JPH05127202A - Nonlinear optical material and optical function type element formed by using this material - Google Patents

Abstract

PURPOSE:To obtain the org. nonlinear optical element for which a material having a short cutoff wavelength and a large nonlinear optical constant is used by using a specific kynucridine compd. as a nonlinear optical medium. CONSTITUTION:The kynucridine compd. expressed by formula I is used as the nonlinear optical medium of the nonlinear optical element contg. the nonlinear optical medium having a light incident surface and a light exit surface. In the formula I, at least one among R1 to R7 denote an arom. ring, heterocycle or org. group having a conjugation system and the rest denote a hydrogen atom, halogen atom or org. residue which may be different from each other or substd. Particularly at least one among R1 to R7 consist preferably of an optically active group. As a result, the nonlinear optical element for which the stable org. nonlinear optical material having the large nonlinear optical constant and short cutoff wavelength is used is obtd.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a nonlinear optical element using an organic material excellent in nonlinear optical effect such as optical mixing, optical parametric oscillation, optical harmonic generation, Pockels effect, Kerr effect, etc. The present invention relates to optical elements such as optical wavelength conversion elements, optical modulators, optical switches, and optical memories.

[0002]

2. Description of the Related Art Non-linear optical elements have been attracting attention as wavelength conversion elements utilizing second-order and third-order optical harmonic generation, optical mixing, or optical parametric oscillation. In addition, it is attracting attention as a basic element of an optical computer that is expected to be realized in the future, such as an optical bistable element as an optical switch.

Conventionally, inorganic materials such as lithium niobate (LiNbO ₃ ) and gallium arsenide (GaAs) have been studied in detail as nonlinear optical materials. However, in recent years, compared with these materials, organic nonlinear optical materials with significantly higher nonlinear optical performance (10 to 100 times) and very high optical response speed, which is important for optical bistable elements, are being studied. Became.

These organic nonlinear optical materials include urea,
2-Methyl-4-nitroaniline (name MNA) (JP-A-55-500960), N- (4-nitrophenyl)-
L-Prolinol (abbreviation NPP) (Japanese Patent Laid-Open No. 59-21665) and the like have been proposed. In particular, MNA and NPP
It is known to have a second-order nonlinear optical effect, which is more than 100 times that of inorganic materials.

[0005]

The above-mentioned conventional organic nonlinear optical material has a very large nonlinear optical constant, but on the other hand, it is difficult to obtain a large single crystal, the stability of the crystal is poor, and light transmittance is exhibited. There is a problem in that the cutoff wavelength is long, that is, the light absorption is in the visible region. In particular, the problem that the cutoff wavelength is long is considered to be a problem to be improved in practical use such as application to an optical second harmonic generation (SHG) wavelength conversion element. The same applies not only to the SHG wavelength conversion element, but also to a wide range of optical processing in the visible range. M
In NA, the cutoff wavelength is 480 nm, and in NPP, it is about 490 nm. Therefore,
Near-infrared semiconductor laser currently used (oscillation wavelength about 8
It is considered to be unsuitable as a material for the SHG wavelength conversion element of 100 to 900 nm). Furthermore, red semiconductor lasers (oscillation wavelengths of about 600 to 800 n
m) Most of the organic nonlinear optical materials known today as materials for the corresponding SHG wavelength conversion element cannot be used because of their long cutoff wavelengths.

When developing such an organic nonlinear optical material having excellent transparency, the molecular design policy is to improve nonlinearity per molecule and transparency, and at the same time control the molecular orientation in the crystalline state. It becomes important.

Of these, the second-order nonlinear polarizability β per molecule is given by Equation 1 according to the two-level model in which only the ground state and the excited state having the largest contribution are considered. (Reference: For example, Masahiro Umegaki "Organic Nonlinear Optical Materials"
See Bushin Publishing (1990). )

[0008]

[Equation 1]

Where e is elementary charge, h is Planck's constant, Δre is difference between permanent dipole moments of ground state and excited state, rge is transition moment from ground state to excited state, and ωeg is ground state and excited state. , And ω is the frequency of the incident light. To increase this β, Δr
It is necessary to increase e and reg and decrease ωeg. For that reason, a molecule in which the electron distribution in the molecule in the ground state and the excited state largely changes is preferable. That is, the larger the intramolecular charge mobility, the greater the non-linearity per molecule. However, the longest absorption spectrum showing the transparency of a molecule has a peak at ωeg and its relaxation intensity is shown in an amount depending on reg. Therefore, even if ωeg is made small and reg is made large, the absorption edge becomes long, and Transparency is reduced. In other words, there is a trade-off relationship between non-linearity per molecule and transparency, and there is a limit to improving the characteristics only by designing the molecular structure.

On the other hand, the nonlinear constant of the crystal state depends on the orientation state and density of the molecules in the unit cell of the crystal. In the case of adopting the centrosymmetric orientation state, no matter how large the non-linearity per molecule is, the non-linearity cannot be exhibited as a crystal, and it is necessary to form the crystal structure in the other orientation states.
However, it is not currently possible to theoretically predict the crystal structure in advance, and it is necessary to actually synthesize a new compound and measure the non-linearity with a single crystal. For this reason, there is a demand for a design guideline for a molecule that tends to have a crystal structure that can surely utilize the non-linearity per molecule even in a crystalline state.

An object of the present invention is to provide a nonlinear optical element using a stable organic nonlinear optical material having a large nonlinear optical constant and a short cutoff wavelength.

[0012]

The gist of the present invention for solving the above problems is as follows.

[0013]

[Chemical 3]

(In the formula, at least one of R _{1 to} R _{7 represents} an aromatic ring, a hetero ring, or an organic group having a conjugated system, and the other represents a hydrogen atom, a halogen atom, or an organic residue, and These may be different from each other or may be substituted.) In the non-linear optical material, the quinuclidine compound represented by the formula (1) is used.

In particular, in the general formula (1), it is preferable that at least one of R _{1 to} R ₇ is an optically active group, which is the nonlinear optical material described in (1). In particular, as such an optically active group, structural formula (2)

[0016]

[Chemical 4]

[0017] (wherein, R _'1 ~R' ₃ represents a different substituent from each other selected from the group consisting of a hydrogen atom, a halogen atom or an organic residue,, C * indicates an optically active carbon. It is preferable that the nonlinear optical material according to (1) is composed of an organic group represented by (4). The method for synthesizing the quinuclidine-based compound is described in, for example, Beilstein Vol.
It is described on pages 02, 506, 511, etc.

The non-linear optical material of the present invention can be used by being formed into a lump, a plate, a fiber, a powder or a thin film in a crystalline or non-crystalline state as a simple substance. Further, in the above-mentioned shape, it is possible to coexist and coexist with a different material or another material having a different structure of the present invention.
In particular, specific application examples of these include optical waveguides, optical cables, optical integrated circuits, and display devices.

When the nonlinear optical material of the present invention is used in a crystalline state, a known method can be used for forming the crystal.
For example, there are the Bridgman method, the temperature drop method, the solvent evaporation method, the solvent composition change method, and the like.

Other materials that can coexist and coexist are inorganic substances such as glass, quartz, diamond, silicon dioxide, mica, marble, calcite, single crystal silicon, amorphous silicon, GaP, CdS. , KDP, KT
P, lithium niobate, charismum bromide, Rochelle salt,
Copper sulfate, calcium fluoride, graphite, tin dioxide,
Barium titanate, red blood salt, ceramics, ceramics, bentonite, cement, etc. or metal or alloy 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, Melamine resin, epoxy resin, phenol resin, isoprene rubber, ethylene-propylene rubber, norbornene resin, cyanoacrylate resin, styrene resin and copolymers of these resins,
Alternatively, cellulose, starch, chitin, agar, silk thread, cotton thread, nylon thread, albumin, globulin and other proteins, wood, bone meal, etc., low molecular weight organic substances such as naphthalene,
Examples thereof include condensed aromatic compounds such as anthracene, dyes, pigments, urea, tartaric acid, and optically active amino acids.

The non-linear optical material may be adhered, fused, electro-deposited, vapor-deposited, pressure-bonded, sputtered, MBE method, dyed, melt-molded, kneaded, press-molded, coated from a solution, etc. depending on its use or purpose. Can be formed by various methods.

After forming a product using the non-linear optical material of the present invention, a treatment for improving the appearance and characteristics and extending the life may be performed. Examples of such a post-treatment include, but are not limited to, thermal annealing radiation irradiation, electron beam irradiation, light irradiation, radio wave irradiation, magnetic force line irradiation, and ultrasonic wave irradiation.

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

Further, the single crystal nonlinear optical material can generate a coherent optical second harmonic by injecting the Nd-YAG laser light from a specific crystal plane, and such a crystal can be used as a laser light source. By holding it in the resonator, it is possible to generate an optical second harmonic with high conversion efficiency and coherence.

By filling a non-linear optical material in a space to be a core surrounded by a cladding layer to form a single crystal,
It is possible to generate an optical second harmonic even with a small incident light intensity. In this case, GaAlAs semiconductor laser (wavelength 0.88
~ 0.75μm) as a light source, blue light (wavelength 0.44)
It is possible to form a short-wavelength solid-state laser that oscillates up to 0.37 μm. The cladding and core can be formed in either fiber or waveguide configurations.

The non-linear optical material of the present invention is used for devices utilizing various non-linear optical effects, particularly non-linear optics characterized by even-order non-linear susceptibility including second-order non-linearity. Further, by using the organic nonlinear optical element of the present invention, it is possible to realize a resonator type optical second harmonic generation element having high laser light resistance and a compact Cherenkov type optical second harmonic generation element having high power density.

A specific application is a nonlinear optical element using an organic material excellent in nonlinear optical effect such as light mixing, optical parametric oscillation, optical harmonic generation, Pockels effect, Kerr effect, etc. , Optical modulator, optical switch, optical memory, optical mixer, optical phase classifier, optical phase conjugate mirror, optical waveguide, optical functional element such as optical logic circuit.

[0028]

According to the present invention, as in a nonlinear optical element using a conventional organic nonlinear optical material, a crystal having a cutoff wavelength in the visible region or an inversion symmetry due to a large dipole moment in a molecule. The problem that the tendency to form is strong is solved. In addition, since the medium is composed of a compound containing a structure having a quinuclidine skeleton at the molecular center, crystallization is specifically performed at the skeleton portion, and since it has an optically active skeleton, it is one of the organic nonlinear optical properties. It is possible to provide a non-linear optical element composed of a medium having a non-centrosymmetric crystal structure, which is indispensable for the generation of a certain optical second harmonic, and which is easily crystallized and has high thermal stability. In addition, by using a nonlinear optical element made of a medium having such characteristics, a resonator-type optical second-harmonic generation element that requires high laser light resistance and a compact, high-density Cherenkov-type second-harmonic element are especially used. A wave generating element can be realized.

[0029]

EXAMPLES Examples of the organic nonlinear optical element according to the present invention will be described below.

Example 1 First, it is one of the derivatives of the compound quinuclidine represented by the above structural formula (1).

[0031]

[Chemical 5]

The results of confirming the optical second harmonic generation (SHG) and the transparency of quinidine represented by are reported below.

98% of commercially available quinidine (manufactured by Tokyo Kasei, optical purity (α) = + 263 ° (c = 1, C ₂ H ₅ OH))
Dissolve in ethanol at 70 ° C to give a saturated solution,
The temperature is gradually cooled from 70 ° C. to −10 ° C. at a rate of −0.23 ° C./hour for about 2 weeks and then 10 × 5 × 5 mm to several hundred μ
A plurality of colorless and transparent single crystals of m-square were obtained.

Next, among these single crystals, relatively small single crystals having a size of 1 mm square or less are collected and crushed in an agate bowl, and powder having a particle size of 100 μm to 300 μm is collected in the form of pellets. Compacted into. This pellet was attached to a non-fluorescent slide glass, and a Q-switched Nd-YAG laser beam (DCR-produced by Kantaray Co., Ltd.) was attached to the center thereof.
3, a wavelength of 1.06 μm, a peak power of 0.1 MW, and a repetition frequency of 10 Hz) were observed, and a green light second harmonic was observed. The intensity was 16.7 times as high as when the urea laser was irradiated with the same laser beam.

Next, a part of this powder was dissolved in ethanol to obtain a solution having a concentration of 1.0 × 10 ^-5 mol / liter,
An absorption spectrum was measured in a wavelength range of 200 to 850 nm using a spectroscope (Hitachi 340 type self-recording spectrophotometer). As a result, it was found that λ _max = 332 nm and the cutoff wavelength was 355 nm.

Comparative Example 1 Next, for comparison, the optical second harmonic generation of a quinoline compound similar to structural formula (3) and containing no quinuclidine skeleton, quinoline, 2-hydroxyquinoline, and 4-hydroxyquinoline ( SHG) and the results of confirming transparency will be reported. These quinoline-based compounds are described, for example, in the literature (JP-A-1-2299234 and JP-A-2299234).
2-262627), a quinoline-based compound containing no quinuclidine skeleton, 5-amino-6-nitroquinoline, 6-nitroquinoline, 5-nitroquinoline, 8-quinolinol, 6-aminoquinoline, 6 -Cyanoquinoline, 2- (N-prolinol) -8-nitroquinoline,
In combination with the literature value of the intensity of the photo second harmonic generation (SHG) of 2- (N-prolinol) -6-nitroquinoline, the quinidine shown in Example 1 does not impair its transparency and exhibits nonlinearity. Can be seen to have improved. The results are summarized in Table 1.

[0037]

[Table 1]

[0038]

According to the present invention, it is possible to obtain an organic nonlinear optical element using a material having a short cutoff wavelength and a large nonlinear optical constant.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of an optical system for confirming generation of an optical second harmonic used in an example of the present invention.

FIG. 2 is an absorption spectrum diagram of the compound quinidine used in the examples of the present invention in ethanol.

[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, 11 ... Reflected light, 12 ... Scattered light.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hiroshi Terao 4026 Kuji Town, Hitachi City, Hitachi, Ibaraki Prefecture Hitate Manufacturing Co., Ltd.Hitachi Research Laboratory (72) Inventor Atsushi Tsunoda 4026 Kuji Town, Hitachi City, Hitachi Ibaraki Co. Hitachi Research Laboratory

Claims (4)

[Claims] 1. A non-linear optical element including a non-linear optical medium having a light incident surface and a light emitting surface, wherein the non-linear optical medium is: (In the formula, at least one of R _{1 to} R _{7 represents} an aromatic ring, a hetero ring, or an organic group having a conjugated system, the other represents a hydrogen atom, a halogen atom, or an organic residue, and these are mutually A non-linear optical element, which is a quinuclidine compound represented by different or substituted). 2. The nonlinear optical material according to claim 1, wherein at least one of R _{1 to} R ₇ is an optically active group. 3. The structure according to claim 1, wherein at least one of R _{1 to} R ₇ has the structural formula: Shown by (wherein, R _'1 ~R' ₃ represents a different substituent from each other selected from the group consisting of a hydrogen atom, a halogen atom or an organic residue,, C * indicates an optically active carbon.) A nonlinear optical material consisting of an optically active group. 4. An optical functional element using the nonlinear optical material according to claim 1, 2.