JPH0240633A - Nonlinear optical material and nonlinear optical element - Google Patents

Abstract

PURPOSE:To obtain the org. nonlinear optical material and org. nonlinear optical element which hardly attain inverse symmetry in a bulk state such as crystal or thin film and have substantially no absorption in a visible region by using the compd. expressed by the special formula. CONSTITUTION:The nonlinear optical material and nonlinear optical element are formed by using the compd. expressed by the formula (I). In the formula, A denotes an electron-withdrawing group; R1 denotes a substd. alkyl group; R2 denotes a univalent substituent. n denotes 0-3 integer. Plural R2 may be the same or different and the adjacent R2 may combine each other to form a ring when n is >=2. The electron-withdrawing group expressed by A is, for example, a nitro group, formyl group, etc.

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
ratlOn (hereinafter abbreviated as SHG), organic compounds may have an order of magnitude higher performance than conventionally known inorganic materials such as lithium niobate (LiNbO) and potassium dihydrogen phosphate (KDP). has been pointed out. (
For example, "Organic Nonlinear Optical Materials", supervised by Masao Kato and Hehe 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 represented by ρ-nitroaniline, nonlinear polarization at the molecular level Even if they are large, there are many cases where they do not show total<SHG in the crystalline state, or even if they do show, the SHG is small. This is due to the fact that the molecular arrangement of highly polar organic crystals tends to have inversion symmetry.

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 in order to obtain shorter wavelength light sources.

However, known compounds with high SHG activity, such as 2-methyl-4-nitroaniline, m-nitroaniline, etc., are yellow-colored, so they have low transmittance to short-wave light, and they cannot be used for short-wave light by wavelength conversion. It is disadvantageous for this to occur. Therefore, a nonlinear optical material is desired that has high transmittance in the visible region, particularly in short-wavelength light.

[Objective of the Invention] Therefore, the object of the present invention is to provide a novel organic nonlinear optical material that is difficult to exhibit inversion symmetry in a bulk state such as a crystal or a thin film, has substantially no absorption in the visible region, and exhibits a high nonlinear optical effect. An object of the present invention is to provide an organic nonlinear optical element.

[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 [11].

General formula [11 (wherein, A is an electron-withdrawing group, R1 is a substituted alkyl group, R
2 represents a monovalent substituent, nl represents an integer from O to 3,
When n is 2 or more, a plurality of R2s may be the same or different, or adjacent R2s may be linked to each other to form a ring. )<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 electron-withdrawing group represented by A is a group with σp>0 defined by Hammett,
For example, nitro group, formyl group, carbamoyl group (e.g. methylcarbamoyl group, phenylcarbamoyl group, etc.),
Carboxy group, sulfamoyl group (e.g. methylsulfamoyl group, etc.), oxycarbonyl group (e.g. methoxycarbonyl group, ethoxycarbonyl group, etc.), cyano group,
Examples include dicyanovinyl group.

Among these, preferred are a nitro group, a formyl group, a cyano group, and an alkoxycarbonyl group.

The electron-withdrawing group represented by A is preferably in the para position with respect to -OR.

Examples of the substituent of the substituted alkyl group represented by R2 include a halogen atom, an alkoxy group, a cyan group, and a nitro group.

Among these, preferred is a halogen atom, and even more preferred is a bromine atom.

The monovalent substituent represented by R2 is not particularly limited and may be either an electron-donating group or an electron-withdrawing group, but π
A group that does not significantly affect the electronic conjugation system is preferable.

The electron-withdrawing group is σp defined by Hammett.
>O, such as nitro group, cyano group, alkylsulfonyl group (e.g. methylsulfonyl group, ethylsulfonyl group, etc.), formyl group, carbamoyl group (e.g. methylcarbamoyl group, phenylcarbamoyl group, etc.), sulfamoyl group (e.g. methylsulfamoyl group, etc.),
Examples thereof include oxycarbonyl group (eg, methoxycarbonyl group, ethoxycarbonyl group, etc.), dicyanovinyl group, and carboxy group.

The electron donating group is a halogen atom or a group with σp<O defined by Hammett, for example, an amino group (
(groups such as amino, methylamino, dimethylamino, L-2-hydroxymethyl-1-pyrrolidinyl), hydroxyl groups, alkoxy groups (groups such as methoxy, ethoxy, butoxy), alkyl groups (groups such as methyl, ethyl, propyl, etc.) ) etc.

When n is 2 or more, examples of the condensed ring formed by connecting adjacent R2s include naphthalene, anthracene, indole, quinoline, benzimidazole, and the like.

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

These compounds can be easily synthesized by introducing an electron-withdrawing group represented by A into a substituted alkoxybenzene derivative or by reacting a phenol derivative with a substituted alkyl halide using numerical synthesis methods. Can be done.

In addition, some of these compounds are generally available as commercially available reagents (e.g., Kanto Kagaku, Tokyo Kasei, Wako Pure Chemical, AIdr
It is easily available as a product of ich company).

Synthesis Example (Synthesis of Exemplified Compound 1) 100 m of p-nitrophenol sodium of 20.
1 was dissolved in dimethylformamide, 26° dibromoethane was added dropwise thereto, and the mixture was reacted at room temperature for 10 hours.
The reaction solution was poured into dilute hydrochloric acid, and the precipitated crystals were recrystallized from acetonitrile to obtain 18 g of crystals of the desired product.

The structure was confirmed by NMR and FD-mass spectra.

Melting point: 66-67°C The compound of the present invention can be in various forms such as single crystal, powder, solution, thin film deposited on a support (Langmuir-Prodgett film, vapor deposited film, etc.), or blended into polymer or liquid crystal molecules. It can be made into a nonlinear optical element in the form of a nonlinear optical element. 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 Patent Application Laid-Open No. 63-77035, a fiber shape, a flat plate shape, or a shape in which a single crystal is surrounded by a cladding material are available. be.

The nonlinear optical element of the present invention has a wavelength change jA(
It can be used for harmonic generation, etc.), intensity modulation, switching, etc.

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

Example 1 Powder method that has been unsuccessfully used to determine the effect of 5HG (S., Kurtz, T., T. Perry;
J.AOOI.

Phys., 39.3798 (1968)) was used to evaluate the compounds of the present invention.

As a light source, a Q-switched Nd:YAG laser (manufactured by Quantel, USA) with a beam diameter of 2 cm, repetition rate of 10 pps, pulse width of 1 Qns, and pulse energy of 201 J was used.
Inter-rlatiOna1 YG 660
The generated SHG light (
532ni green light) was separated using a filter and a monochromator, detected using a photomultiplier tube, and the relative value when urea was taken as 1 was determined.

Furthermore, absorption in the visible region in methanol was also measured, and the results are also shown in Table 1.

Table 1 As is clear from Table 1, the compound of the present invention has a strong SHG intensity and substantially no visible absorption, which indicates that it is an excellent nonlinear optical material that can be used even with shorter wavelength light.

Example 2 As a light source, a dye laser (USA 1 Spectra Physics PDL-
2.

Example 1
Measure the blue light intensity of 431n11 in the same way as 2.
The relative value when -methyl-4-nitroaniline (MNA) is set to 1 was determined. The results are shown in Table 2.

It can be seen that this is a nonlinear optical material that is particularly excellent in generating colored light.

Example 3 The compound of the present invention used in Example 1 was formed in a hollow fiber to create a nonlinear optical element. When a YAG laser beam with a wavelength of 11064n was input from the end face of the fiber, a second harmonic of 532nn+ 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 have substantially no absorption in the visible region, are unlikely to exhibit inversion symmetry in the form of use, 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] ▲There are mathematical formulas, chemical formulas, tables, etc.▼ (In the formula, A is an electron-withdrawing group, R_1 is a substituted alkyl group,
R_2 represents a monovalent substituent. n represents an integer of 0 to 3. When n is 2 or more, a plurality of R_2 may be the same or different, or adjacent R_2 may be connected to each other to form a ring. ) (2) A nonlinear optical element made of the nonlinear optical material according to claim (1).