JPH04345140A - Nonlinear optical material and optical function element formed by using this material - Google Patents

Abstract

PURPOSE:To improve nonlinear performance and to expand transparency from a visible region to a near UV region by forming hexahydro-1,3,5-tribenzoyl-s- triazine consisting of the triazine deriv. expressed by specific formula. CONSTITUTION:The nonlinear optical material is constituted of the triazine compd. expressed by the formula I. In the formula I, R1 to R3 denote an arom. ring, hetero ring, org. group having a conjugation group which may be different from each other or may be substd. X1 to X3 denote a hydrogen atom, halogen atom or org. residual group which may be different from each other; (n), (m), (l) denote integer 0 to 5. The org. nonlinear material obtd. in such a manner consists of the compd. having the triazine ring at the molecular center and, therefore, has the crystal structure asymmetrical to the center line indispensable in the generation of the second harmonic wave of light which is one of the org. nonlinear optical characteristics. The nonlinear optical element consisting of the medium which allows easy crystal formation and has excellent thermal stability if thus obtd. Then, the groups having the high dipole moment do not exist in the molecules.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a nonlinear optical material made of an organic compound and an optical functional element using the same.

0002

2. Description of the Related Art Nonlinear optical elements are attracting attention as wavelength conversion elements that utilize second-order and third-order optical harmonic generation, optical mixing, or optical parametric oscillation. It is also attracting attention as a basic element of optical computers, such as optical bistable devices used as optical switches.

Conventionally, lithium niobate (LiNbO3), gallium arsenide (GaAs) have been used as nonlinear optical materials.
) and other inorganic materials have been studied. However, in recent years, compared to the above materials, the nonlinear optical performance has been significantly higher (10~
100 times), and nonlinear optical materials made of organic compounds with high optical response speeds, which are important in optical bistable devices, have begun to be studied.

Nonlinear optical materials made of organic compounds include urea, 2-methyl-4-nitroaniline (abbreviated as MNA),
: JP-A-55-500960), N-(4-nitrophenyl)-L-prolinol (abbreviation NPP: JP-A-59-21665), and the like have been proposed. especially,
MNA and NPP are known to have a second-order nonlinear optical effect that is 100 times or more greater than that of inorganic materials.

[0005]

[Problems to be Solved by the Invention] However, although conventional nonlinear optical materials made of organic compounds have very large nonlinear optical constants, they have problems such as difficulty in obtaining large single crystals, poor stability of the crystals, and poor light transmission. There were problems such as the long cutoff wavelength (light absorption is in the visible range). especially,
The fact that the cutoff wavelength is long is an important issue that should be improved, for example, in application to optical second harmonic generation (SHG) wavelength conversion elements of semiconductor lasers. This point is
The same requirement applies not only to HG wavelength conversion elements but also to a wide range of optical processing in the visible range.

[0006] The cutoff wavelength of MNA is 480 nm,
NPP is in the long wavelength range of about 490 nm. Therefore, it is not preferable as a material for the SHG wavelength conversion element of the current GaAlAs-based near-infrared semiconductor laser (oscillation wavelength of about 800 to 900 nm).

An object of the present invention is to provide a nonlinear optical material made of a stable organic compound that has a large nonlinear optical constant and a short cutoff wavelength.

Another object of the present invention is to provide an optical functional element using the above nonlinear optical material.

[0009]

[Means for Solving the Problems] The gist of the present invention for solving the above problems is as follows.

General formula [1]

[0011]

[Chemical formula 3]

[In the formula, R1, R2, and R3 represent an organic group having an aromatic ring, a heterocycle, or a conjugated system, and these may be different from each other or substituted, and X1,
3 represents a hydrogen atom, a halogen atom, or an organic residue, and these may be different from each other. n, m, and l represent integers of 0 to 5. ] A nonlinear optical material characterized by being composed of a triazine compound represented by the following.

In particular, in general formula [1], R1, R2
, R3 is an aromatic ring group such as a phenyl group, a naphthyl group, an anthryl group, a biphenylyl group, a styryl group, a phenanthryl group, a furyl group, a pyrrolyl group, a pyridyl group, a quinolyl group, a thienyl group, a furfuryl group, a thenyl group, a piperidino group, It is an organic group such as a heterocyclic group such as a piperidinyl group, an alkyl group, or an alkenyl group, and in particular, the following structural formula [2
] Preferably, a nonlinear optical material selected from the organic group represented by the following is used.

[0014]

[C4]

Furthermore, in the general formula [1], X1,
X2 and X3 are organic residues, particularly an alkyl group, an alkoxyl group, a nitro group, a nitrile group, an alkylamino group, a dialkylamino group, a carbamoyl group, a hydroxyl group, a mercapto group, a carboxyl ester group, a chlorine atom, a bromine atom, an iodine atom , trialkylsilyl groups are preferred.

The method for synthesizing the above triazine compound is as follows:
For example, the Journal of American Chemical Society
rican Chemical Society)
, Vol. 70, pp. 8079-3081 (1948), Synthesis, pp. 467-468 (1948).
976).

The nonlinear optical material of the present invention can be used alone in a crystalline or amorphous state and in the form of a lump, a plate, a fiber, a powder, or a thin film. Further, in the above shape, different materials or other materials having different structures according to the present invention can coexist or be used in a mixed manner. In particular, specific examples of these applications include optical waveguides, optical cables, integrated circuits, display elements, and the like.

Examples of compounds that can be used as the nonlinear optical material of the present invention are shown below. In addition, in the following formula, Me represents a methyl group.

[0019]

[C5]

[0020]

[C6]

[0021]

[C7]

[0022]

[Chemical formula 8]

When the nonlinear optical material of the present invention is used in a crystalline state, known methods can be used to form the crystal. Examples include the Bridgman method, the temperature drop method, the solvent evaporation method, and the solvent composition change method. Note that the triazine compound represented by the general formula [1] desirably has a non-centrosymmetric crystal structure.

Furthermore, other materials that can coexist or coexist include inorganic substances such as glass, crystal,
Diamond, silicon dioxide, mica, marble, calcite,
Single crystal silicon, amorphous silicon, GaP, CdS, K
DP, KTP, lithium niobate, potassium bromide, Rochelle salt, copper sulfate, calcium fluoride, graphite,
Tin dioxide, barium titanate, red blood salt, china, ceramics, bentonite, cement, etc., metals, or alloys can be used. Examples of organic substances include polycarbonate, polysulfone, polyarylate, polyester, polyamide, polyimide, polysiloxane, polyethylene terephthalate, polyvinyl acetate, polyethylene, polypropylene, acrylic resin, polybutadiene, polyvinyl chloride, polyvinylidene chloride, petroleum resin, and melamine. Resins, epoxy resins, phenolic resins, isoprene rubber, ethylene-propylene rubber, norbornene resins, cyanoacrylate resins, styrene resins and copolymers of these resins, or polysaccharides such as cellulose, starch, chitin, and lignin, collagen, Glue, gelatin, agar, silk thread, cotton thread, nylon thread, albumin, globulin and other proteins, wood, bone powder, etc.; low-molecular organic substances include condensed aromatic compounds such as naphthalene and anthracene, dyes, pigments, urea, and tartaric acid. , optically active amino acids, and the like.

[0025] The nonlinear optical material may be used for various purposes such as adhesion, fusion, electrodeposition, vapor deposition, pressure bonding, sputtering, MBE method, dyeing, melt molding, kneading, press molding, coating from a solution, etc. It can be formed by various methods depending on the situation.

[0026] After forming a product using the nonlinear optical material of the present invention, post-treatment may be performed to improve appearance and properties and extend life. These post-treatments include thermal annealing,
Examples include, but are not limited to, radiation irradiation, electron beam irradiation, light irradiation, radio wave irradiation, magnetic force line irradiation, ultrasound irradiation, and the like.

The nonlinear optical material of the present invention contains N in a powder state.
By irradiating d-YAG laser light (wavelength 1.06 μm), green light (wavelength 0.53 μm), which is the second harmonic of light, is emitted.
μm) can be generated.

Furthermore, a single crystal nonlinear optical material can generate a coherent optical second harmonic by injecting an Nd-YAG laser beam from a specific crystal plane. By holding it in a resonator, coherent optical second harmonics can be generated with high conversion efficiency.

[0029]By filling the space to be the core surrounded by the cladding layer with the nonlinear optical material and forming a single crystal, it is possible to generate optical second harmonics even with a low intensity of incident light. In this case, GaAlAs semiconductor laser light (
When a light source having a wavelength of 0.88 to 0.75 μm is used, a short-wavelength solid-state laser that emits blue light (wavelength of 0.44 to 0.37 μm) can be formed. The cladding and core can be formed either in the shape of a fiber or in the shape of a waveguide.

The nonlinear optical material of the present invention is used in devices that utilize various nonlinear optical effects, particularly nonlinear optical elements characterized by even-order nonlinear susceptibility including second-order nonlinearity. Furthermore, by using the organic nonlinear optical element of the present invention, it is possible to realize a resonator type optical second harmonic generation element with high laser resistance and a Cherenkov type optical second harmonic generation element that is compact and has high power density. .

Specific applications include nonlinear optical elements using organic materials as a medium with excellent nonlinear optical effects such as optical mixing, optical parametric oscillation, optical harmonic generation, Pockels effect, and Kerr effect, and in particular, optical wavelength conversion. It can be applied to optical functional devices such as devices, optical modulators, optical switches, optical memories, optical mixers, optical phase separators, optical phase conjugate mirrors, optical waveguides, and optical logic circuits.

[0032]

[Operation] Since the organic nonlinear material of the present invention is composed of a compound containing a structure having a triazine ring at the center of the molecule, it exhibits non-centrosymmetric properties, which are essential for optical second harmonic generation, which is one of the organic nonlinear optical properties. The present invention provides a nonlinear optical element made of a medium that has a crystal structure, is easy to prepare as a crystal, and has excellent thermal stability. Therefore, since there is no substance with a large dipole moment in the molecule, the cutoff wavelength does not extend into the visible range, and crystals with inversion symmetry are not formed.

[0033]

EXAMPLES Next, the present invention will be explained based on examples.

[Example 1] Hexahydro-1,3,5-tribenzoyl used in the organic nonlinear material of the present invention
A method for synthesizing s-triazine will be described.

11 g of benzonitrile (
0.2 mol) and 0.4 g of concentrated sulfuric acid were added, and a thermometer, mercury sealed stirrer, dropping funnel and cooling pipe were attached. The mixture was heated to 95°C, and while refluxing, trioxane 6
g (0.2 mol as formaldehyde) was added dropwise. The temperature inside the reaction system rose as the dropwise addition was completed, and heating was continued until the temperature reached 155° C., at which reflux stopped after the dropwise addition was completed. After cooling, the obtained dark brown solid was thoroughly washed with 90% ethyl alcohol, and the white solid was reprecipitated and recrystallized from a chloroform solution/ether system to obtain the desired product as white crystals. Yield: 10 g, yield: 37.5%, melting point: 220-222°C. The result of elemental analysis is N: 10.38 (calculated value 10.53
).

[Example 2] Optical second harmonic generation (SHG), which is one of the nonlinear optical properties of hexahydro-1,3,5-tribenzoyl-s-triazine obtained in Example 1,
) and transparency were measured.

The above compound was dissolved in 98% ethanol heated to 70°C to make a saturated solution, and the temperature was increased from 70°C to -1
It was slowly cooled to 0°C at a rate of -0.23°C/h over about two weeks to obtain a plurality of colorless single crystals measuring 10 x 5 x 5 mm to several hundred μm square. Next, among these single crystals, relatively small single crystals of 1 mm square or less are collected, crushed in an agate pot, and passed through a sieve with a controlled particle size of 100 to 300 μm.
The powder was collected and pressed into a pellet to form a sample. As shown in FIG. 1, the sample 3 was attached to a non-fluorescent slide glass substrate 2, and a Nd-YAG laser beam 10 (manufactured by Kantaray Co., Ltd., DCR-3, wavelength 1.06 μm, peak power 0.1 MW, repetition frequency 10 Hz) was applied. ), a second harmonic of green light was observed.

FIG. 1 is a schematic diagram of the above optical system.
-Q-switch Nd-Y which is a light emitting device of YAG laser
The AG laser 1 irradiates the center of the sample 3 with incident light 10 . The resulting diffusely reflected light 12 was transmitted through a lens 5 and an infrared cut filter 6, and the intensity of the second harmonic of the light was measured using a monochromator 7 and a phototube 8.

It can be seen that the intensity of the second harmonic of the light is 8.6 times that of the case where urea powder is similarly irradiated with laser light, and the nonlinear optical constant is large.

Next, a part of the powder was dissolved to a concentration of 9.
．． An isopropyl alcohol solution of 012×10−6 mol/l was prepared, and the absorption spectrum at a wavelength of 200 to 850 nm was measured using a spectrometer (manufactured by Hitachi, Ltd., model 340 self-recording spectrophotometer). The results are shown in FIG.

[0041]λmax220.3nm (ε=21605
), cutoff (λcut off) wavelength 298nm
Met.

FIG. 3 shows a schematic diagram of an optical wavelength conversion device which is an application example of the optical functional element made of the organic nonlinear material of the present invention.

A laser beam 26 (GaAlAs semiconductor laser beam; wavelength 0
．． Blue light (wavelength: 0.44-0.37 μm) is transmitted through the collimator 22, anamorphic prism 23, and condensing lens 24.
) can be obtained. By using the SHG element 25, an optical wavelength conversion device with a short cutoff wavelength and excellent laser beam resistance can be obtained.

[0044]

According to the present invention, a nonlinear optical material having a short cutoff wavelength and a large nonlinear optical constant can be obtained. By using this material, it is possible to provide an optical functional element with unprecedented nonlinear optical properties.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of an optical system used in an example of the present invention to measure optical second harmonics.

[Figure 2] Hexahydro-1,3 used in Examples of the present invention
, 5-tribenzoyl-s-triazine in isopropyl alcohol.

FIG. 3 is a schematic diagram of an optical wavelength conversion device using an optical functional element made of an organic nonlinear material of the present invention.

[Explanation of symbols]

1...Q-switch Nd-YAG laser, 2...substrate, 3...
Sample, 4... Damper, 5... Lens, 6... Infrared cut filter, 7... Monochromator, 8... Photomultiplier tube, 9... Pen recorder, 10... Incident light (wavelength 1.06 μm), 11
...Reflected light (wavelength 1.06, 0.53 μm), 12...Scattered light (wavelength 1.06, 0.53 μm), 21...Laser diode, 22...Collimator, 23...Anamorphic prism, 24...Condensing lens , 25...SHG element, 26
...laser light.

Claims (5)

[Claims] [Claim 1] General formula [1] [Formula 1] [In the formula, R1, R2, and R3 represent an organic group having an aromatic ring, a heterocycle, or a conjugated system, and these may be different from each other or substituted. X1, X2, and X3 often represent a hydrogen atom, a halogen atom, or an organic residue, and these may be different from each other. n, m, and l represent integers of 0 to 5. ] A nonlinear optical material characterized by being composed of a triazine compound represented by the following. [Claim 2] In the general formula [1], R1, R2,
2. The nonlinear optical material according to claim 1, wherein R3 is selected from an organic group represented by the structural formula [2]. [Chemical 2] [Claim 3] In the general formula [1], X1, X2,
Claim 1 or 2, wherein X3 is selected from a hydrogen atom, an alkyl group, an alkoxyl group, a nitro group, a dialkylamino group, a hydroxyl group, an ester group, a chlorine atom, a bromine atom, an iodine atom, and a trialkylsilyl group. Nonlinear optical materials described in . 4. The nonlinear optical material according to claim 1, wherein the triazine compound represented by the general formula [1] has a non-centrosymmetric crystal structure. 5. An optical functional element characterized by using the nonlinear optical material according to any one of claims 1 to 4.