JPH05341337A - Nonlinear optical material - Google Patents

Abstract

PURPOSE:To obtain the nonlinear optical material which exhibits a high nonlinear optical effect by constituting the material of the benzoxazole compd. expressed by a specific formula. CONSTITUTION:This nonlinear optical material consists of the benzoxazole compd. expressed by the formula. In the formula, R denotes a hydrogen atom, alkyl group, halogen atom, substd. or unsubstd. phenyl group or nitro group; Ar denotes a substd. or unsubstd. arom. group; n denotes 0, 1 or 2. In the formula, the arom. group includes polycyclic arom. groups, such as phenyl group, naphthalene, anthracene and pyrene; the substituents of the arom. groups include a substd. amino group, hydroxy group, substd. or unsubstd. alkoxy group, substd. or unsubstd. alkyl group, substd. or unsubstd. phenyl group and halogen atom, such as chlorine or bromine.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-linear optical material comprising a benzooxozole compound useful for electro-optical elements, wavelength converting elements, optical switching elements and the like.

[0002]

2. Description of the Related Art In recent years, materials having a non-linear optical effect-a phenomenon in which when intense laser light is incident on a substance, emitted light having a component different from that of the incident light is obtained due to the interaction thereof-has attracted attention. .. Such materials are generally known as nonlinear optical materials and are described in detail in, for example, the following. "Nonlinier Optic
al Properties of Organic
and Polymeric Materials "A
CS SYMPOSIUM SERIES 233, D
avid J. Edited by Williams (America
n Chemical Society, 1983), "Organic Nonlinear Optical Materials" edited by Masao Kato, Hachiro Nakanishi (CMC, 1983), "Organic Electronics Materials" edited by Akio Taniguchi (Science Forum, 1986).

Non-linear optical materials include second harmonic generation (hereinafter referred to as SHG) and third harmonic generation (hereinafter referred to as THG).
It is an optical material used in active optical devices such as wavelength conversion, optical switch, phase conjugate wave generation, etc., and is expected to play a central role in the future optical information processing field.

Hitherto, as non-linear optical materials, potassium dihydrogen phosphate (KDP) and lithium niobate (Li) have been used.
Inorganic crystals such as NbO ₃ ) have been put to practical use.
Urea, 4-nitroaniline (p-NA), 2-methyl-
Organic crystals such as 4-nitroaniline (MNA) are also known. I / E / E Spectrum (IEE
E Spectrum) June (1981) No. 26
According to the description on page 33, an organic crystal generally has a larger nonlinear optical effect than an inorganic crystal, and SHG and THG
And the like, and the optical response speed is 10 as well.
It is considered to be about 00 times shorter, and it is recognized that the threshold value for optical damage is also large. Further, it is known that SHG does not appear in a single crystal having a symmetry center as a feature of the even-order nonlinear optical effect.

Generally, in the case of a nonlinear organic material, each molecule exhibits a nonlinear optical response, and its molecular hyperpolarizability: β
(Molecular hyperpolarizab
(depending on the size of the ionicity), even if a high quadratic nonlinear performance is exhibited in the molecular state as represented by 4-nitroaniline (p-NA) (that is, it has a large β), When crystallized, many molecules do not exhibit a quadratic nonlinear optical effect in the crystalline state because of the molecular symmetry. In addition, a methyl group was introduced into the ortho position of this p-NA to improve the molecular performance (ie β
Although the MNA that succeeded in breaking the crystal symmetry without decreasing the (size of B) has a large SHG tensor d ₁₁ , {B. F. Levine, et al, j. App
l. Phys. 50, 2523 (1970)}, it is difficult to effectively use the phase matching condition for efficiently extracting SHG. Further, MNA is difficult to obtain a large single crystal, and there are many problems in applying it as a device.

In addition, high-performance molecules are dispersed in a polymer,
Poling by electrolysis (Japanese Patent Laid-Open No. 61-18694)
Methods such as 2) have also been considered, but good results have not always been obtained.

On the other hand, among the nonlinear organic materials, there is not much search for materials exhibiting the third-order nonlinear optical effect expected for optical signal processing such as optical bistable. That is, although the third-order nonlinear optical property is an attribute of all organic materials, polydiacetylene compounds are the only materials that can be considered for practical use as optical elements.

[0008]

SUMMARY OF THE INVENTION In view of such circumstances, it is an object of the present invention to provide a non-linear optical material made of a compound exhibiting a high non-linear optical effect.

[0009]

Means for Solving the Problems The inventors of the present invention have conducted extensive research in order to solve the above problems, but have found that it is effective to use a specific benzoxazole compound as a nonlinear optical material. The present invention has been reached.

That is, the present invention is a non-linear optical material characterized by comprising a benzoxazole compound represented by the following general formula (I).

[0011]

[Chemical 2]

(Wherein R represents a hydrogen atom, an alkyl group, a halogen atom, a substituted or unsubstituted phenyl group, or a nitro group, Ar represents a substituted or unsubstituted aromatic group, and n represents 0, 1 or 2. ) As the aromatic group in the above general formula (I) of the present invention, a phenyl group, naphthalene,
Polycyclic aromatic compounds such as anthracene and pyrene, the substituent of the aromatic group, a substituted amino group, a hydroxy group, a substituted or unsubstituted alkoxy group, a substituted or unsubstituted alkyl group, a substituted or unsubstituted phenyl group And halogen atoms such as chlorine and bromine.

Specific examples of the benzoxazole compound represented by formula (I) of the present invention are shown in Table 1 below, but the scope of the present invention is not limited to these.

[0014]

[Table 1]

[0015]

[Table 2]

[0016]

[Table 3]

[0017]

[Table 4]

[0018]

[Table 5]

[0019]

[Table 6]

[0020]

[Table 7]

[0021]

[Table 8]

[0022]

[Table 9]

[0023]

[Table 10]

[0024]

[Table 11]

[0025]

[Table 12]

[0026]

[Table 13]

[0027]

[Table 14]

[0028]

[Table 15]

[0029]

[Table 16]

[0030]

[Table 17]

[0031]

[Table 18]

These compounds of the general formula (I) are generally prepared by using an o-aminophenol compound of the following general formula (II) and a carboxylic acid compound of the general formula (III) or an aldehyde compound of the general formula (IV). can do. As the acidic catalyst, p-toluenesulfonic acid, polyphosphoric acid,
Alternatively, sulfuric acid or the like is used, and a solvent is used if necessary, and as the solvent, toluene, xylene, tetrahydrofuran, methylene chloride, 1,2-dichloroethane, ethanol or the like is used. The reaction temperature is room temperature to 150 ° C, preferably 80 to 120 ° C. The ratio of the compound of general formula (II) to the compound of general formula (III) or general formula (IV) may be stoichiometric.

[0033]

[Chemical 3]

Ar- (CH = CH) nCOOH (II
I) Ar- (CH = CH) _n- CHO (IV)

[0035]

The present invention will be described in more detail based on the following examples, but the invention is not intended to be limited to these examples.

Example 1 Method for producing 2- (p-dimethylaminobenzene) benzoxazole: 4.5 g (0.03 mol) of p-dimethylaminobenzaldehyde was dissolved in 150 ml of ethanol to obtain 3.3 g (0%) of o-aminophenol. .03m
ol) is added and the mixture is refluxed for 5 hours. After allowing to cool, the precipitated crystals were separated by filtration, dissolved in 300 ml of tetrahydrofuran, and 6.7 g (0.0%) of dicyanodichlorobenzoquinone.
(3 mol) is added, and the mixture is reacted at room temperature with stirring. After the reaction was completed, 200 ml of ice water and 200 m of toluene were added to this.
l was added and stirred well, and the separated toluene layer was washed with water,
Dry over anhydrous magnesium sulfate. The residue obtained by distilling off toluene was recrystallized from diisopropyl ether to obtain 2.0 g of a pure target product.

Melting point: 177 to 178 ° C. The infrared absorption spectrum of this product is shown in FIG.

Example 2 Method for producing 2- (p-dimethylamino) styrylbenzoxazole A pure target product was obtained in the same manner as in Example 1.

Table 2 shows melting points and elemental analysis results of the compounds obtained as described above.

[0040]

[Table 19]

[0041]

[Example of use] The nonlinear optical performance of the compound was measured.

A second harmonic generation (SHG) measurement, which is a typical second-order nonlinear optical effect, is measured by S. K. Kurtz and T.M. T. Perry is J. Appl. Phys. 39,
3798 (1968).
This method is a method of irradiating the compound powder to be measured with a strong laser beam and measuring the intensity of the generated SHG with respect to the reference material, and it is possible to estimate the approximate second-order nonlinear performance.

As a light source, the present inventors have developed a high-power N
d: YAG laser (250 mJ / pulse, pulse width ~
20 ns) was used. (The oscillation wavelength of the Nd: YAG laser is 1.064 μm, and when this light is applied to the SHG active material, green SHG of 532 nm is obtained.)
Since the SHG from the sample filled in the quartz glass is scattered and observed in both the forward and backward directions with respect to the laser light traveling direction, the SHG intensity was measured in both the forward and backward directions. The results are shown in Table 3. The detector at this time was a photomultiplier tube, the infrared absorption filter cut the laser light, and the interference filter took out only SHG of 532 nm.

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

[0045]

[Table 20]

(* ADP: ammonium dihydrogen phosphate)
As is clear from Table 3, the compound of the present invention is effective as a non-linear optical material, and for example, it is used as an SHG element as shown in FIG. 1 by single crystallizing this material.

[0047]

As described above, the azo compound of the present invention is useful as a novel high performance nonlinear optical material.

[Brief description of drawings]

FIG. 1 is a diagram schematically showing an example of an SHG element using the nonlinear optical material of the present invention,

2 is an infrared absorption spectrum diagram of the material of the present invention synthesized in Example 1, FIG.

3 is an infrared absorption spectrum diagram of the material of the present invention synthesized in Example 2. FIG.

[Explanation of symbols]

 1 semiconductor laser 2 single crystal of the present invention

Claims (1)

[Claims] 1. A non-linear optical material comprising a benzoxazole compound represented by the following general formula (I): (However, R is a hydrogen atom, an alkyl group, a halogen atom,
Substituted or unsubstituted phenyl group, or nitro group, Ar is a substituted or unsubstituted aromatic group, and n is 0 or 1. )