JPH02188727A - Nonlinear optical material - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an electro-optical device, a second harmonic generation device,
The present invention relates to novel nonlinear optical materials useful for wavelength conversion devices, piezoelectric devices, optical waveguides, etc., optical memory light sources, laser printer light sources, optical switches, etc.

[Prior art]

In recent years, materials with nonlinear optical effects (a phenomenon in which when a strong laser beam is incident on a material, an emitted light with a different component from the incident light is obtained due to the interaction) are being used as electro-optic devices and second harmonic generation. device, wavelength conversion device,
It is attracting attention as a material useful for optical memory light sources, etc. Such nonlinear optical materials are introduced in detail in the following literature.

”Non1inear 0ptical Proper
Ties of Organic and Polyme
ric Materials"AC8SYMPO5IU
M 5ERIES 233. David J,%1i
11iams edition (Ameriacn Che-mica
``Organic Nonlinear Optical Materials'' edited by Masao Kato and He Nakanishi (CMC Publishing Co., Ltd., published in 1983); "Organic Electronic Materials" edited by Akio Taniguchi (Science Forum Publishing Co., Ltd., published in 1986)
.

Potassium dihydrogen phosphate has traditionally been used as a nonlinear optical material mainly for second harmonic generation devices (based on second-order nonlinear optical effects) and wavelength conversion devices (those using sum and difference frequencies). (KDP), ammonium dihydrogen phosphate (ADP), lithium niobate, and other inorganic materials. On the other hand, in recent years, it has been discovered that π-electron conjugated organic compounds such as p-nitroaniline, which have an electron-donating group and an electron-withdrawing group, exhibit various properties that far exceed those of the above-mentioned inorganic compounds as nonlinear optical materials. , research on this type of organic compound is being actively conducted.

In general, in the case of organic nonlinear optical materials, each molecule exhibits a nonlinear optical response, and the nonlinear optical performance of each molecule is determined by its molecular hyperpolarizability (molecular hyperpolarizability).
arizability).

For example, even if p-nitroaniline exhibits high second-order nonlinear performance in its molecular state (that is, even if it has a large β), when it becomes a crystal, the molecular arrangement has central symmetry. There are many cases in which no second-order nonlinear optical effect is exhibited. In addition, by introducing a methyl group into the ○-position of this p-nitroaniline, we succeeded in breaking the symmetry of the crystal without reducing the performance of the molecule (i.e., the size of β).
Methyl-4-nitroaniline (MNA) has a large SHG tensor (B, F, Levine
, et al., J. Appl, Phys., 5
0.2523 (1970)], which does not satisfy the phase matching conditions for efficiently extracting SHG, and therefore it is difficult to effectively utilize its large nonlinear optical performance.

Furthermore, it is difficult to obtain a single crystal of MNA, and there are many problems in applying it as a device.

The same is true for, for example, dimethylaminonitrostilbene, which has an electron-donating group and an electron-accepting group introduced into the stilbene skeleton, and has been found to have a large β, but because it has central symmetry in the crystalline state, , does not exhibit second-order nonlinear performance, and absorption is on the long wavelength side (λmax = 58
0 nm), so even if it were possible to break the central symmetry, it would be disadvantageous to use it as a device such as SHG.

Also, for example, 4-chloro-4' with other stilbene skeletons
- Diethylaminostilbene has a relatively large β;
It is known that the absorption wavelength is shorter than that of dimethylaminonitrostilbene (J, L, Oudar
, J. Chew, Phys., 67, No. 2,
446 (1977)), it was unclear whether the crystalline state would necessarily show good performance.

In addition, asymmetric carbon atoms are introduced into known SHG active skeletons (
J.L., Oudar, et al., J.A.
ppl, Phys.

48, 2699 (1977)), dispersing high-performance molecules in polymers and poling them with an electric field (Japanese Patent Application Laid-open No. 61-1921-1)
Although methods such as 186942) have been considered, good results have not always been obtained.

[Problem to be solved by the invention]

In view of the above circumstances, an object of the present invention is to provide a novel organic nonlinear optical material that exhibits a large nonlinear optical effect.

[Structure and operation of the invention]

The nonlinear optical material of the present invention is represented by the general formula (where R1 and R may be the same or different and represent a hydrogen atom, a substituted or unsubstituted alkyl group, or a substituted or unsubstituted aryl group) It consists of compounds.

The present inventors have repeatedly conducted various studies to solve the above-mentioned problems in the prior art, and found that among various stilbene derivatives, a specific stilbene derivative represented by the above general formula has a large nonlinear optical effect. This discovery led to the present invention.

Examples of the alkyl group in the above general formula include methyl group, ethyl group, propyl group, L-propyl group, butyl group,
Examples include t-butyl group, octyl group, t-octyl group, decyl group, etc., but those with a low carbon number are preferred.

In addition, these alkyl groups can be converted into phenyl groups, hydroxy groups,
Examples include those substituted with a carboxyl group, an alkoxycarbonyl group, a nitrile group, a halogen atom, etc. (eg, benzyl group, hydroxymethyl group, 4-methylbenzyl group, 2-carboxyethyl group, ethoxycarbonylmethyl group, etc.). Examples of the aryl group include phenyl, naphthyl, anthryl, etc., with phenyl being particularly preferred, and examples including phenyl groups substituted with lower alkyl, lower alkoxy, halogen, nitrile, etc. (For example, 4-chlorophenyl group, 4-methoxyphenyl group, 4-methylphenyl group, 2,4-dimethylphenyl group, 4-cyanophenyl group, etc.).

All of the stilbene derivatives of the above general formula of the present invention are nonlinear optical materials that exhibit large nonlinear optical effects, and specific examples thereof are as follows.

α1° These compounds can be synthesized, for example, by a modified Wittig reaction. That is, as shown in the reaction formula below, the desired stilbene derivative is obtained by reacting the phosphonic acid ester derivative (A) obtained by the M1chalis-A rvuzov reaction with the aldehyde compound (B) in the presence of a basic catalyst. Can be done.

The present invention will be explained below by way of examples.

EXAMPLE The nonlinear optical performance of the compounds (1), (4), (5), and (6) was measured.

Second harmonic generation (
SHG) measurements to S, Kurtz and T, T, Per.
ry J, Appl, Phys, 39,3798 (19
This was carried out by the method published in 68). This method is a method in which a sample powder is irradiated with a strong laser beam and the intensity of the generated SHG is measured with respect to a reference material, and the approximate second-order nonlinear performance can be estimated.

The light source laser is a high-power Nd”:YAG laser.
The oscillation wavelength of the (Nd”:YAG laser using (250+aJ/pulse, pulse width ~20ns) is 1.064
μmaro, and when this light is irradiated on SHG active material, 5
32 rus of green SHG is obtained).

When a sample is filled in a quartz glass cell and irradiated with a laser beam, the SHG from the sample is observed to be scattered both forward and backward with respect to the direction in which the laser beam travels. The strength was measured. The detector at this time is a photomultiplier tube, which cuts the laser light with an infrared absorption filter, and uses an interference filter to
Only nm SHG was taken out.

At this time, the particle size of the sample was not screened, and the reference material was urea with an average particle size of 100 μm.

-(NH,)I2PO4: ammonium dihydrogen phosphate) [
Effects of the Invention] As is clear from the Examples, the compounds of the present invention are effective as nonlinear optical materials. That is, the compound of the present invention is effective as a nonlinear optical material that can be used even in a crystalline state. In addition, since all the compounds of the present invention exhibit large nonlinear optical performance,1 for example, the above compounds also have a large β
It is expected that the Therefore, the compound of the present invention can provide great nonlinear optical performance not only in a crystalline state but also when dispersed or poled in a polymer as in the prior art. Furthermore, by making the compound of the present invention into a single crystal, it can be applied to an SHG device as shown in FIG. 1 (in the figure, 1 is a semiconductor laser and 2 is a single crystal of the material of the present invention).

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of an example of an SHG device using the nonlinear optical material of the present invention.

Claims (1)

[Claims] 1. General formula ▲ Numerical formula, chemical formula, table, etc. ▼ (However, R_1 and R_2 may be the same or different,
Represents a hydrogen atom, a substituted or unsubstituted alkyl group, or a substituted or unsubstituted aryl group. ) A nonlinear optical material consisting of a compound represented by