula [I] has a substituent having a hydrogen atom capable of forming a hydrogen bond, and also has an electron-withdrawing group and an electron-donating group. The one-component crystal has a large nonlinear optical constant β even in the crystalline state and has a remarkable second-order nonlinear optical effect. Further, in the above-mentioned mixed crystal or mixed solid, the molecular arrangement in the crystal can be controlled to obtain a nonlinear material having a large second-order nonlinear optical effect.

As the other non-linear optical material, various organic non-linear optical materials are used, but a material having a large non-linear optical constant, for example, a second-order non-linear optical constant β of 5 × 10 5 is used.
-Compounds of ^-30 esu or more are used. As such an organic nonlinear optical material, a compound having an electron-withdrawing group and an electron-donating group in the molecule, for example, MNA, 1-methoxy-4- (4-nitrobenzylideneamino) benzene, 1-methoxy-4- (4-nitrobenzylideneamino) benzene, Methyl-4- (4-nitrobenzylideneamino) benzene, 1-ethyl-4- (4-nitrobenzylideneamino) benzene, 1-propyl-4- (4-nitrobenzylideneamino) benzene, 1-butyl-4-
(4-Nitrobenzylideneamino) benzene, 1- (4
Schiff base type compounds such as -nitrobenzylideneamino) -4-hexylbenzene, 1- (4-nitrobenzylideneamino) -4-octylbenzene, 1-ethyl-4- (4-cyanobenzylideneamino) benzene; 1-methyl Aminoanthraquinone, 2-methylaminoanthraquinone, 1,4-diamino-6-ethoxycarbonylanthraquinone, 1,4-diamino-2- (1-pyrrolidinyl)
Anthraquinone derivatives such as anthraquinone; ethyl 1,
Dithiol derivatives such as 3-dithiol-2-ylidene cyanoacetate and ethyl 4-methyl-1,3-dithiol-2-ylidene cyanoacetate; β, β-dicyano-4-methoxystyrene, β, β-dicyano- Styrene derivatives such as 4-methylstyrene; 2-bromo-4-nitro-N, N-dimethylaniline; 4-N, N-dimethylamino-
Examples include 4'-nitrostilbene; 2-ethylamino-1,3,4-thiadiazole and the like. The mixing ratio of the compound represented by the general formula [I] and the organic nonlinear optical material described above is such that desired optical properties and physical properties of the compound (for example, melting point,
It can be appropriately selected depending on the solubility, λmax, etc.).

A crystal consisting of a single component of the compound represented by the general formula [I] or a mixture crystal of the compound represented by the general formula [I] and the other non-linear optical material is, for example, ] A compound represented by the formula [1] is heated and melted, and then cooled to be crystallized; a method in which the compound is dissolved in an appropriate solvent at an appropriate temperature, and then the solvent is removed or the temperature is lowered to cause crystallization; Examples thereof include a method using a vapor deposition method such as vacuum deposition and molecular beam epitaxy. The first crystallization method may be a solution solidification method in which a melt of the compound represented by the general formula [I] is crystallized in a heating furnace having a temperature gradient during crystallization. The organic solvent used in the second crystallization method may be a polar solvent such as methanol or ethanol having a hydroxy group capable of hydrogen bonding, a polar solvent such as acetonitrile, ethyl acetate, diethyl ether or tetrahydrofuran, or benzene. It may be a nonpolar solvent or a small polar solvent such as toluene, or cyclohexane. At this time, if necessary, a solvent having an asymmetric carbon, for example, (R) -2-
Crystals may be obtained from a solvent having an asymmetric carbon such as butanol.

Examples of the liquid crystalline polymer include a side chain type liquid crystalline polymer having a mesogen group in the side chain, a side chain type polyacrylate type liquid crystal polymer, a side chain type polysiloxane type liquid crystal polymer and the like. By forming a solid mixture with the liquid crystalline polymer, the molecular orientation of the compound represented by the general formula [I] can be controlled by utilizing the molecular orientation of the liquid crystalline polymer.

Further, the solid mixture of the compound represented by the general formula [I] and the liquid crystalline polymer is gradually melted after the mixture of the compound represented by the general formula [I] and the liquid crystalline polymer is melted. To a liquid crystal state by cooling, then applying an electric field or magnetic field,
It is obtained by cooling and solidifying in that state. Since the liquid crystalline polymer is solidified in the aligned state by the application of an electric field or a magnetic field, it is possible to obtain a solid in a molecular arrangement state in which the compound represented by the general formula [I] does not have a center of symmetry.
In the mixture of the compound represented by the general formula [I] and the liquid crystalline polymer, the mixing ratio of the respective components should be such that the compound represented by the general formula [I] can be in a molecularly oriented solid state. It is not particularly limited, and can be appropriately selected depending on the properties of the compound represented by the general formula [I] and the liquid crystalline polymer used (for example, phase transition temperature, etc.). The content of the represented compound is about 2 to 60% by weight.

As described above, the nonlinear optical material containing at least the biphenyl compound represented by the general formula [I] has a large nonlinear optical constant β and has a remarkable nonlinear optical effect. Therefore, materials for nonlinear optical elements used in the field of optoelectronics, for example, materials for optical wavelength conversion elements, and optical modulation elements such as phase modulation elements, amplitude modulation elements, frequency modulation elements, pulse modulation elements, polarization wavefront modulation elements, etc. It is suitable as a material. Further, as the above-mentioned nonlinear optical material, the crystal itself of the compound represented by the general formula [I] can be used as an optical wavelength conversion element, but a waveguide type optical wavelength conversion element using the nonlinear optical material as an optical waveguide is used. [See J. Zyss, J. Molecular Electronics 1, 25 (1985), etc.]. By using a waveguide type optical wavelength conversion element, the light is confined in the waveguide, so the optical power density is increased, and the interaction length can be lengthened, resulting in higher efficiency and further mode Phase matching using dispersion is also possible.

<Embodiment> The first embodiment will be described below with reference to the accompanying drawings showing an embodiment.
A non-linear optical element using the non-linear optical material of the invention will be described in detail.

FIG. 1 shows an embodiment of the optical wavelength conversion element of the present invention,
1 is a schematic view of an optical fiber type optical wavelength conversion element as a second harmonic generation element, showing a core (1) made of a nonlinear optical material (hereinafter referred to as a nonlinear medium) containing at least a compound represented by the general formula [I]. ) Has a structure covered with a cladding (2) made of a medium such as glass (hereinafter, referred to as an isotropic medium) that does not exhibit a second-order nonlinear optical effect,
In the figure, the alternate long and short dash line indicates the fundamental wave of the incident light, and the alternate long and two short dashes line indicates the second harmonic. Light such as laser light is condensed by a lens or the like and is incident on the core (1) from one end surface of the light wavelength conversion element. The nonlinear medium forming the core (1) is large 2
Since the following nonlinear optical effect is exhibited, the light emitted from the other end surface of the core (1) includes a fundamental wave and a second harmonic wave, and the second harmonic wave is extracted by separating the light with a spectral means such as a prism or a filter. Be done.

2 and 3 are schematic diagrams showing other embodiments of the light wavelength conversion element, respectively, and in the drawings, the alternate long and short dash line and the alternate long and two short dashes line have the same meanings as in FIG. 1, respectively.

In the optical wavelength conversion element shown in the second figure, an optical waveguide section (2) made of a nonlinear medium is formed on a substrate (22) made of an isotropic medium.
1) is formed, and in the optical wavelength conversion element shown in FIG. 3, a substrate (32) made of an isotropic medium,
An optical waveguide portion (31) made of a non-linear medium is formed between it and a top layer (33) also made of an isotropic medium. The light wavelength conversion element described above is used in the same manner as the light wavelength conversion element shown in FIG.

Further, as the light modulation element, a device of a form conventionally used can be used. FIG. 4 shows, as an example thereof, a schematic view of an optical waveguide type optical modulation element of a lateral type operation as a phase modulation element, in which a substrate (4
A waveguide (41) made of a non-linear medium is provided in the inside of 2), and two electrodes (4) are provided through the waveguide (41).
3) are provided at opposite positions along the length direction, and an electric field is formed by applying a voltage between the electrodes (43). In the above element, when the light incident from one end of the waveguide section (41) in the length direction passes through the waveguide section (41) and is emitted from the other end surface, a nonlinear medium forming the waveguide section (41) When the refractive index of the light changes, the phase of the emitted light also changes. Since the refractive index of the non-linear medium changes depending on the applied voltage, by changing the applied voltage between the electrodes (43),
The phase of the emitted light can be modulated.

In the optical wavelength conversion element shown in FIGS. 1 to 4, the core (1) and the optical waveguides (21) (31) (41) are formed, for example, by using a nonlinear medium raw material and an isotropic medium, respectively. In a capillary consisting of, on a waveguide substrate made of an isotropic medium, or between waveguide substrates made of an isotropic medium, heating and melting, then slowly cooling to precipitate crystals, and vacuum deposition method on the substrate , A method of precipitating a crystal by a high frequency sputtering method or the like, and
A method of precipitating crystals from the solution in which the non-linear medium raw material is dissolved in an appropriate organic solvent in the above-mentioned capillary, on the substrate or between the substrates may be used. Further, in some cases, after processing the portion of the capillary, on or between the substrates, which is to be the contact interface with the nonlinear medium with the alignment treatment material, the nonlinear medium is precipitated and crystal grown to form an optical wavelength conversion element or the like. May be. As the alignment treatment material, an inorganic salt and an organic salt (for example, hexadecyltrimethylammonium bromide), a thin film made of an appropriate polymer (for example, polyamide), a metal complex, a metal thin film (for example, an obliquely evaporated gold thin film) Etc.) are exemplified.

The non-linear optical element of the present invention is not limited to the above-mentioned embodiment, and the light modulation element may be a vertical operation optical waveguide type light modulation element capable of amplitude modulation, or a non-linear crystal such as a crystal. It is also possible to adopt a form in which a voltage is directly applied to the medium itself. In the light modulation element, the electric field application direction for efficiently performing the phase modulation differs depending on the symmetry of the nonlinear medium, the direction of the crystal axis, and the like. Therefore, it is preferable to appropriately change the electrode configuration based on these.

Hereinafter, the present invention will be described in more detail based on specific examples.

Specific Example 1 1.2 g (30 mmol) of powdery sodium hydroxide, 4.1 g (20 mmol) of 2,6-di-tert-butylphenol and m-dinitrobenzene were added to 40 ml of dimethyl sulfoxide.
5.0 g (30 mmol) are added and stirred at a temperature of 80 ° C. for 2 hours. After completion of the reaction, the reaction mixture is poured into 400 ml of 1N hydrochloric acid aqueous solution and extracted 3 times with 400 ml of ethyl ether. The extract was dried with a desiccant, concentrated, separated by column chromatography, and recrystallized from n-hexane to give the desired product, 3,5-di-tert-butyl-2 ',
4'-dinitro-1,1'-biphenyl-4-ol 5.1 g
(Yield 69%) is obtained.

Melting point: 170-171 ° C ¹ H-NMR (CDCl ₃ ) δ: 1.47 (s, 18H), 5.52 (s, 1H), 7.20 (s, 2H), 7.7
0 (d, 1H, J = 9Hz), 8.41 (dd, 1H, J = 2Hz, 9H
z), 8.61 (d, 1H, J = 2Hz) IR (KBr): 3600, 2980, 1545, 1445, 1356, 1245cm ^-1 Mass spectrum (70eV) m / e (relative intensity): 372 (M ⁺ , 6 ) 357 (19), 52 (100), 41 (36) (see GPStahly, J.Org.Chem, _50, 3081 (1985)) The obtained crystal was irradiated with Nd: YAG laser light with a wavelength of 1.064 μm. However, light having a wavelength of 0.532 μm, which is the second harmonic, was observed.

Specific Example 2 2,6-Dimethylphenol was used in place of 2,6-di-tert-butylphenol in Specific Example 1, and 3,5-dimethyl-2 ′, 4 ′ was used in the same manner as in Specific Example 1 above. 2.8 g (yield 49%) of -dinitro-1,1'-biphenyl-4-ol are obtained.

Melting point: 182-183 ° C. ¹ H-NMR (CDCl ₃ ) δ: 2.28 (s, 6H), 4.90 (s, 1H), 6.98 (s, 2H), 7.61
(D, 1H, J = 9Hz), 8.43 (dd, 1H, J = 2Hz, 9H
z), 8.65 (d, 1H, J = 2Hz) IR (KBr): 3400, 1545, 1360cm ^-1 Mass spectrum (70eV) m / e (relative intensity): 315 (M ⁺ , 9), 73 (100) , 45 (24) When the obtained crystal was irradiated with Nd: YAG laser light having a wavelength of 1.064 μm, light having a wavelength of 0.532 μm, which was the second harmonic, was observed.

Example 3 After heating and melting the crystal obtained in Example 1, a glass capillary (inner diameter 5 to 10 μm, outer diameter 0.5 to 1 mm, length 2 to 3 c) was used.
After injecting into m) by utilizing a capillary phenomenon, crystals were grown in a Bridgman furnace to fabricate a light wavelength conversion element. When Nd: YAG laser light with a wavelength of 1.064 μm was irradiated from one end face of this element, generation of a second harmonic with a wavelength of 0.532 μm was observed from the other end face.

Specific Example 4 After melting the crystal obtained in Specific Example 2 by heating, a glass capillary (inner diameter 5 to 10 μm, outer diameter 0.5 to 1 mm, length 2 to 3 c)
After injecting into m) by utilizing a capillary phenomenon, crystals were grown in a Bridgman furnace to fabricate a light wavelength conversion element. When Nd: YAG laser light with a wavelength of 1.064 μm was irradiated from one end face of this element, generation of a second harmonic with a wavelength of 0.532 μm was observed from the other end face.

<Effects of the Invention> As described above, according to the nonlinear optical material of the first invention, the compound represented by the general formula [I] is an electron-withdrawing atom or an electron-withdrawing group, an electron-donating group, Since the crystal structure can be controlled by adjusting the bulkiness of each substituent and a substituent having a hydrogen bondable hydrogen atom that functions as an electron-donating group and having a π electron system. In the nonlinear optical material containing at least the compound represented by the general formula [I], electron transfer occurs rapidly when polarization occurs due to an electric field such as light, the nonlinear optical constant β is large, and a remarkable nonlinear optical effect is obtained. Indicates.

Further, according to the nonlinear optical element of the second invention, since the nonlinear optical material of the first invention is used, a second-order nonlinear optical element can be obtained, and even if the laser light with low light intensity is high in intensity, It is possible to separate the two harmonics, and it is possible to efficiently exhibit the electro-optical effect even with a small voltage change.

[Brief description of drawings]

FIG. 1 is a schematic view showing an embodiment of a non-linear optical element as an optical wavelength conversion element, and FIGS. 2 and 3 are schematic views showing other embodiments of a non-linear optical element as an optical wavelength conversion element, respectively. 4 and 5 are schematic diagrams showing an embodiment of a non-linear optical element as a phase modulation element. (1) …… Core, (2) …… Clad, (21) (31)
(41) …… optical waveguide, (22) (32) (42) …… substrate,
(33) …… Top layer, (43) …… Electrode.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Naota Uenishi 1-3-3 Shimaya, Konohana-ku, Osaka City, Osaka Prefecture Sumitomo Electric Industries, Ltd. Osaka Works (72) Inventor Norihiko Yasuda Shimaya, Konohana-ku, Osaka City, Osaka Prefecture 1-3-1 Sumitomo Electric Industries, Ltd. Osaka Works

Claims (14)

(57) [Claims] 1. A nonlinear optical material comprising at least a compound represented by the following general formula [I]. (In the formula, R ¹ and R ² are electron withdrawing atoms or electron withdrawing groups, R ³ and R ⁴ are linear or branched alkyl groups or alkoxy groups, and X is a substituent having a hydrogen bondable hydrogen atom. Indicates a group) 2. A compound represented by the general formula [I]:
R ¹ and R ² are nitro group, cyano group, cyanoalkyl group, cyanoalkoxycarbonylalkyl group, cyanoalkoxycarbonylalkenyl group, halogen atom, alkanesulfonyl group optionally having halogen atom, sulfo group, esterification Electron withdrawing selected from the group consisting of a substituted sulfo group, a carboxy group, an esterified carboxy group, an acyl group, an optionally substituted carbamoyl group, and an optionally substituted sulfamoyl group. The non-linear optical material according to claim 1 or 2, which is a polar atom or an electron-withdrawing group. 3. A compound represented by the general formula [I],
The nonlinear optical material according to claim 1, wherein R ³ and R ⁴ are linear or branched lower alkyl groups or lower alkoxy groups. 4. A compound represented by the general formula [I]:
Claim 1 wherein X is a substituent selected from the group consisting of hydroxy group, mercapto group, amino group, imino group, carboxy group, carbamoyl group, hydroxyalkyl group, hydroxyamino group and hydroxyimino group. A nonlinear optical material according to the item. 5. A compound represented by the general formula [I],
The nonlinear optical material according to claim 1 or 2, wherein R ¹ and R ² are substituted at the 2-position and 4-position of the benzene ring. 6. A compound represented by the general formula [I],
The nonlinear optical material according to claim 1 or 3, wherein R ³ and R ⁴ are substituted at the 3-position and 5-position of the benzene ring. 7. A compound represented by the general formula [I] is 3,5-
Dimethyl-2 ', 4'-dinitro-1,1'-biphenyl-
The nonlinear optical material according to claim 1, which is 4-ol. 8. A compound represented by the general formula [I] is 3,5-
Non-linear optical material according to claim 1 which is di-tert-butyl-2 ', 4'-dinitro-1,1'-biphenyl-4-ol. 9. The nonlinear optical material according to any one of claims 1, 7, and 8 which comprises a single-component crystal of a compound represented by the general formula [I]. 10. A non-linear optical element having an optical waveguide section, wherein the optical waveguide section is composed of a non-linear optical material containing at least a compound represented by the following general formula [I]. Non-linear optical element. (In the formula, R ¹ and R ² are electron withdrawing atoms or electron withdrawing groups, R ³ and R ⁴ are alkyl groups or alkoxy groups, and X is a substituent having a hydrogen atom capable of hydrogen bonding) 11. The non-linear optical element according to claim 10, wherein the non-linear optical element comprises a core made of a non-linear optical material and a clad made of a medium that covers the core and does not exhibit a non-linear optical effect. Optical element. 12. The non-linear optical element according to claim 10, wherein the non-linear optical element comprises a substrate made of a medium exhibiting no non-linear optical effect, and an optical waveguide portion made of the non-linear optical material formed on the substrate. The nonlinear optical element described. 13. A non-linear optical element comprises a substrate made of a medium exhibiting no non-linear optical effect, a layer made of a medium not exhibiting non-linear optical effect, and a non-linear optical material formed between the substrate and the layer. 11. The nonlinear optical element according to claim 10, which is composed of an optical waveguide section. 14. A non-linear optical element comprising a substrate made of a medium that does not exhibit a non-linear optical effect, an optical waveguide section made of a non-linear optical material formed on the substrate, and an electrode for applying an electric field to the optical waveguide section. Claims as constituted above
Item 10. The nonlinear optical element according to item 10.