JP2716070B2 - Method for producing nonlinear optical amorphous material - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an improvement in a method for producing an amorphous material doped with organic material molecules having a nonlinear optical effect.

2. Description of the Related Art It is well known that crystals having an asymmetric center of a certain organic or inorganic compound exhibit second-order nonlinear optical characteristics. Such crystals have a crystallographic space group lacking the center of inversion symmetry. Such second-order nonlinear optical effects include second harmonic generation that emits light at twice the frequency of light incident on the crystal. Such an effect is useful when there is no high-quality laser that oscillates at a short wavelength.

(Problems to be Solved by the Invention) Potassium dihydrogen orthophosphate, ammonium dihydrogen orthophosphate, and the like are known as crystals exhibiting the second-order nonlinear optical effect. These crystals are difficult to make,
It is expensive and brittle.

In organic crystals, 2-methyl-4-nitroaniline, 3-acetamido-4-dimethylaminonitrobenzene, and the like are known to have large nonlinear optical constants, but they have problems in mechanical strength. Are difficult to put into practical use.

Therefore, a non-linear optical material having a large non-linear optical effect, sufficient mechanical strength, high flexibility, and good workability is desired.

(Means for Solving the Problems) As a result of various studies on solutions to satisfy such demands, the present inventors have found that when a silicon oxide is hydrolyzed to produce an amorphous material, a nonlinear optical material is added to the starting solution. It has been found that an amorphous material having a non-linear optical effect can be easily produced by applying a DC electric field when solidifying an organic molecule after the hydrolysis of silicon oxide is completed after the hydrolysis of the silicon oxide.

That is, the present invention provides a compound represented by the following general formula: Si (OR) ₄ ... (I) (where R is an alkyl group). A method for producing a nonlinear optical amorphous material, wherein during the hydrolysis, an organic compound having a secondary nonlinear optical effect is added and solidified while applying a DC electric field, producing a nonlinear optical amorphous material. The application of the DC electric field, the amorphous body after hydrolysis is placed between the plate-like electrode and the needle-like electrode, a high DC voltage is applied between the two electrodes, and between the two electrodes. There is also a feature in a method for producing a non-linear optical amorphous material which causes corona discharge to charge an amorphous body surface facing a needle electrode.

 Hereinafter, the present invention will be described specifically.

The method for applying a DC electric field to the amorphous material is not particularly limited as long as the amorphous material can be effectively charged. For example, using a corona discharge device shown in the schematic diagram of FIG. A high voltage, for example, a voltage of 5 KV or more, preferably 7 to 12 KV, was applied between the flat electrode 1 and the needle electrode 3 by the DC power supply 4 to generate a corona discharge, and was placed on the flat electrode 1. This is for charging the amorphous sample 2.

According to this method, the nonlinear optical organic molecules are held in the amorphous body in parallel with the DC electric field, and the irregular center is easily formed in the amorphous body. A crystalline material can be easily produced.

The method of producing an amorphous body by hydrolyzing silicon alkoxide is characterized in that it can be synthesized at a low temperature by a method itself called a sol-gel method. Generally, silicon alkoxide is mixed in a solvent such as water or alcohol. The solvent is not particularly limited, but it is preferable to select a solvent that dissolves both the silicon alkoxide and an organic compound having a second-order nonlinear optical effect (hereinafter, simply referred to as a nonlinear organic material), such as water, methanol, and ethyl. Alcohols such as alcohols are preferably used.

In general, the hydrolysis is preferably adjusted under mild conditions at room temperature to about 60 ° C. and by adding an acid or the like to pH 6 to 3 in order to stably and rapidly perform hydrolysis and subsequent dehydration condensation.

Further, it is preferable that the secondary non-linear organic material to be added is previously dissolved in a solvent such as alcohol. The mixture of the silicon alkoxide and the nonlinear organic material is stirred at a low temperature of about room temperature (for example, 20 to 30 ° C.) for about 10 to 30 minutes, transferred to an appropriate container, and then heated to a relatively low temperature of 30 to 80 ° C. By holding at a low temperature for about one hour, an amorphous body having good light-transmitting properties can be obtained.

According to such a sol-gel method, since it can be produced from a solution, there is an advantage that an amorphous material of any shape can be obtained.

Next, a specific description will be given of a process of charging the mixed liquid by corona discharge and centering the nonlinear organic material molecules at an irregular center by the ignition of a DC electric field.

That is, in order to impart a second-order nonlinear optical effect to the amorphous material, it is necessary to align the added nonlinear organic material in one direction and form an irregular center in the amorphous body. To this end, a DC electric field is applied before the mixture solidifies. By this processing, the nonlinear organic material molecule having a large electric dipole moment is oriented in the same direction as the electric field, and an irregular center is formed.

In addition, the nonlinear organic material molecules in the amorphous body cannot move after solidification because they are in a network composed of silicon and oxygen. It is necessary to perform an application process.

The application of this DC electric field is not particularly limited as long as an irregular center is formed in the nonlinear organic material molecules in the amorphous body, but charging by corona discharge is generally suitable.

This is because the target sample is a liquid material and the electrodes cannot be formed by vapor deposition, etc., and the sample contracts when the mixture is solidified. However, corona discharge by a combination of a needle electrode and a plate electrode employed in the present invention is a preferable method.

Further, the mechanism of charging the amorphous body by the corona discharge will be described.

As shown in FIG. 1, an amorphous body sample 2 is placed on a flat electrode 1, and between an amorphous body sample 2 and a needle electrode 3 disposed thereon.
When a high voltage is applied from the DC power supply 4, corona discharge occurs.

In this corona discharge, molecules in the air are ionized, and ions fly toward the opposite electrode, that is, the flat electrode 1. Therefore, a large number of ions 7 are accumulated on the surface of the amorphous body sample 2 and the discharge continues until the needle electrode 3 and the surface of the amorphous body sample 2 become equipotential. During this time, a potential difference is generated between the surface of the amorphous sample 2 and the flat electrode 1 by the amount of the ignition, and the nonlinear organic material molecules in the non-biological sample 2 are held parallel to the electric field. You. As described above, the organic material molecules are easily oriented by the electric field to form an asymmetric center, and in this state, the starting mixture is solidified to produce an amorphous body having an excellent nonlinear optical effect. Can be done.

As the silicon alkoxide represented by the general formula used in the present invention: Si (OR) ₄ (I) (where R is an alkyl group), specifically, silicon methoxide, silicon ethoxide and the like Can be mentioned.

The second-order nonlinear organic material used in the present invention includes:
Any known one may be used, for example, 2-methyl-
Examples thereof include 4-nitroaniline, 3-acetamido-4-dimethylaminonitrobenzene, and p-nitroaniline.

(Operation) In the present invention, prior to solidification of the liquid mixture of the secondary nonlinear organic material and the amorphous material, the secondary nonlinear organic material is charged by corona discharge according to the method of the present invention, and the subsequent charging is performed. Since the orientation and asymmetric centering in the amorphous body can be effectively performed, the orientation of the second-order nonlinear organic material can be aligned in one direction in a very orderly manner, and an amorphous body having a high-quality nonlinear effect can be obtained. There is a function to be performed.

The present invention will be specifically described by the following examples (comparative examples), but these do not limit the scope of the present invention.

Example 1 Silicon methoxide 10 ml, methanol 12 ml, water 12 ml,
0.2 ml of nitric acid is placed in a glass beaker, and 0.9 g of 2-methyl-4-nitroaniline is dissolved as a nonlinear organic material. This mixed solution is stirred for about 30 minutes, the solution is taken with a 1 ml dropper, dropped on a glass substrate, and the glass substrate is placed on the flat electrode 1 shown in FIG. The needle electrode 3 is set at a position 1 cm above the glass substrate, and a DC voltage of 10 kv is applied between both electrodes. The needle electrode 3 side was set to a negative voltage. Corona discharge was generated between the two electrodes, and the state where a voltage was applied was maintained for about one hour. During that time, the solution was brought to about 40 ° C., and after confirming that it had solidified, a sample was taken out. The sample was a yellow translucent amorphous body.

In order to confirm non-linear effects, when the YAG laser having a wavelength of 1.06 f m was applied to the sample, and emitted green light. Since this is the second harmonic generation phenomenon which is a typical example of the second-order nonlinear effect, it is understood that the sample has the second-order nonlinear effect.

Example 2 10 ml of silicon ethoxide, 10 ml of ethanol, 10 ml of water,
3-acetamide-4 as a non-linear organic material in 0.2 ml of hydrochloric acid
0.5 g of dimethylaminonitrobenzene was dissolved, and an amorphous product was obtained in the same manner as in Example 1.

Since this sample also generates the second harmonic, it can be seen that the sample has a second-order nonlinear effect.

(Effect of the Invention) As described above, in the present invention, the nonlinear optical material can be easily oriented and irregularized in the amorphous body by utilizing the corona discharge phenomenon caused by the application of the DC electric field. It is effective when used in the field of optoelectronics.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a DC corona discharge generator used to carry out the method of the present invention. 1: Flat electrode 2: Sample 3: Needle electrode 4: DC power supply 5: Ground 6: Corona discharge 7: Charge charged on the sample surface

Claims (2)

(57) [Claims] (1) A silicon alkoxide represented by the general formula: Si (OR) ₄ ... (I) (where R is an alkyl group) is hydrolyzed by adding water and alcohol, and solidified. A method for producing a nonlinear optical amorphous material, characterized in that an organic compound having a secondary nonlinear optical effect is added during the hydrolysis and solidified while applying a DC electric field. Method of manufacturing quality materials. 2. The method according to claim 1, wherein the application of the DC electric field comprises placing an amorphous body after hydrolysis between the plate-like electrode and the needle-like electrode, applying a high DC voltage between the two electrodes, The method for producing a nonlinear optical amorphous material according to claim 1, wherein a corona discharge is caused to charge the surface of the amorphous body facing the needle electrode.