JP2999673B2 - Method for producing electro-optical material and apparatus for producing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing an electro-optical material exhibiting an electro-optical effect, which is a constituent material of an optical signal control device and the like, and an apparatus for producing the same.

[0002]

2. Description of the Related Art Conventionally, an electro-optic material having a Pockels effect (hereinafter referred to as an electro-optic effect), which is a second-order nonlinear optical effect, is manufactured by the following procedures (1) to (7).

(1) Crystals of molecules having hyperpolarizability (hereinafter referred to as non-linear molecules) or polymers containing non-linear molecules dispersed or bonded, amorphous or solutions containing non-linear molecules intended for use below the freezing point (Hereinafter referred to as an electro-optic material).

(2) The volatile components in the electro-optic material are removed by drying (however, this process is excluded in the case of a solution).

(3) The melting point or glass transition temperature of the electro-optical material or a temperature higher than those temperatures.

(4) A DC voltage is applied to the electro-optic material to orient the nonlinear molecules in the electric field.

(5) While a DC voltage is applied to the electro-optic material, the temperature of the electro-optic material is lowered below its melting point or glass transition temperature to fix the oriented nonlinear molecules.

(6) Dissolving the DC voltage applied to the electro-optical material.

(7) An AC voltage is applied to the obtained electro-optic material, and the dependency of the birefringence of the electro-optic material on the AC voltage is examined to measure an electro-optic constant which is a second-order nonlinear optical constant.

In the above (4), the following (i),
There is also a method in which the nonlinear molecule is oriented while observing the orientation state or motion state of the nonlinear molecule by the method (ii).

(I) Irradiating the electro-optical material with laser light, measuring the intensity of the second harmonic, and observing the orientation state of the nonlinear molecule (Levenson et al., Nonlinear Optics, No. 4
Volume, p. 233 (1993)).

(Ii) Simultaneously applying a DC voltage and an AC voltage to the polymer film of the electro-optical material to induce periodic alignment motion in the nonlinear molecules and observe the polarization state of the laser light passing through the polymer film. Then, the mobility of the nonlinear molecule is observed (Aramaki et al., Proceedings of the 54th JSAP, page 1094 (1993)).

[0013]

In the conventional method of manufacturing an electro-optic material, the process must be performed after a process of heating the electro-optic material, orienting the electric field of the nonlinear molecule, and fixing the nonlinear molecule by cooling the electro-optic material. In addition, the electro-optical characteristics cannot be examined. That is, since the electro-optical characteristics depend on manufacturing conditions such as electric field orientation temperature, applied voltage, and voltage application time, to manufacture an electro-optical material having a larger electro-optical constant, the maximum electro-optical constant is determined by trial and error. It is necessary to find out the optimal production conditions that allow the expression, and then to set the conditions to produce the electro-optical material.

Also, when manufacturing an electro-optical material having a certain specific value of the electro-optical constant, a specific manufacturing condition capable of expressing the electro-optical constant by trial and error has been found.
Thereafter, it is necessary to produce an electro-optic material under the conditions.

In the methods (i) and (ii), information on the orientation or mobility of nonlinear molecules can be obtained, but the magnitude of the electro-optic effect of the electro-optic material is not necessarily given. Furthermore, the second harmonic generation is the same second-order nonlinear effect as the electro-optic effect, but if the material itself absorbs the second harmonic, the magnitude of the second harmonic is not necessarily the magnitude of the electro-optic effect. Was not reflected.

It is an object of the present invention to obtain a larger electro-optical constant while monitoring the electro-optical constant or the magnitude of the electro-optical effect, or to obtain an electro-optical constant having a specific value. An object of the present invention is to provide a method for manufacturing an electro-optical material to be manufactured by controlling manufacturing conditions so as to obtain it.

Another object of the present invention is to provide an apparatus for manufacturing the above-mentioned electro-optical material.

[0018]

The gist of the present invention to achieve the above object is as follows.

[1] In a method for producing an electro-optic material having a Pockels effect in which an electric field is applied to orient nonlinear molecules, the electric field orientation temperature is monitored while monitoring the magnitude of the electro-optic constant of the electro-optic material during the electric field orientation. , An applied voltage and a voltage application time are controlled.

[2] The method for producing the electro-optic material, wherein the electro-optic material is a material selected from a crystal of a nonlinear molecule, an organic polymer in which the nonlinear molecule is dispersed or bonded, an amorphous material, or a solution containing the nonlinear molecule. It is in.

[3] In the method for producing an electro-optical material for applying an electric field to orient nonlinear molecules, the electric field may be:
DC voltage and a high frequency at which the molecular orientation motion of the nonlinear molecule cannot follow, and an AC voltage having an amplitude smaller than the DC voltage are simultaneously applied, and the dependency of the birefringence of the electro-optical material on the AC voltage is applied. While monitoring at least one of the electric field orientation temperature, the applied voltage, and the voltage application time.

[4] The dependence of the birefringence of the electro-optical material on the alternating voltage is monitored, and at least one of the electric field orientation temperature, the applied voltage, and the voltage application time is determined from the obtained electro-optical constant of the electro-optical material. There is a method of manufacturing an electro-optic material for controlling one.

[5] An AC voltage is applied at the same time as a DC voltage for orienting the non-linear molecules to exhibit the electro-optic effect, and the polarization state of the incident light, which changes due to the electro-optic effect caused by the AC voltage, is monitored. , An applied voltage and a voltage application time are controlled.

[6] An electric field applying means for applying a direct current and an alternating voltage to the electro-optical material to orient the nonlinear molecules in an electric field, a heating means for the electro-optical material, and a single polarized component in the electro-optical material. Light irradiation means for irradiating light,
Light detecting means for detecting the transmitted light of the electro-optical material that changes by applying an electric field, and control means for controlling at least one of the electric field intensity of the electric field applying means, the electric field application time, and the heating temperature of the electro-optical material are provided. It is in the electro-optical material manufacturing equipment.

[7] The light detecting means detects a polarizing element (for example, a Wollaston prism) that divides the transmitted light of the electro-optical material into two orthogonal polarized light components, and detects the respective polarized light components separated by the polarizing element. A control device that includes a photodetector (for example, a photodiode) and controls at least one of the electric field intensity of the electric field applying unit, the electric field application time, and the heating temperature of the electro-optical material based on the intensity difference between the two polarized lights. The manufacturing apparatus for an electro-optical material having:

As the electro-optic material of the present invention, an amorphous material such as a polymer in which nonlinear molecules are dispersed or bonded, a glass in which nonlinear molecules are dispersed or bonded, or
There is a solution containing a nonlinear molecule intended for use at a temperature lower than its melting point. A method of monitoring the electro-optic constant of the electro-optic material during the electric field orientation of the nonlinear molecules will be described.

A DC voltage and an AC voltage having a smaller amplitude are simultaneously applied to the electro-optical material. Non-linear molecules in a material have the property of orienting their dipoles in the direction of a DC electric field with respect to a DC voltage. On the other hand, for an AC voltage, the nonlinear molecules exhibit an orientation motion according to the frequency of the AC electric field, but if the frequency of the AC is increased to such an extent that the orientation motion of the nonlinear molecule cannot follow the AC electric field,
The orientation direction of the nonlinear molecule does not depend on the AC electric field.

In a polymer or an amorphous state, when an AC voltage of 100 kHz or more is applied near the glass transition temperature, the nonlinear molecules do not perform the alignment motion induced by the AC electric field. The change in the birefringence of the electro-optic material due to the alternating electric field at this time is due to the electro-optic effect of the electro-optic material.

The dependence of the change in the birefringence on the strength of the AC electric field of the electro-optic material is examined using light in a single polarization state as monitor light. When the monitor light is transmitted through the electro-optic material, the polarization state of the transmitted light changes reflecting the birefringence of the electro-optic material. The electro-optic constant can be obtained from the polarization state of the monitor light transmitted through the electro-optic material, that is, the dependency of the birefringence of the electro-optic material on the applied AC voltage.

Since the birefringence of the electro-optic material caused by the electro-optic effect is reflected in the monitor light, the monitor light can be used as signal transmission means. That is, by simultaneously applying a DC voltage for exhibiting an electro-optic effect for orienting nonlinear molecules and an AC voltage having a signal property, the signal property of the AC voltage is reflected on the polarization state of the light transmitted through the material.

The DC applied electric field to the electro-optical material is 10 to 1
The applied voltage is 50 V / μm, the AC applied electric field is 1 to 5 V / μm, and the frequency of the AC voltage is 100 kHz or more. The application of the DC voltage and the AC voltage to the electro-optical material may be performed simultaneously using the same electrode pair, or may be performed by providing a DC electrode pair and an AC electrode pair, respectively. In the latter case, the application directions of the DC and AC electric fields may be parallel or orthogonal,
In places where the monitor light passes, both the direct current and the alternating current require the above-mentioned electric field strength.

As a method for detecting a change in the polarization state due to a change in the birefringence of the electro-optic material due to the application of an AC voltage,
For example, there are the following (1) to (6).

(1) From the monitor light transmitted through the electro-optical material, only a specific polarized component is extracted using a polarizer and detected by a photodetector such as a photodiode. When the polarization state of the monitor light changes, the intensity of light passing through the polarizer changes. Therefore, the polarization state can be determined by monitoring the output from the photodetector.

(2) The monitor light transmitted through the electro-optical material is separated into two orthogonal polarization components using a polarizer such as a Wollaston prism. When the polarization state of the monitor light changes, one polarization component increases and the other polarization component decreases. Therefore, the intensity of these two polarizations is measured using a photodetector, and the polarization state is known from the difference.

(3) The monitor light transmitted through the electro-optical material is extracted only with a specific polarization component using a polarizer.
A second harmonic of this light or a higher harmonic thereof is generated and monitored. When the polarization state of the monitor light changes, the intensity of the higher-order harmonic also changes. In addition, since the intensity of the higher-order harmonic reflects the intensity change of the fundamental wave more sharply, by monitoring the intensity of the higher-order harmonic, the polarization state of the monitor light can be understood more sharply.

(4) From the monitor light transmitted through the electro-optical material, only a specific polarization component is extracted using a polarizer,
The light is transmitted through a medium excited by another light and amplified. The polarization state of the monitor light can be determined from the intensity of the amplified light.

(5) A sum frequency or a difference frequency is generated between the monitor light transmitted through the electro-optic material and another light having a single polarization state, and this is detected by a photodetector. When the polarization state of the monitor light changes, the intensity of the sum frequency or the difference frequency changes, so that the polarization state can be known.

(6) When the electro-optic material absorbs the monitor light, the change in the birefringence caused by the electro-optic effect is accompanied by a change in the extinction coefficient. The electro-optic constant can be obtained by examining the change in the extinction coefficient of the electro-optic material as monitor light using the absorption light of the electro-optic material (in any region, visible or infrared). The transmission intensity of the monitor light is monitored by a photodetector, and its dependence on the applied AC voltage is examined to determine the electro-optic constant. Further, by generating a higher harmonic of the transmitted light and monitoring the intensity, a change in the intensity of the monitor light can be more sharply measured.

In the above, it is not necessary to always apply the AC voltage. An AC voltage may be applied only when measuring the electro-optic constant of the electro-optic material. The distance between the electrodes is preferably 0.1 to 100 μm.

From the above, the electro-optic constant of the electro-optic material,
Alternatively, while measuring the magnitude of the electro-optic effect, the conditions for producing the electro-optic material such as applied voltage, voltage application time, material temperature, material hydrogen ion concentration, material pressure, mixture ratio of a plurality of compounds, light Irradiation is adjusted to maximize the electro-optic effect of the material to orient the nonlinear molecules.

When it is necessary to set the electro-optic constant of the material to a specific value, the above conditions are adjusted in the same manner.

In general, when a non-linear molecule is dispersed or bonded to an organic polymer, a DC applied voltage, a voltage applied time,
The temperature of the material is the manufacturing condition. In order to set the electro-optic constant to a specific value, it is effective to adjust the DC applied voltage and control the degree of orientation of the nonlinear molecule.

Also, a molecule such as 4-azidophenylcarboxyethyl methacrylate which reacts by absorbing light to exhibit non-linear characteristics (Hayashi et al., Macromolecules, Vol. 25, pp. 5094 (1992)) When is used as a non-linear molecule, light is irradiated while monitoring the electro-optic constant, and the light irradiation is stopped when the electro-optic effect no longer increases. Excessive light irradiation may cause decomposition of nonlinear molecules, leading to a decrease in nonlinear characteristics.

When the concentration of hydrogen ions in the material or the mixing ratio of a plurality of compounds affects the magnitude of the electro-optical effect, these setting conditions are changed so that the electro-optical constant becomes maximum or a specific value. Let it.

While the voltage is applied, the temperature of the electro-optical material is lowered below its melting point or glass transition temperature to fix the orientation of the nonlinear molecule, and then the applied direct-current voltage is released to obtain the electro-optical material of the present invention. Material can be obtained.

[0046]

According to the conventional method for producing an electro-optical material, heating of the material,
Electric field orientation of nonlinear molecules, fixation of nonlinear molecules by cooling,
Since the electro-optical characteristics can be evaluated only after the process described above, the electro-optical material having the optimal conditions for exhibiting the maximum electro-optical effect, or having a specific value of the electro-optical constant . <br/> A lot of trial and error was required before finding the conditions for producing.

According to the present invention, since the production conditions are controlled while monitoring the electro-optic constant of the nonlinear molecule, the optimum conditions can be easily found, and it is extremely easy to provide an electro-optic material having an arbitrary electro-optic constant. It became.

[0048]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to embodiments.

As shown in FIG. 2, a reflective dielectric multilayer film 3 is formed on a substrate (substrate (substrate having a mirror-like surface and an electric resistance of 10 times or more that of the electro-optical material)), and a voltage application voltage is applied thereon. , Which are covered with an electro-optic material 2.

This is mounted in a temperature controller 10 shown in the schematic configuration diagram of FIG. 1, and a laser beam from a laser light source 5 is applied to the electro-optic material 2 through a polarizer 6, a mirror 7, and a lens 9. I do.

The electro-optical material 2 has a control power source 1
1 is configured to be able to apply DC and AC voltages between the electrodes 1. The laser reflected light of the electro-optic material 2 that changes according to the applied electric field is detected by the photodiode 16 via the mirror 8, the Soleil-Babinet compensator 14, and the polarizer 15. The detection signal enters the lock-in amplifier 17 from the signal input terminal 18 and lock-in is detected by the reference signal 13 having the same cycle as the AC voltage. Since the magnitude of the detection signal reflects the magnitude of the electro-optic effect, the intensity of the electric field applied between the electrodes 1 is controlled by the control power supply 11 while observing the magnitude.

FIG. 3 is a schematic structural view of a detecting section using a Wollaston prism 21 as detecting means.

Here, as the target electro-optical material 2,
Disperse Red 1 0.2, a dye that is a nonlinear molecule
g and 2 g of polymethyl methacrylate are dissolved in 20 ml of chloroform and applied by spin coating on a substrate 4 on which the electrode 1 and the reflective dielectric multilayer film 3 are formed as shown in FIG. A membrane was obtained. The electro-optic material 2
Had a glass transition temperature (Tg) of about 95 ° C.

This is referred to as the temperature controller 10 in FIG.
Is set to 50 ° C., and 50 V / μm is applied to the electro-optic material 2.
Is applied, the non-linear molecules in the electro-optic material 2 are oriented in the direction of the electric field. In addition, the frequency 10
0 kHz AC voltage (5 V / μ for electro-optical material)
m) was superimposed and applied to the electro-optic material 2.

The electro-optic effect of the electro-optic material 2 is detected as follows. The laser light source 5 and the polarizer 6 are adjusted to irradiate a laser beam having a wavelength of 632.8 nm in which the polarization direction of the incident light is at 45 degrees with respect to the orientation axis of the nonlinear molecule (the direction of the DC electric field). The laser light reflected by the reflective dielectric multilayer film 3 changes its polarization characteristics due to the birefringence of the electro-optic material 2, and only a specific polarization component is extracted by the polarizer 15.

When the birefringence of the electro-optic material 2 changes,
Since the intensity of the light passing through the polarizer 15 changes, this is detected by the photodiode 16 and the electro-optic material 2 is detected.
The lock-in is detected by the reference signal 13 of the AC applied voltage to obtain the electro-optic constant or the magnitude of the electro-optic effect of the electro-optic material 2.

Further, by using the light detecting means as shown in FIG. 3, the magnitude of the electro-optic effect of the electro-optic material 2 can be reduced.
Higher sensitivity can be detected. In this light detecting means, the transmission monitor light of the electro-optical material 2 is divided into two orthogonal polarization components by the Wollaston prism 21 and detected by the photodiodes 22 and 23, respectively.

When the birefringence of the electro-optic material 2 changes,
One of the separated polarization components increases and the other decreases. Therefore, the lock-in detection of the difference between the outputs from the two photodiodes 22 and 23 using the reference signal of the AC applied voltage to the electro-optic material 2 allows the electro-optic constant of the electro-optic material 2 to be obtained. in this case,
By monitoring the difference between the outputs from the two photodiodes 22 and 23, it is possible to detect a change that is twice the amount of change in light. In addition, noise components common to the two photodiodes 22 and 23, such as light source fluctuation, can be canceled by taking the difference between them. Can be detected more sharply.

As described above, while monitoring the magnitude of the electro-optic effect, the temperature, the DC applied voltage, and the voltage application time of the electro-optic material 2 when the electric field is oriented are adjusted.

The temperature controller 10 raises the temperature of the electro-optic material 2 from 50 ° C. at a rate of 1 ° C./min. (1) Whether the electro-optic constant increases as the temperature rises
Otherwise, if it does not change, the temperature is kept rising.

(2) If the electro-optic constant decreases with an increase in temperature, the temperature is returned to the temperature immediately before the decrease starts, and the temperature is fixed.

Next, the DC applied voltage is increased from 50 V / μm. The magnitude of the electric field at which the electro-optic material 2 causes dielectric breakdown is checked in advance, and the DC applied voltage is increased while monitoring the magnitude of the electro-optic effect with an electric field lower than the electric field.

(3) If the electro-optic constant increases or does not change with the voltage rise, the voltage rise is continued.

(4) When the electro-optic constant decreases with an increase in the voltage, the voltage is returned to the voltage immediately before the decrease and fixed.

After setting the temperature and the applied voltage as described above, the temperature is changed within the above set temperature range of -20 ° C. to + 20 ° C. to set the temperature at which the electro-optical effect is maximized.
In the same manner, the process of setting the DC applied voltage is repeated a plurality of times to search for a point where the electro-optical effect is maximized.

Next, the electric field orientation time is set while monitoring the electro-optic constant. The electric field orientation is performed under the above-mentioned set conditions, and the time-dependent change of the electro-optic effect is observed. When the magnitude does not increase, the temperature is lowered to fix the nonlinear molecules.

According to the above method, the electro-optic constant is 4p
An electro-optic material comprising m / V disperse red 1 dispersed polymethyl methacrylate was prepared.

[0068]

According to the present invention, the electro-optical characteristics of the electro-optical material can be produced while monitoring the state of the electric field orientation of the non-linear molecules, and the electro-optical material capable of exhibiting the maximum electro-optical constant can be obtained. .

Further, since the manufacturing conditions can be adjusted while monitoring the electro-optical constant, an electro-optical material having a specific electro-optical constant can be manufactured.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an apparatus for manufacturing an electro-optical material according to the present invention.

FIG. 2 is a schematic diagram of an electrode unit of FIG.

FIG. 3 is a schematic configuration diagram of a light detection unit that monitors a minute change in a birefringence of an electro-optic material.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Electrode for voltage application, 2 ... Electro-optic material, 3 ... Reflection dielectric multilayer film, 4 ... Substrate, 5 ... Laser light source, 6 ... Polarizer, 7,8 ... Mirror, 9 ... Lens, 10 ... Temperature Controller, 11: Control power supply, 12: Output terminal, 13
... Reference signal output with the same cycle as the AC voltage, 14 Soleil-Babinet compensator, 15 Polarizer, 16, 22, 23 Photodiode, 17, 27 Lock-in amplifier, 18 Signal input terminal, 19 Reference signal Input terminal, 20: photodetector, 21: Wollaston prism, 24, 25: signal input terminal, 26: reference signal input terminal.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G02F 1/35 G02F 1/03

Claims (8)

(57) [Claims] 1. A method for producing an electro-optical material having a Pockels effect in which an electric field is applied to orient nonlinear molecules,
A method for producing an electro-optic material, wherein at least one of an electric field orientation temperature, an applied voltage, and a voltage application time is controlled while monitoring the magnitude of an electro-optic constant of the electro-optic material during the electric field orientation. 2. The electro-optic material according to claim 1, wherein the electro-optic material is a material selected from a crystal of nonlinear molecules, an organic polymer in which nonlinear molecules are dispersed or bonded, amorphous, or a solution containing nonlinear molecules. Manufacturing method of optical materials. 3. A method for producing an electro-optical material having a Pockels effect in which an electric field is applied to orient nonlinear molecules,
As the electric field, a DC voltage and a high frequency at which the molecular orientation motion of the nonlinear molecules cannot follow, and an AC voltage having an amplitude smaller than the DC voltage are simultaneously applied, and the AC of the birefringence of the electro-optic material is applied. A method for producing an electro-optical material, wherein at least one of an electric field alignment temperature, an applied voltage, and a voltage application time is controlled while monitoring the dependence on a voltage. 4. A method for producing an electro-optical material having a Pockels effect in which an electric field is applied to orient nonlinear molecules,
As the electric field, a DC voltage and a high frequency at which the molecular orientation motion of the nonlinear molecules cannot follow, and an AC voltage having an amplitude smaller than the DC voltage are simultaneously applied, and the AC of the birefringence of the electro-optic material is applied. Monitor the dependence on voltage,
From electro-optic coefficient of the electro-optical material obtained by this, electrostatic
At least the field orientation temperature, applied voltage and voltage applied time
A method for producing an electro-optical material, characterized by controlling one . 5. A method for producing an electro-optical material having a Pockels effect of orienting a nonlinear molecule by applying an electric field,
An AC voltage is applied at the same time as a DC voltage for orienting the non-linear molecules to exhibit the electro-optical effect, and the polarization state of incident light that changes due to the electro-optical effect caused by the AC voltage is monitored.
A method for producing an electro-optical material, wherein at least one of an electric field orientation temperature, an applied voltage, and a voltage application time is controlled. 6. A method for producing an electro-optic material having a Pockels effect in which an electric field is applied to orient nonlinear molecules,
The electro-optic material is made of a material that exhibits non-linear characteristics by absorbing light, irradiates light while monitoring the electro-optic constant, and stops irradiation when the electro-optic constant reaches a predetermined value. A method for producing an electro-optical material, characterized by controlling. 7. An electric field applying means for applying DC and AC voltages to an electro-optical material having a Pockels effect to orient a nonlinear molecule in an electric field, a heating means for the electro-optical material,
Light irradiating means for irradiating the electro-optical material with light having a single polarization component; light detecting means for detecting light transmitted through the electro-optical material which changes by applying the electric field; An apparatus for manufacturing an electro-optical material, comprising: control means for controlling at least one of an electric field application time and a heating temperature of the electro-optical material. 8. The apparatus according to claim 1, wherein said light detecting means includes a polarizing element for dividing the transmitted light of said electro-optical material into two orthogonal polarized light components, and a photodetector for detecting each polarized light component separated by said polarizing element. 8. The electro-optic material according to claim 7, further comprising a control device for controlling at least one of an electric field intensity of the electric field application means, an electric field application time, and a heating temperature of the electro-optic material based on a difference between the two polarization intensities. Manufacturing equipment.