JPH03196027A - Nonlinear optical material and nonlinear optical element - Google Patents

Abstract

PURPOSE:To obtain the material and element hardly forming symmetry by inversion in the bulk state of a crystal, a thin film, etc., and producing a significant nonlinear optical effect by using a specified compd. CONSTITUTION:A compd. represented by formula I is used. In the formula I, each of R1 and R2 is H or optionally substd. alkyl, R1 and R2 may bond to each other to form a hetero ring together with N and A is an electron attractive group having >=0 sigmap defined by the Hammett's rule, e.g., nitro, cyano, formyl, alkylsulfonyl, sulfamoyl or carboxy. The material and element hardly forming symmetry by inversion in a service form and highly generating second harmonics is obtd.

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] The nonlinear optical effect that appears when a material is irradiated with intense light such as a laser beam can be applied to wavelength conversion, intensity modulation, switching, etc., and in recent years, materials that have this nonlinear optical effect have been developed. Many exploratory studies have been conducted.

Wavelength conversion, especially second harmonic generation based on second-order nonlinear optical effects.
eratIon.

Hereinafter abbreviated as SHG. ), it has been pointed out that organic compounds may have an order of magnitude higher performance than conventionally known inorganic materials such as lithium niobate (L i Nb01) and potassium dihydrogen phosphate (KDP). (for example,
"Organic Nonlinear Optical Materials", supervised by Masao Kato and Hebe Nakanishi, CMC Co., Ltd.

(published in 1985) 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, as typified by p-nitroaniline, even if the nonlinear polarization at the molecular level is large, there are many that do not exhibit total<SHG in the crystalline state, or even if they do, the SHG is small. This is due to the fact that the molecular arrangement of highly polar organic crystals tends to have inversion symmetry.

[Objective of the Invention] Therefore, an object of the present invention is to provide a novel organic nonlinear optical material and an organic nonlinear optical element that are unlikely to exhibit inversion symmetry in a bulk state such as a crystal or thin film and exhibit high nonlinear optical effects. .

[Structure of the Invention] The above objects of the present invention are as follows: (1) A nonlinear optical material characterized by comprising a compound represented by the following general formula [I1].

General formula [N [In the formula, R1 and R2 each represent a hydrogen atom or a substituted or unsubstituted alkyl group. Further, R and R1 may jointly form a heterocycle with a nitrogen atom.

A represents an electron-withdrawing group. ] (2) A nonlinear optical element made of the nonlinear optical material described in (1) above.

achieved by.

The present invention will be explained in more detail below.

In the above general formula [I], the alkyl group represented by R1 and R2 may be linear, branched or cyclic, and specifically, for example, methyl group, ethyl group, propyl group, i- Examples include propyl group and cyclohexyl group. Further, the substituent that the alkyl group may have is not particularly limited as long as it does not inhibit crystal orientation, and examples thereof include a halogen atom and a cyano group.

R8 and R2 may jointly form a heterocycle with the nitrogen atom, such as a pyrrolidine ring or a pyrazole ring. These heterocycles may have a substituent.

Preferred examples of R3 and R1 include those in which either R1 or R2 is a substituted or unsubstituted alkyl group;
1 and R2 together form a heterocycle with a nitrogen atom, more preferably R4 and R2 both represent a substituted or unsubstituted alkyl group, and R1 and R2 together form a heterocycle with a nitrogen atom. It forms a heterocycle.

The electron-withdrawing group represented by A is a group whose σp defined by Hammett is 0 or more, such as a nitro group, a cyano group, a formyl group, an alkylsulfonyl group (e.g., a methylsulfonyl group, an ethylsulfonyl group), a dicyano group, etc. Vinyl group, alkoxycarbonyl group (e.g. methoxycarbonyl group, ethoxycarbonyl group), trifluoromethyl group, carbamoyl group (e.g. methylcarbamoyl group, phenylcarbamoyl group), sulfamoyl group (e.g. methylsulfamoyl group), carboxy group. It will be done. Among these, preferred are a nitro group, a formyl group, and an alkoxycarbonyl group, with a nitro group being more preferred.

Specific examples of compounds preferably used in the present invention are shown below, but the present invention is not limited thereto.

The following margins (1) (2) These compounds can be easily synthesized by the boat fishing synthesis method.

Synthesis Example [Synthesis of Exemplified Compound (2)] (3) (4) (5) Dissolve 10 g of 1 in 200 ml of N,N-dimethylformamide, and further add methyl iodide tog and 5 g of potassium t-butoxy. The container was sealed and reacted at 60°C for 3 hours. The reaction solution was poured into ice water, extracted with ethyl acetate, purified by column chromatography, and then recrystallized from methanol to obtain 2 g of crystals of Exemplary Compound (2).The structure was confirmed by mass spectrometry and NMH.

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-Blodgett 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. For example, as shown in Japanese Unexamined Patent Publication No. 63-77035, there are fiber shapes, flat plate shapes, and shapes in which a single crystal is surrounded by a cladding material.

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, Appl.

The compounds of the present invention were evaluated using Phys., 39.3798 (198 g).

The light source was a Q-switched Ndr YAG laser (Quantel, USA) with a beam diameter of 2 mm, repetition rate of 10 pps, pulse width of 10 ns, and pulse energy of 20 mJ.
Inter-flat10na1 YGli60A
, wavelength IQB 4 nm) was used to irradiate a powder sample filled in a glass cell, and the generated SMC light (53
2 nm green light) was spectrally analyzed using a filter and a monochromator, detected using a photomultiplier tube, and the relative value when urea was taken as 1 was determined.

Table 1 As is clear from Table 1, the compound of the present invention has a strong SHG strength and is an excellent nonlinear optical material.

Example 2 A single crystal of the compound of the present invention used in Example 1 was formed in a hollow fiber using the Bridgman-Stockberger method [formation conditions: temperature of high temperature furnace; (melting point of compound) + (5 °C), the temperature of the low temperature furnace; (melting point of the compound)
- (20°C), pulling rate: 1/hour], a nonlinear optical element was produced.

When YAG laser light with a wavelength LO of 64 nm was input from the end face of the fiber, a second harmonic of 582 rv was observed.

[Effects of the Invention] According to the present invention, it is possible to provide an organic nonlinear optical material and an organic nonlinear optical element that are unlikely to have inversion symmetry when used and can provide high SHG.

Claims (2)

[Claims] (1) A nonlinear optical material comprising a compound represented by the following general formula [I]. General formula [I] ▲ Numerical formulas, chemical formulas, tables, etc. are available▼ [In the formula, R_1 and R_2 each represent a hydrogen atom or a substituted or unsubstituted alkyl group. Also, R_1 and R_2
may form a heterocycle together with a nitrogen atom. A represents an electron-withdrawing group. ] (2) A nonlinear optical element made of the nonlinear optical material according to claim (1).