JPH02171730A - Nonlinear optical material and nonlinear optical element - Google Patents

Abstract

PURPOSE:To obtain a high nonlinear optical effect without having absorption of visible light by constituting the nonlinear optical material of the compds. selected from 3-hydroxy-4-methoxynitrobenzene, p-nitrobenzonitrile, p- nitrobenzaldehyde, etc. CONSTITUTION:The nonlinear optical element is formed by using the nonlinear optical material consisting of the compds. selected from the 3-hydroxy-4- methoxynitrobenzene, p-nitrobenzonitrile, p-nitrobenzaldehyde, etc. These compds. can have substituents within the range where the high nonlinear optical effect, the absorptivity of visible light and crystallinity are not largely impaired. The formation of the nonlinear optical element in various forms such as blending of the compds. in polymers and liquid crystal molecules, etc. The intensity of second harmonic waves can be measured by using an Nd:YAG laser 1 and integrating the output voltage of a photomultiplier 6 by a boxcar integrator 7. The nonlinear optical material and nonlinear optical element which have no absorption of visible light and exhibit the high nonlinear optical effect are obtd. in this way.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to organic nonlinear optical materials and organic nonlinear optical elements used for generation of harmonics of laser light, parametric amplification, and the like.

[Background of the Invention] Nonlinear optical effects that appear prominently when materials are irradiated with intense light such as laser light are second harmonic generation (SHG),
It can be applied to third harmonic generation (THG), intensity modulation, switching, optical memory, etc., and the application of nonlinear optical materials having nonlinear optical effects to next-generation optical devices is attracting attention.

In recent years, exploration research into nonlinear optical materials has been actively progressing, and in particular, regarding the SHG effect, organic materials such as previously known lithium niobate (LiNb03) and potassium dihydrogen phosphate (KDP) have been developed. It has been pointed out that they may have orders of magnitude higher performance than inorganic materials in terms of nonlinear optical constants, response speed, durability, etc. (For example, [Organic Nonlinear Optical Materials] Masao Kato, Supervised by Nakanishihe Department,
(CMC Publishing, 1985) In addition, there is active research into crystal growth of nonlinear optical materials, devices using nonlinear optical materials, etc., and in particular 5) (wavelength conversion elements using G and THG) It is strongly desired to obtain an optical waveguide device which has high conversion efficiency and can emit light with uniform phase.

Examples of compounds with SHG effect include 2-methyl-4
-nitroaniline (MNA), 2-acetamide-4
-Nitro-N,N-dimethylaniline (DAN), 2-
Acetamido-4-nitro-1-pyrrolidinobenzene (
PAN), 2-(α-methylbenzyl)amino-5-nitropyridine (MBA-NP>, etc.) are known.

These are materials with a large and excellent nonlinear optical effect among the conventionally known compounds with the SHG effect, but the organic nonlinear optical materials represented by these materials are large enough to be used as the core of an optical waveguide. In particular, it was extremely difficult to use a single crystal as an optical waveguide for use as a wavelength conversion element.

For example, conventionally, in order to create a fiber-type optical waveguide device, a nonlinear optical material with a high refractive index is melted and injected into a hollow fiber made of a material with a low refractive index, and then a simple method such as the Bridgman-Stockberger method is used. A method of crystallization is used. (Reference Library, S., Chela, J.
, 2yss: Non1inear Optical
Properties or OrganicMo
1eculesand Crystals Vol, 1
ACADE Formerly CPRESS INC However, conventionally known organic nonlinear optical materials that exhibit excellent nonlinear optical effects generally cannot be made into single crystals by this method.
It is difficult to form the core of an excellent optical waveguide. For example, PAN and MBA-NP decompose when melted, making it impossible to obtain a single crystal.

In addition, research into optical recording media is being actively conducted in response to demands for larger capacity and higher density information recording media, but since the recording density of these optical recording media depends on the wavelength of the light source (
As the light source wavelength becomes shorter, the recording density limit increases in inverse proportion to the square of the wavelength. ), there are great expectations for wavelength conversion elements to obtain shorter wavelength light sources (for example, to obtain blue light from near-infrared light, which is the oscillation range of semiconductor lasers), but conventional excellent organic nonlinear optics Many of the materials (e.g. MN
A, DAN) was colored yellow and had low transmittance for blue light, so it was disadvantageous to use as a wavelength conversion element that generates blue light.

Therefore, it has been strongly desired to develop an organic nonlinear optical material that is easily formed into a single crystal and has high light transmittance in the visible region, particularly blue light.

The origin of nonlinearity in organic compounds is the intramolecular π electrons, and 2
The following nonlinear molecular polarizability β becomes particularly large when the compound has both an electron-donating group and an electron-withdrawing group.

However, even if the nonlinear polarization at the molecular level is large, as typified by p-nitroaniline, there are many compounds that do not exhibit total <SHG in the crystalline state, or even if they do, the SHG is small, making the compound superior. Whether or not a compound exhibits a nonlinear optical effect cannot be determined from the second-order nonlinear molecular polarizability β of the compound.

The present inventors conducted research on the nonlinear optical effect, crystallization, and visible light transmittance of the compound, and found that it has a high nonlinear optical effect, no absorption of visible light, and is sufficient to be easily used as an optical waveguide. We have discovered a compound that forms crystals of a large size.

[Objective of the Invention] The object of the present invention is to provide a nonlinear optical material that can easily form a single crystal large enough to be used as an optical waveguide, does not absorb visible light, and exhibits a high nonlinear optical effect; An object of the present invention is to provide an optical element.

[Structure of the Invention] The above objects of the present invention are: (1) 3-hydroxy-4-methoxynitrobenzene, P-nitrobenzonitrile, p-nitrobenzaldehyde, m-nitrophenol, ρ-nitrobenzyl bromide, 3-bromo- 4'-chloro-4-nitrobenzophenone, 4-nitrophthalimide, 4-hydroxy-
A special linear optical material comprising a compound selected from 3-methoxybenzonitrile, 4-amino-1-naphthalenecarbonitrile, and phenylrohydroxybenzoate.

(2) A nonlinear optical material element made of the nonlinear optical material described in item (1) above.

achieved by.

The present invention will be explained below.

The compounds used in the present invention are (1) 3-hydroxy-4-methoxynitrobenzene (2) p-nitrobenzonitrile (3) p-nitrobenzaldehyde (4) m-ditrophenol (5) P-nitrobenzyl bromide (6) 3-bromo-4'-chloro-4-nitrobenzophenone (7) 4-nitrophthalimide (8) 4-hydroxy-3-methoxybenzonitrile (9) 4-amino-1-naphthalenecarbonitrile (10) ) Phenyl p-hydroxybenzoate.

The above compound can have a substituent within a range that does not significantly impair the high nonlinear optical effect, visible light absorption, and crystallinity of the above compound.

The compounds described in the claims also refer to compounds having the above substituents.

The compounds of the present invention can be used in nonlinear optical elements in various forms such as single crystals, powders, solutions, thin films deposited on supports (Langmuir-Prodgett films, vapor-deposited films, etc.), or blended into polymers or liquid crystal molecules. can do. It is also possible to pendant the compound of the present invention to a polymer, or use it as an inclusion compound or adduct.

The shape of the element can be a known waveguide shape.9 For example, as shown in Japanese Patent Application Laid-Open No. 63-77035, a fiber shape, a groove shape, or a shape in which a single crystal is surrounded by a cladding material are used. be.

The nonlinear optical element of the present invention can be used for wavelength conversion of laser light (generation of harmonics, etc.), intensity modulation, switching, and the like.

[Example] Examples will be shown below, but the embodiments of the present invention are not limited thereto.

Example 1 A commonly used powder method for determining 5HG effects [S, Kurtz, T, T, Perry;
J. AppPhys., 39.3798 (1968
) ) was used to evaluate the compounds of the present invention.

FIG. 1 is an explanatory diagram showing this measurement system.

In Fig. 1, 1 is a Nd: YAG laser, 2 is a sample, 3 is a condenser lens, 4 is an infrared cut filter,
5 is a monochromator, 16 is a photomultiplier, and 7 is a boxcar integrator.

Beam diameter 2 aat+ as incident fundamental wave, repetition 1
0pps, pulse @10ns, pulse energy 2
Q switch Nd of 01J: YAG laser light (wavelength 1064 nn).

US Quantel International 1 Company Y
G660A) was used.

The second harmonic (532nl green light) generated by vertically irradiating the incident fundamental wave onto a powder sample filled in a glass cell
The fundamental wave was separated using an infrared cut filter and a monochromator, and detected using a photomultiplier tube. Second
The intensity of the harmonics was measured by integrating the output voltage of the photomultiplier tube with a boxcar integrator.

When the sample was irradiated with the incident fundamental wave, circularly polarized light was used to eliminate the dependence on the light intensity.

Using urea as a standard sample, the relative intensity was determined when the second harmonic of urea was set to 1, and the sample was evaluated.

These results are shown in Table-1.

Margin Table-1 Below: In order to examine the transmittance of blue light (wavelength around 430nl), a methanol solution of the compound of the present invention (concentration 0.0nl) was prepared.
The transmission spectrum of 2ffilr/a+I) was measured using a spectrophotometer (U-3410' manufactured by Hitachi, Ltd.), and the value corresponding to 1% of the peak on the longest wavelength side was read from the absorption curve and taken as the absorption edge.

These results are shown in Table-2.

Table 2 ”; (1): 3-Hydroxy-4-methoxynitrobenzene (2): p-nitropenzonitrile (3): p-nitrobenzaldehyde (4): m-nitrophenol (5): ρ-Nitrobenzyl bromide (6): 3-
Bromo-4'-chloro-4-nitrobenzophenone (7
): 4-nitrophthalimide <8): 4-hydroxy-3-methoxybenzonitrile <9): 4-amino-1-naphthalenecarbonitrile (
10): Phenyl p-droxybenzoate"; 3
80 Intensity is expressed as a relative value when urea is set to 1°1;
Example 2 Same as Table 1 The compound of the present invention is heated to a temperature 10°C higher than the melting point,
The melt was injected into a hollow glass fiber made of borosilicate glass with an outer diameter of 1.0 mm, an inner diameter of 7 μm, and a length of 50 IuI using capillary action.

Thereafter, using the Bridgman-Stockberger method, the hollow glass fiber injected with the compound was pulled from a heating furnace maintained at a temperature 5°C higher than the melting point of the compound at a pulling rate of 1 sushi per hour. It was cooled and crystallized.

The length of the single crystal portion was measured using a polarizing microscope.

These results are shown in Table 3.

Margin table-3 below Same as Table-1 A: Length of the obtained single crystal 10 or more B: Length of the obtained single crystal 1 or more but less than 10 C: Length of the obtained single crystal 0 .2- or more and less than 111 wI D: The material decomposes during melting and a single crystal cannot be obtained. Example 3 The single crystal fiber of compound (1) (8) obtained in Example 2 was made into a length of about 3 ll+u. Cut out, repeat as incident fundamental wave 10pps, pulse Q 10ns
, Q-switch Nd with pulse energy 320 IIJ
: YAG laser (USA [11Quantel In
ternationa1 YG660A.

When this was attenuated and focused and guided from the end face of a single crystal fiber, a ring-shaped second harmonic (green light) was observed on the screen.

[Effects of the Invention] According to the present invention, a nonlinear optical material and a nonlinear optical element that can easily obtain a single crystal large enough to be used as an optical waveguide, do not absorb visible light, and exhibit high nonlinear optical effects. can be provided.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing a second harmonic measurement system using the powder method. Diagram

Claims (2)

[Claims] (1) 3-hydroxy-4-methoxynitrobenzene,
p-Nitrobenzonitrile, p-nitrobenzaldehyde, m-nitrophenol, p-nitrobenzyl bromide, 3-bromo-4'-chloro-4-nitrobenzophenone, 4-nitrophthalimide, 4-hydroxy-3
- A nonlinear optical material comprising a compound selected from methoxybenzonitrile, 4-amino-1-naphthalenecarbonitrile, and phenyl p-hydroxybenzoate. (2) A nonlinear optical element made of the nonlinear optical material according to claim (1).