JP2729673B2 - Novel organic nonlinear optical material and method of converting light wavelength using the same - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a nonlinear optical material suitable for use in various devices utilizing a nonlinear optical effect such as a wavelength conversion device. Further, the present invention relates to a method for converting a light wavelength using a nonlinear optical material.

(Prior Art) In recent years, a material having a nonlinear optical effect-nonlinearity between polarization and an electric field, which appears when a strong optical electric field such as laser light is applied-has attracted attention.

Such materials are generally known as non-linear optical materials and are described in detail, for example, in:
“Nonliner Optical Properties of Organic and Polym
eric Material "ACS SYMPOSIUMSERIES 233 David J. Will
iams (American Chemical Society, 1983),
"Organic Nonlinear Optical Materials", edited by Masao Kato and Hachiro Nakanishi (CMC, 1985).

One of the applications of the nonlinear optical material is a second harmonic generation (SHG) based on a second-order nonlinear effect and a wavelength conversion device using a sum frequency and a difference frequency. Until now, inorganic perovskites represented by lithium niobate have been practically used. However, in recent years, it has become known that a π-electron conjugated organic compound having an electron donating group and an electron withdrawing group has various properties as a nonlinear optical material, which greatly exceeds the above-mentioned inorganic substances.

Therefore, as an organic compound exhibiting a nonlinear optical response to be used for this material, a compound having a high nonlinear susceptibility in a molecular state is desirable.

However, to be useful as a second-order nonlinear optical material, performance in the molecular state alone is not sufficient, and it is essential that the molecular arrangement in the aggregated state has no inversion symmetry. However, at present, it is extremely difficult to predict the molecular arrangement, and the probability of existence in all organic compounds is not high.

(Problems to be Solved by the Invention) Accordingly, a first object of the present invention is to provide an organic nonlinear optical material exhibiting high nonlinear response. A second object is to provide a method that utilizes the response related to light wavelength conversion among the nonlinear responses.

(Means for Solving the Problems) As a result of intensive studies, the present inventors have found that a mesoionic compound or an acid adduct thereof, preferably a compound represented by the following general formula (I) or an acid adduct thereof is non-linearly converted. It has been found that the object of the present invention can be achieved by using the compound as an optically responsive compound.

General formula (I) (Wherein, X represents a chalcogen atom or N-R ^4.
R ¹ , R ² and R ³ represent a hydrogen atom, an alkyl group or an aryl group, and R ¹ and R ² may form a ring. R ⁴ represents an aryl group. The mesoionic compounds are a group of compounds represented by sydnone (a) . In addition to oxadiazole compounds such as sydnones, oxatriazole compounds, thiazole compounds, oxo-type mesoionic compounds such as dithiol compounds, sydnonimine compounds, thiazole compounds, dithiol compounds, and the like are known. , By Masaki Ota and Hiroshi Kato; The Chemical Journal of Japan, Vol. 86, No. 7, 661
See page 673.

Examples of the compound represented by the general formula (I) are shown below.

The synthesis of these compounds can be carried out with reference to the above-mentioned Ota et al.

As is clear from the examples described below, the nonlinear optical material of the present invention is particularly useful as a material for wavelength conversion. However, the application of the nonlinear optical material of the present invention is not limited to the wavelength conversion element, but can be used for any element utilizing the nonlinear optical effect. Specific examples of the device in which the nonlinear optical material of the present invention can be used include, in addition to the wavelength conversion device, optical bistable devices (optical storage device, optical pulse waveform control device, optical limiter, differential amplifier device, optical transistor, A / D Conversion element, optical logic element, optical multivibrator, optical flip-flop circuit, etc.),
An optical modulation element, a phase conjugate optical element, and the like can be given.

The compounds according to the invention can be used, for example, in the form of powder, in the form of inclusions of molecules in the host lattice (polymers, inclusion compounds, solid solutions, liquid crystals), in the form of thin layers deposited on supports (Langmea-Blodgett membranes). Etc.), a single crystal form, a solution form and the like can be used as a nonlinear optical material in various forms.

Further, the compound of the present invention can be used by binding to a polymer, polydiacetylene or the like in a pendant form.

Details of these methods are described in the above-mentioned work by DJ Williams.

(Examples) Next, the present invention will be described in detail based on examples.

Example 2nd harmonic generation measurement was performed by SKKu
rtz), TTPerry, Journal of Applied Physics (J. Appl. Phy)
s.) 39, p. 3798 (1968) was carried out on the powder of the compound of the present invention.

 The measurement was performed using the apparatus shown in FIG.

That is, the measurement was performed using pulsed YAG laser light (λ = 1.064).
μm, a beam diameter of ≒ 1 mmφ, and a peak power of ≒ 10 Mw / cm ² ) were used as fundamental waves, and the intensity of the second harmonic was measured by the evaluation apparatus shown in FIG. The measurement was performed by relative comparison with the intensity of the second harmonic of urea. When the intensity was low, visual observation was performed. In particular, in order to distinguish between the emission due to two-photon absorption of the fundamental wave (mainly yellow and red emission) and the second harmonic, a spectroscope was put in and only the second harmonic was measured. Further, the main purpose of the measurement by the powder method is to determine the presence or absence of nonlinearity of the substance, and the intensity ratio is a reference value of the magnitude of the specific linearity.

 The results are shown in Table 1.

(Effect of the Invention) A compound exhibiting SHG activity by these powder methods can be used as a wavelength conversion element by the following method.

1. The above compound is monocrystallized in the core of the fiber, and a wavelength conversion device using glass as a cladding material is prepared. The second harmonic can be generated by inputting a YAG laser beam. Further, as another method, similarly, a waveguide type wavelength conversion element can be prepared to generate the second harmonic. At this time, the Cherenkov radiation method was used as the phase matching method. However, it is not limited to these,
Waveguide-waveguide phase matching is also possible. Wavelength-converted waves are not limited to second harmonics, but are also used for third harmonic, sum and difference frequency generation.

2. Next, the above compound is converted into a single crystal, and a bulk single crystal is cut out from the compound, and a second harmonic can be generated by inputting a YAG laser beam. At this time, an angle phase matching was used as a phase matching method. The wavelength conversion efficiency can be increased by using these bulk single crystals not only outside the laser cavity but also inside a solid laser cavity such as an LD pumped solid laser. Furthermore, the wavelength conversion efficiency can be increased by arranging it in the resonator of the external resonator type LD.

For the above-mentioned single crystallization, a Bridgman method, a solvent evaporation method, or the like is used.

The wavelength-converted wave is used not only for the second harmonic, but also for the generation of the third harmonic and the sum difference frequency.

[Brief description of the drawings]

FIG. 1 shows a measuring apparatus of the powder method, and the numbers in the figure indicate the following. 1: powder sample, 2: fundamental wave cut filter 3: spectroscope, 4: photomultiplier, 5: amplifier (11): wavelength 1.064 μm, (12): 0.532 μm

Claims (3)

(57) [Claims] 1. A nonlinear optical material comprising a mesoionic compound or an acid adduct thereof. 2. The nonlinear optical material according to claim 1, wherein the mesoionic compound or an acid adduct thereof is a compound represented by the following general formula (I) or an acid adduct thereof. General formula (I) (Wherein, X represents a chalcogen atom or N-R ⁴ .R ^1,
R ² and R ³ represent a hydrogen atom, an alkyl group or an aryl group, and R ¹ and R ² may form a ring. R ⁴ represents an aryl group. ) 3. A method for converting an optical wavelength using the organic nonlinear optical material according to claim 1, wherein the conversion of the optical wavelength using the laser light and the nonlinear optical material is performed.