JPH06208146A - Non-linear optical element with orientation stability - Google Patents

Abstract

(57) [Abstract] [Purpose] Providing a nonlinear optical element that is stable against changes over time [Configuration] A compound capable of exhibiting nonlinear optical characteristics represented by the following formula is contained in a sol-gel glass carrier made of silicon. And the compound is contained in the carrier such that the dipole moment is oriented in the film thickness direction. R ₁ -Ar _1- (CH = CH) n-CH = C (CN) -COOH.Z [where Z is a specific optically active amine]

Description

Detailed Description of the Invention

[0001]

The present invention relates to an optical information transmission material, short wavelength conversion in the optical recording technical field, parametric oscillation,
The present invention relates to a non-linear optical element mainly including changes in refractive index.

[0002]

2. Description of the Related Art Recently, it has been known that the nonlinear optical characteristics of organic materials are greater than those of existing inorganic compounds. The non-linear optical effect means that when a strong photoelectric field such as laser light is applied to a substance, the electric polarization response of the substance is proportional to the magnitude of the applied electric field. It shows that higher-order effects appear.

For second-order nonlinear optics, the wavelength of the incident light is 1
Second harmonic generation that converts to / 2 wavelength, parametric oscillation that converts light of one kind of wavelength into two kinds of light, conversely secondary that expresses light of one kind of wavelength from light of two kinds of wavelength There is light mixing.

Due to these characteristics, there is a high possibility that it will be used as an optical data / optical information processing, which is expected to undergo significant technological development, an optical switch used for optical communication, an optical memory, or an optical information storage element. Particularly in recent years in the optical recording field, there has been a strong demand for shortening the wavelength of reading or writing the recording code in order to perform high density recording. Although semiconductor lasers have been mainly used from the viewpoints of operability and simplicity, it is generally said that it is difficult to generate light having a wavelength shorter than 630 nm with a combination of existing semiconductor materials. From this point of view, by utilizing the second-order nonlinear optical characteristic described here, blue emission materials close to the ultraviolet region due to the generation of the second harmonic are studied in detail, and are typified by lithium niobate, KTP, and BBO. Applications in inorganic materials are being actively researched. However, inorganic materials have many practical problems such as not having a large figure of merit, low response speed, poor workability, high hygroscopicity, and low stability.

In recent years, organic compounds having high performance represented by 2-methyl-4-nitroaniline (MNA) have been developed as device materials for these inorganic materials in the form of single crystals. It is being appreciated. But organic crystals
The disadvantage is low mechanical properties and low heat resistance. Generally, the second harmonic generation ability becomes larger in a long conjugated system in which the polarization in the molecule is large and the contribution of the polarization is large. However, when the polarization is increased in this way, the stage where a crystal grows during solidification. Since the orientation of molecules is spatially stabilized so that their polarizations cancel each other and a structure of inversion symmetry is preferentially formed, a nonlinear optical effect often does not appear as an optical element. In particular, carboxylic acids, which are expected to have a large polarization effect, are known to stabilize two molecules of carboxylic acids with hydrogen bonds, as is well known. It did not become a non-linear optical activity, and was often a major obstacle for using it as a functional element utilizing a high degree of polarizability. From this point of view, various measures have been taken so that the activity of the dipole moment of one molecule remains in the solid aggregate, but it is possible to align the dipole directions by applying a high electric field. And is commonly known as corona discharge treatment. In order for this corona discharge treatment to become possible, it is necessary that the non-linear optical material is dissolved in a suitable medium and molecularly dispersed, and it can be easily treated by dissolving it in a film using a polymer as a carrier. Can be achieved.

By the way, there has been a report that a sol-gel method, which has been recently developed as a method for producing low-temperature synthetic glass, is used to produce a material in which a sol-gel glass carrier is doped with an organic substance having a nonlinear optical effect (for example, a special method). Kaihei 2-
No. 302329). According to it, the nonlinear optical organic molecules are aligned in one direction by applying an electrostatic field in the process of hydrolyzing and gelling a silicon alkoxide mixed with an organic molecule having a nonlinear optical effect. Since it is fixed in the glass matrix, a stable nonlinear optical material can be obtained.

[0007]

However, in the production method, the gelation reaction is carried out while applying an electric field at room temperature for several days, and it is said that there is a problem in productivity and economic efficiency in terms of industrial complexity due to its complexity. I have no choice. The temperature when applying the electrostatic field is as low as 50 to 80 ° C., and it is presumed that a long-time treatment is usually required.

Further, the organic molecules to be added generally do not have large solubility, and the amount of dissolution in silicon alkoxide, water and alcohol is limited, and as a nonlinear optical element,
It is difficult to get great performance. Furthermore, as a catalyst for promoting this sol-gel reaction, it is necessary to additionally attach an acid or a basic compound. For this reason, various materials added for the purpose of exhibiting the function may be condensed and modified, and the functional material may be limited.

[0009]

The present invention has been made to solve the above problems, and as a result of intensive studies, the carboxylic acid amine salt derivative (I) was added to a sol-gel glass carrier made of silicon. The non-linear optical material molecule represented by is contained in a high concentration, and the productivity is enhanced in that the polymerization proceeds due to the action of this carboxylate amine salt without adding a new catalyst, and an electric field is applied. By this, it was confirmed that the orientation of the dipole moment of the molecule was controlled and the molecule was fixed in the carrier for a long time, and the present invention was achieved.

That is, the present invention is characterized in that the dipole moment of the carboxylic acid derivative represented by the following general formula (I) having non-linear optical characteristics is oriented in the sol-gel glass carrier carrying the material. The present invention relates to an oriented nonlinear optical element and its manufacturing method.

The carboxylic acid amine salt derivative having nonlinear optical characteristics described here is represented by the following general formula (I).

[0012]

[Chemical formula 3] R₁-Ar₁-(CH = CH) n-CH = C (CN) -COOH.Z (I) [wherein n represents 0, 1 or 2] Ar₁Is the carbon number
It represents an aromatic group of 5 to 14. R₁-Is R₂R₃N-
Amino group represented, and hydrogen halide salt thereof, R_Four
An ether group represented by -O-, R_FiveJ represented by -S-
Ether group, cyano group, -COOR₆Or-OCO
R₇An ester group represented by —CONR₈R₉, -NR
_TenCOR₁₁An amide group represented by₁₂Carbonization represented by
Hydrogen group (R ₂-R₁₂Are the same or different and have 1 carbon
~ Monovalent hydrocarbon group of 8 or represents a hydrogen atom)
It is the functional group of choice. Z is optically active 1-phenyl
Ethylamine, 1-α-naphthylethylamine, 1-f
Phenyl-2-methylethylamine, 1-phenyl-2-
Aminopropane, 2-Amino-1-butanol, 1-A
Mino-2-propanol, 2-amino-1-propanol
2-amino-1- (p-nitrophenyl) -1,3
-Propanediol, 2-Dimethylamino-1-phenyl
Ru-1-benzil-1-propanol, 1- (N, N
-Dimethylamino) -In 1-phenylpropylamine
It is one kind or a mixture of two or more kinds selected from. ]

Regarding the synthesis of carboxylic acid derivatives among such materials, for example, as shown in JP-A-1-245230 (published on September 29, 1991), a reaction between an aromatic aldehyde and an active methylene compound is carried out. The α-cyanoacrylic acid compound obtained in 1. is applicable. Since the carboxylic acid derivative has a symmetrically arranged structure during crystallization due to the hydrogen bond of the acid, the carboxylic acid derivative generally does not exhibit the second-order nonlinear optical characteristics. Therefore, the secondary nonlinear optical characteristics cannot be expected by simply dissolving and molecularly dispersing this acid in the sol-gel glass support described below. For this reason, the conventional method is devised to apply a high electric field represented by corona poling to forcibly control the orientation.

The glass synthesis method called the sol-gel method, which has been developed in recent years, is different from the conventional production method requiring a high temperature of several thousand and several hundred degrees, and the silicon alkoxide is reacted with alcohol and water in the presence of a catalyst at room temperature or higher to hydrolyze. It is a low-temperature synthesis method that gives glass by polycondensation via

By using this method, an organic compound having poor heat resistance can be added to the silicon alkoxide solution before the hydrolysis reaction in advance, so that it can be uniformly dispersed in the glass.

In the present invention, the hydrolysis reaction of silicon alkoxide is carried out according to a general sol-gel method. The feature of the present invention is that it is not necessary to add any catalyst at this time. From various analyzes, it is considered that the amine component of the compound carboxylic acid amine salt (I) partially dissociates and catalyzes as a free amine.

General Formula of the Invention

[0018]

Embedded image As the silicon alkoxide represented by Si (OR ⁰ ) ₄ (II), R ⁰ is a saturated hydrocarbon group having 1 to 4 carbon atoms, and tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane,
It is a kind selected from tetrabutoxysilane. A silicon alkoxide having a hydrocarbon group of R ⁰ having a large number of carbon atoms generally has a low hydrolysis rate, and when R ^{0 has} a carbon number of 5 or more, productivity is low and not practical. The alcohol is used as a solvent in the sol-gel method, and examples thereof include methyl alcohol, ethyl alcohol, propyl alcohol and butyl alcohol.

The addition ratio of the above alcohol and water to 1 mol of silicon alkoxide is not particularly limited,
Alcohol is 0.2 to 20 mol and water is 1 to 10 mol.

By the way, the above chemical formula (I) or (I
The organic compound represented by I) can be easily dissolved by using a highly polar solvent. In order to exert the performance as a non-linear optical element, it is desirable that the organic dye compound having a large non-linear effect is present at a concentration as high as possible. Silicon alkoxide, which is a starting material in the sol-gel method, is not very polar and it is difficult to dissolve the compound at a high concentration.

On the other hand, in the sol-gel method, when the hydrolysis reaction proceeds and the condensation polymerization further progresses to produce a glass body, the hydroalcohol existing in the system evaporates. Since the concentration is different and stress is generated,
Cracks, fractures, and fragmentation may occur. When manufacturing a glass without such defects, it is effective to add a polar solvent having a boiling point higher than that of water. Since the polar solvent having a surface tension smaller than that of water is present in the reaction system even after the evaporation of water, the tensile stress generated in the surface layer of the produced glass body is weakened and a glass body having no defects can be obtained. That is, by adding the polar solvent, it is very effective to dissolve the organic dye compound in the silicon alkoxide solution at a high concentration and to manufacture a non-linear optical element having no defect.

As the polar solvent used in the present invention, it is sufficient that an organic dye compound is dissolved in a high concentration and is compatible with silcon alkoxide, alcohol and water, and a glass body free from defects is obtained. , N-dimethylformamide, N, N-dimethylacetamide, and cyclohexanone, or a mixture of two or more thereof.

The addition amount is not particularly limited, but is 0.1 to 10 mol, preferably 0.5 to 5 mol, per 1 mol of silicon alkoxide. If the amount is less than 0.1 mol, the organic compound cannot be sufficiently added and defects are likely to occur in the glass body. On the other hand, if it exceeds 10 moles, the production rate of the glass body will be low and the productivity will be low.

Generally, when water and a basic catalyst are added to a solution obtained by adding an alcohol, a polar solvent and an organic compound to a silicon alkoxide, hydrolysis and polycondensation reaction occur. At that time, the reaction is accelerated by heating,
Alcohol, water, and a polar solvent are evaporated and removed from the system in this order, and a transparent glass body can be efficiently obtained with high productivity. The heating temperature depends on the melting point or decomposition temperature of the added organic compound, but it is desirable that the heating temperature is near the boiling point of the polar solvent used and near or below the melting point of the organic compound, and is selected in the range of 100 ° C to 200 ° C. Be done. When the temperature is lower than that, a large amount of the polar solvent remains on the glass carrier. On the other hand, when the temperature exceeds 200 ° C., a part of the organic dye compound may be sublimated, decomposed or metamorphosed, which is not preferable. The polymerization reaction proceeds without adding a catalyst only by this heat treatment, but in this case, in the present invention, the amine component of the carboxylic acid amine salt (I) has a stronger basicity than the contribution of the carboxylic acid as an acid. It is considered to indicate.

By aligning organic molecules by corona discharge,
As an example in which the center of symmetry is broken to generate the second harmonic, the polymer is used as a carrier and the Desperse Red-1 (Di
An example in which an azo dye called sperseRed 1) is dispersed,
Alternatively, there is an example in which p-nitroaniline is dispersed.
They are, for example, the magazine Optronics (1990),
No. 3, p. 128, Iwao Senoo, et al., "Polymer Nonlinear Optical Material," or the magazine O PLUS E (1990).
It is described in detail in "Application of Polymers to Optical Waveguides" by Keisuke Sasaki described in the December issue, page 129.

As a method of breaking the center of symmetry as described above, there is a method of preparing a chiral derivative in advance. As in the present method, the optically active amine salt alone has a spatial arrangement of carboxylic acid and a direction in which its dipoles are aligned. To array. In addition to this effect, it is expected that there will be a corona discharge orientation effect, which will be described later, and the regularity will be remarkably improved.

In carrying out the above method, it is preferable to apply a DC electric field in order to align the dipole moment directions of the nonlinear optically active compound inside the glass body. As a method of applying this high electric field, various methods are conceivable as long as the polymer carrier is effectively charged, and various methods are conceivable. However, the method using corona discharge can be easily achieved. Corona discharge refers to corona discharge by applying a high voltage, for example, 1 kV or more, preferably 5 to 12 kV, by the DC power supply 11 between the flat plate electrode 15 and the needle electrode 12 as shown in FIG. To generate the glass body 13
Is to be charged.

As a phenomenon at this time, molecules in the air are ionized, and the ions fly toward the plate electrode, and as a result, a large number of ions are accumulated in the glass carrier, and the upper electrode and the glass carrier surface are The discharge will continue until the potentials become equal. During this time, the carrier surface 13 and the plate electrode 15
An applied potential difference is generated between the two, and the organic compound of the nonlinear optical material in the carrier retains its dipole moment in parallel with the electric field. That is, the orientation is uniform in the film thickness direction of the glass carrier.

As described herein, an attempt to use a polymer as a carrier is already known, but at this time, although the orientation of the organic molecules is uniform, the free space volume of the polymer changes with time, and as a result, the organic molecules become It is recognized that the orientation disappears successively in that space, and as a result, the nonlinearity decreases.

On the other hand, the sol-gel glass described in the present invention is
The behavior corresponding to the change of the free volume space of the polymer material is suppressed. This is because the formation of sol glass has a complete three-dimensional cross-linking of the polycondensation reaction as a basic structure, and the change to sol-gel glass further accelerates this cross-linking process, so that the microscopic space is almost fixed. It is thought to be because of it. Stabilization to such morphological changes retains the morphology of the organic molecules that are dispersed and oriented in the glass, so that the asymmetry is maintained, and as a result, the change in nonlinear characteristics over time is significantly controlled. The present invention has been reached.

In this corona discharge, one pole is
It is not always necessary to have a needle shape, and a linear shape is also suitable for the purpose shown here, and in some cases it is more desirable because an even electric field is effectively applied to the glass carrier.

The orientation of the molecules can be confirmed by observing the second harmonic by changing the polarization direction of the incident light while rotating the corona-discharged glass carrier. The spectrum can be confirmed by measuring the polarization direction dependence.

The present invention will be described in detail below with reference to examples.

[0034]

Example 1 As an organic dye molecule, 0.21 g of 5- (4-dimethylaminophenyl) -2-cyanopentagenonic acid and 1-phenylethylamine salt was added together with 2.83 g of N, N-dimethylformamide (DMF) to give tetra. The mixture was added to a mixed liquid of 1.74 g of ethoxysilane and 4.8 g of methanol, stirred and dissolved. After adding 1.0 g of water to this and making it react overnight, this was formed into a film by the spin coater of 2000 rpm for 1 minute, and it created on the glass substrate. After leaving this glass substrate at room temperature for 10 minutes, it was placed on a flat plate electrode as shown in FIG. 1 and was placed 8 mm below the linear electrode on one side and heated to 150 ° C. while applying an electric field of 10 kV. It was applied for 60 minutes by corona discharge. The obtained sample is Nd-Y
When the fundamental light of the AG laser with a wavelength of 1.06 μ was incident, a green emission of 0.53 μ, which was the second harmonic, was observed.

[0035]

[Comparative Example 1] Desperse Red 1 as an organic dye molecule
The same operation as in Example 1 (catalyst-free system) was carried out using, but no film could be obtained on the glass substrate.

[0036]

Examples 2 to 6 The same experiment as in Example 1 was conducted using the following compounds, and the generation of the second harmonic was observed in each case.

[0037]

[Table 1]

[Brief description of drawings]

FIG. 1 shows an outline of corona discharge.

[Explanation of symbols]

 11 high-voltage power supply 12 wire 13 carrier 14 substrate 15 plate electrode

Claims (4)

[Claims] 1. A compound capable of exhibiting non-linear optical properties,
Be contained in a sol-gel glass carrier made of silicon.
And the compound has a dipole moment in the carrier.
Is contained so that the direction of the film is oriented in the film thickness direction.
In the non-linear optical element, the compound is represented by the following formula (I):₁-Ar₁-(CH = CH) n-CH = C (CN) -COOH.Z (I) [wherein n represents 0, 1 or 2] Ar₁Is the carbon number
It represents an aromatic group of 5 to 14. R₁-Is R₂R₃N-
Amino group represented, and hydrogen halide salt thereof, R_Four
An ether group represented by -O-, R_FiveJ represented by -S-
Ether group, cyano group, -COOR₆Or-OCO
R₇An ester group represented by —CONR₈R₉, -NR
_TenCOR₁₁An amide group represented by₁₂Carbonization represented by
Hydrogen group (R ₂-R₁₂Are the same or different and have 1 carbon
~ Monovalent hydrocarbon group of 8 or represents a hydrogen atom)
It is the functional group of choice. Z is optically active 1-phenyl
Ethylamine, 1-α-naphthylethylamine, 1-f
Phenyl-2-methylethylamine, 1-phenyl-2-
Aminopropane, 2-Amino-1-butanol, 1-A
Mino-2-propanol, 2-amino-1-propanol
2-amino-1- (p-nitrophenyl) -1,3
-Propanediol, 2-Dimethylamino-1-phenyl
Ru-1-benzil-1-propanol, 1- (N, N
-Dimethylamino) -In 1-phenylpropylamine
It is one kind or a mixture of two or more kinds selected from. ]
Characterized by being a carboxylic acid amine salt derivative represented by
And a nonlinear optical element. 2. The sol-gel glass made of silicon,
A silicon alkoxide represented by the following general formula (II): Si (OR ⁰ ) ₄ (II) [wherein R ⁰ represents a hydrocarbon group having 1 to 4 carbon atoms] is used as a starting material. The non-linear optical element according to claim 1, wherein the non-linear optical element is present. 3. A polar solvent having a boiling point of 100 ° C. or more and 200 ° C. or less and a compound represented by the general formula (I) are present in the alcohol solution of silicon alkoxide, and water is added thereto, and then 100 ° C. or more. A method for producing a non-linear optical element, characterized in that a voltage of 0.5 kV or more and 40 kV or less is applied at a temperature of 200 ° C. or less to corona-poling to orient the compound and at the same time polymerize the silicon alkoxide. 4. The method for producing a nonlinear optical element according to claim 4, wherein the polar solvent is one kind or a mixture of two or more kinds selected from N, N-dimethylformamide, N, N-dimethylacetamide and cyclohexanone. .