JPH03154035A - Organic nonlinear optical material and element using the same - Google Patents

Abstract

PURPOSE:To obtain the org. nonlinear optical material which exhibits a high quadratic nonlinear optical effect and decreases light absorption in the optical wavelength region to be used and the element using this material by consisting the material of a compd. expressed by prescribed general formula. CONSTITUTION:This org. nonlinear optical material consists of the compd. expressed by the general formula I. In the formula, X denotes a hydrogen atom or electron-donative group. The material A made of this constitution is used in the optical waveguide part. For example, an optical wavelength converting element B has the structure in which the core 1 as the optical waveguide part formed of the material A is coated with a clad 2 consisting of a medium (isotropic medium) consisting of glass or the like which does not exhibit the quadratic nonlinear optical effect. Light of a laser beam, etc., is condensed by a lens, etc., and is made incident to the core 1 from one end face of the element B. The material B forming the core 1 exhibits the high quadratic nonlinear optical effect and, therefore, the light emitted from the other end face of the core 1 includes basic waves and second harmonic waves. The second harmonic waves are taken out by separating the same by a spectroscopic means, such as prism.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to an organic nonlinear optical material suitably used in the field of optoelectronics and a nonlinear optical element using the same.

<Prior art and problems to be solved> Nonlinear optical effect is a nonlinear optical effect in which polarization P induced by an electric field applied inside a crystal is expressed as °, P−X"E+X"E
-E+X(3)E -E -E+...X(n) =n
The following nonlinear susceptibility E: This is an optical effect that occurs due to nonlinearity caused by having a second-order or higher-order term in the electric field vector. Second-order nonlinear optical phenomena include second harmonic generation, optical rectification, optical mixing parametric amplification, and Pockels effect, and third-order phenomena include third harmonic generation, optical bistability, Kerr effect, etc. be.

In particular, the second-order nonlinear optical effect that occurs in proportion to the square of the electric field of light can be applied to nonlinear optical elements such as optical wavelength conversion elements and optical modulation elements that promise the development of the optoelectronics field. Therefore, it is attracting a lot of attention.

The materials that make up these devices are currently KH2P.
Only some inorganic materials such as O2 are in practical use. However, the nonlinear optical constants of these inorganic materials are small;
Therefore, the operation of the device requires extremely high voltage or extremely strong light intensity. For this reason, there is an extremely strong demand for materials with a large nonlinear optical effect, and various materials have been searched for. Among inorganic materials, lithium niobate (L i Nb03) has the largest nonlinear optical constant, but lithium niobate causes a partial change in refractive index when irradiated with strong laser light, and is easily exposed to light. However, it has the disadvantage of being damaged by damage, so it has not been put into practical use yet.

Recently, organic nonlinear optical materials have attracted attention because they are essentially superior to inorganic materials in terms of fi) large nonlinear polarizability, (i) high photodamage resistance, and (iii) fast to fast electric field response.In particular, 2 It is attracting attention as a material for a second harmonic generation element that converts the wavelength of incident light (fundamental wave) to 172 nm using second harmonic generation (SHG), which is one of the following nonlinear optical phenomena.

As the organic nonlinear optical material, for example, the following N
-Methyl-N-(4-nitro)phenylaminoani7tonitrile (hereinafter abbreviated as NPA N) 2-methyl-4-nitroaniline (hereinafter abbreviated as MNA), p
-nitro-(2-hydroxymethyl-pyrrolinyl)phenylene (hereinafter abbreviated as NPP) and the like.

NPAN MNAPP However, even if these organic crystalline materials have a relatively large hyperpolarizability β, their crystal structure has a center of symmetry, so they often do not produce second-order nonlinear optical phenomena in the crystalline state. was there.

That is, the molecular polarization μ is expressed by the following formula, μ mound α E + βE-E + γ E-E-E +...
...[α, β, 72641st, 2nd, and 3rd order molecular hyperpolarizabilities, E: Electric field vector The larger each hyperpolarizability, the larger the microscopic polarization and the greater the nonlinear optical phenomenon, but the above Polarization P indicates macroscopic polarization of the crystal, and when the crystal structure has a center of symmetry, no second-order nonlinear optical phenomenon occurs. Therefore, although the molecule itself has a large ability to handle nonlinear optical phenomena, there are cases in which second-order nonlinear phenomena do not occur due to the inversion symmetry of the crystal structure. In this way, the optical properties of organic crystal materials are greatly influenced not only by the properties of the molecules but also by the molecular arrangement in the crystal, but the molecular arrangement in organic molecular crystals is unique depending on the individual molecular species in a certain temperature range. It is very difficult to control the molecular arrangement in the crystal. Therefore, there is a problem that the optical properties of the molecules themselves are affected by the molecular arrangement, and the inherent optical properties of the molecules constituting the organic crystal material cannot be fully exhibited.

In addition, in the second harmonic generation element, in order to efficiently extract the obtained second harmonic, it is necessary that the organic nonlinear optical material used in the element has low light absorption in the optical wavelength range in which it is used. It is.

For example, as a nonlinear optical material for an optical wavelength conversion element used in short wavelength technology for semiconductor lasers of 780r+n+ to 840rv, 390 nm, which is the second harmonic region, is used.
A nonlinear optical material with low light absorption in the -420nIn wavelength region is preferable.

However, the above-mentioned NPAN is conventionally known.

Organic nonlinear optical materials such as MNA and NPP have a problem in that most of them exhibit large optical absorption in the wavelength range of 390 nm to 420 nm.

The present invention has been made in view of the above problems, and provides an organic nonlinear optical material that exhibits a large second-order nonlinear optical effect and has low light absorption in the optical wavelength region in which it is used, and an element using the same. With the goal.

In order to solve the above problem, the inventors used the molecular orbital method to predict the optical absorption maximum wavelength (λmax) and the second-order hyperpolarizability β, and thereby determined a molecular structure suitable for nonlinear optical elements. By using the method of
We have discovered a new fact that the compound represented by the following general formula (I) exhibits a high second-order nonlinear optical effect and can be particularly suitably used as an organic nonlinear optical material for second harmonic generation elements. This can be confirmed by the MO method. P P P-MO
The method is a type of molecular orbital method, and is a simple and widely used calculation method [A, Martln, Act
a Chemica Acadcmiae Scint.
iarum Hungaricae, 84.259 (
I975)].

Furthermore, using each molecular parameter obtained by the P P P -MO method, the secondary hyperpolarizability β can be calculated from the following formula [J, L, Oudar, J,
Chem.

Phys, 67, 448 (I977)].

That is, the organic nonlinear optical material according to the present invention is composed of the compound represented by the above general formula (I).
be a sign.

Further, the nonlinear optical element of the present invention has the above general formula (I)
It is characterized in that a compound represented by is used in the optical waveguide.

The fact that the second hyperpolarizability β of the compound represented by the general formula (I) is large means that P P P (Pariser-Parr-
Pole) −2m [w2 −(2f+ω)
2][v 2 -(4(IJ) 2][e: Charge of electron, 4: h/2π (h is blank constant), m: Mass of electron, -・Energy difference between two ground state and excited state,
hω: Incident light energy r: Oscillator strength, Δμ
=Difference in dipole e moment between ground state and excited state] By the above P P P-MO method, in the above general formula (I),
is fluorine, the maximum optical absorption wavelength (λ
max) was calculated to be 359 nm.

Further, when the second-order hyperpolarizability β of the above compound was calculated using the above formula, it was found to be 24 x 10-'' esu.

It should be noted that Shimizu et al. reported that the value of the secondary hyperpolarizability β calculated using the P P P -h10 method and the above formula is in good agreement with the above-mentioned measured value (Chemical Society of Japan). Proceedings of the Autumn Annual Meeting, 1987), it is appropriate to use the P P P-MO method and the above formula to calculate the second-order hyperpolarizability β.

As described above, the compound represented by the general formula (I) according to the present invention is the compound represented by the above-mentioned MNA (I7X10"esu)
etc., the second-order hyperpolarizability β is large, but the optical absorption wavelength region is 4
Because it is on the order of 00 nm, it has a secondary hyperpolarizability β that is about 1.5 times that of compounds that are not used as nonlinear optical materials, and its light absorption wavelength region is shorter, so it is suitable as a nonlinear optical material. It can be used suitably.

Therefore, the organic nonlinear optical material composed of the compound represented by the general formula (I1) has a large second-order hyperpolarizability β, has a remarkable nonlinear optical effect, and is a material for nonlinear optical elements used in the optoelectronics field. For example, it is suitable as a material for optical wavelength conversion elements, a material for optical modulation elements such as a phase modulation element, an amplitude modulation element, a frequency modulation element, a pulse modulation element, and a polarization plane modulation element.

The present invention will be explained in detail below.

In addition to a hydrogen atom, the above X may include an electron-donating group such as methyl, ethyl, propyl, isopropyl, butyl,
Alkyl groups such as tert-butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl;
Hydroxyl group; methylol, 2-hydroxyethyl,
Hydroxyalkyl groups such as 3-hydroxypropyl; methoxy, ethoxy, propoxy, isopropoxy, butoxy, isobutoxy, tert-butoxy, pentyloxy, hexyloxy, heptyloxy, octyloxy, nonyloxy, decyloxy, undecyloxy,
Alkoxyl groups such as dodecyloxy, tridecyloxy, tetradecyloxy, and pentadecyloxy; Mercapto groups: Alkylthio groups such as methylthio, ethylthio, propylthio, butylthio, and hexylthio; May have substituents such as hensylthio and phenylthio. Aralkylthio or arylthio group; amino, methylamino,
ethylamino, propylamino, isopropylamino,
Butylamino, hexylamino, dimethylamino, methylethylamino, diethylamino, dipropylamino,
Amino groups that may have an alkyl group such as dibutylamino: Arylamino groups such as benzylamino, benzhydryl, and tritylamino: Halogen atoms such as fluorine, chlorine, and iodine; Substituted with halogen atoms such as fluorine, chlorine, and iodine phenyl group, the above alkyl group, hydroxyl group, hydroxyalkyl group, alkoxy group, mercapto group, alkylthio group, aralkylthio group or arylthio group which may have a substituent, alkyl Examples include an amino group, an aralkylamino group, an arylamino group, which may have a group.

Among the above electron-donating groups, a fluorine atom is particularly preferred.

In addition, the above substituents may be substituted at appropriate positions, or
In order to increase the second-order molecular hyperpolarizability, it is preferably located at the 3rd or 4th position with respect to the carbon atom of the benzene ring that is bonded to the nitrogen atom of the pyrazoline ring, and in particular, the 4th position is preferred. preferable.

The organic nonlinear optical material described above can be used for an optical waveguide part of a nonlinear optical element.

Molecular Electronics 1.2
5 (I91!5) etc.

In this case, since the light is confined within the waveguide, the optical power density increases, and the interaction length can be increased, making it possible to achieve high efficiency, and furthermore, it is possible to achieve phase matching using mode dispersion. be.

Below, the nonlinear optical element of the present invention using the above organic nonlinear optical material will be explained in detail based on the accompanying drawings.

FIG. 1 is an example of the optical wavelength conversion element of the present invention, and shows a schematic diagram of an optical fiber type optical wavelength conversion element as a second harmonic generation element. The core is an optical waveguide made of nonlinear optical material (
I) is a cladding (2
), and in the same figure, the dash-dot line indicates the fundamental wave of the incident light, and the dash-dot line indicates the second harmonic. Light such as a laser beam is focused by a lens or the like, and is incident on the core (I) from one end surface of the optical wavelength conversion element. Since the nonlinear optical material forming the core (I) exhibits a large second-order nonlinear optical effect, the light emitted from the other end surface of the core (I) contains the fundamental wave and the second harmonic, and is The second harmonic is extracted by separating it using a spectroscopic means.

Further, FIGS. 2 and 3 are schematic diagrams showing other examples of the optical wavelength conversion element, respectively, and in the drawings, the dashed-dot line and the dashed-two dotted line have the same meanings as in FIG. 1, respectively.

In the optical wavelength conversion element shown in FIG. 2, an optical waveguide section (21) made of the above-mentioned nonlinear optical material is formed on a substrate (22) made of an isotropic medium, and the optical wavelength conversion element shown in FIG. In a wavelength conversion element, a substrate (
32) and a top layer (33) also made of an isotropic medium.
an optical waveguide section (31) made of the above-mentioned nonlinear optical material between
or is formed. The above optical wavelength conversion element is used in the same manner as the optical wavelength conversion element shown in FIG.

Further, it is possible to use a conventionally used device as a light modulation element. As an example, FIG. 4 shows a schematic diagram of a horizontally operated optical waveguide type optical modulation element as a phase modulation element, and shows a substrate (42
) is provided with an optical waveguide (41) made of a nonlinear optical material, and two electrodes (43) are provided at opposing positions along the length direction via the optical waveguide (41). An electric field is formed by applying a voltage between the electrodes (43). In the above device, the optical waveguide (
41) Light incident from one end in the length direction passes through the optical waveguide (
When the light passes through the optical waveguide (41) and is emitted from the other end surface, the optical waveguide (41) is emitted from the other end surface.
When the refractive index of the nonlinear optical material constituting I) changes, the phase of the emitted light also changes. Since the refractive index of the nonlinear optical material changes depending on the applied voltage, the phase of the emitted light can be modulated by changing the applied voltage between the electrodes (43).

In the optical wavelength conversion element shown in FIGS. 1 to 4 above, the core (I) and the optical waveguide (21) (31) (41
) is formed by, for example, heating and melting a nonlinear optical material in a capillary made of an isotropic medium, on a waveguide substrate made of an isotropic medium, or between waveguide substrates made of an isotropic medium. This can be done by slow cooling to precipitate crystals, or by depositing crystals on a substrate by vacuum evaporation, high frequency sputtering, etc. Alternatively, from a solution in which a nonlinear optical material is dissolved in an appropriate organic solvent, A method may also be used in which crystals are deposited in the capillary, on the substrate, or between the substrates. Furthermore, in some cases, after treating the part of the capillary, on the substrate, or between the substrates that will be the contact interface with the nonlinear optical material with an alignment treatment agent, crystals of the nonlinear optical material are precipitated and grown to form optical wavelength conversion elements, etc. may be formed. Examples of alignment agents include inorganic salts and organic salts (e.g., hexadecyltrimethylammonium bromide), thin films made of suitable polymers (e.g., polyamide), metal complexes, metal thin films (e.g., obliquely deposited gold thin films), etc. etc.) etc. are exemplified.

It should be noted that the nonlinear optical element of the present invention is not limited to the above example, and can be used as an optical modulation element such as a vertical waveguide type optical modulator capable of amplitude modulation. In this case, it is also possible to apply a voltage directly to the crystal of the nonlinear optical material itself. Note that when using the above nonlinear optical element as a light modulation element, the electric field application direction for efficient phase modulation differs depending on the crystal symmetry of the nonlinear optical material, the direction of the crystal axis, etc. It is recommended to change the configuration of the .

<Examples> The present invention will be described in more detail below based on Examples.

Example 1 51.0 g (0.47 mol) of phenylhydrazine and 98 g (0.47 mol) of benzylacetophenone were dissolved in 150 C of acetic acid for one month. Then, add the solution to 90~
After stirring for 3 hours while maintaining the temperature at 100°C, the mixture was allowed to cool and -
I left it there day and night. The precipitated solid was separated by filtration and distilled water
Crude crystals were obtained by washing with yl and air drying. The crude crystals were dissolved in 400 xl of ethyl acetate, and 5 g of activated carbon was added thereto.
The mixture was heated at 0° C. for 2 hours, filtered hot to remove activated carbon, and then recrystallized from ethyl acetate to obtain white crystals.

According to the melting point, mass spectrometry and NMR, the crystal has a melting point of 1.3
．． 5-) It was confirmed that it was diphenylpyrazoline.

Melting point = 139-140°C Example 2 19.5 g of 4-fluorophenylhydrazine hydrochloride (
0.12 mol), benzalacetophenone 25.0 g
(0.12 mol) and 9.85 g of sodium acetate (
0.12 mol) to 400 xi of acetic acid, 90-10
The mixture was stirred for 12 hours while being maintained at 0°C, and then allowed to cool. The precipitated solid was separated by filtration, washed with 400 xl of ethyl acetate, and filtered. The obtained solid was dissolved in ethyl acetate again,
After adding 5 g of activated carbon and heating at 60° C. for 2 hours and removing the activated carbon by hot filtration, ethyl acetate was distilled off to obtain crystals. The obtained crystals were recrystallized each time using ethyl acetate and acetonitrile to obtain white crystals.

The melting point, mass spectrometry and NMR revealed that the above crystal had a 1-(
It was confirmed that it was 4-fluorophenyl)3,5-diphenylpyrazoline.

Melting point: 131-132°C Example 3 In place of 4-fluorophenylhydrazine hydrochloride, 3-
White crystals were obtained in the same manner as in Example 2, except that fluorophenylhydrazine hydrochloride was used.

The melting point, mass spectrometry and NMR revealed that the above crystal had a 1-(
It was confirmed that the product was 3-fluorophenyl)3,5-diphenylpyrazoline.

Melting point = 135-136°C Example 4 Mi-4- in place of 4-fluorophenylhydrazine hydrochloride
Yellow-white crystals were obtained in the same manner as in Example 2, except that methoxyphenylhydrazine hydrochloride was used.

The melting point, mass spectrometry and NMR revealed that the above crystal had a 1-(
It was confirmed that it was 4=-methoxyphenyl)3,5-diphenylpyrazoline.

Melting point: 142 to 143°C Each of the crystals obtained in Test Examples 1 to 4 had a wavelength of 1.0
When irradiated with Nd:YAG laser of 64//ffi, all crystals had a wavelength of 0.64//ffi, which is the second harmonic.
Generation of 532 μl of green light was observed.

The results show that the compounds obtained in Examples 1 to 4 exhibit a second-order nonlinear optical effect.

<Effects of the Invention> As described above, according to the nonlinear optical material of the present invention, the compound represented by the general formula (I) has a large secondary hyperpolarizability β and a light absorption wavelength range of short wavelengths. , since its crystal does not have an inversion symmetry center, the nonlinear optical material of the present invention containing at least this compound exhibits a significant nonlinear optical effect, and since its crystal does not have an inversion symmetry center, it has a particularly 2
It is suitable as the next nonlinear optical material.

Further, according to the nonlinear optical element of the present invention, since the above-mentioned nonlinear optical material is used in the leading technique, it exhibits a second-order nonlinear optical effect, and even a laser beam with a low optical intensity can generate a high-intensity second harmonic. It has the unique effect of being able to be separated and exhibiting an electro-optic effect even with a small voltage change.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of an optical wavelength conversion element as an embodiment of the nonlinear optical element of the present invention, and FIGS. 2 and 3 each show other examples of the nonlinear optical element as an optical wavelength conversion element. The schematic diagram, FIG. 4, is a schematic diagram showing an example of a nonlinear optical element as a phase modulation element. (I)... Core, (2J... Clad, (21) (31) (41)... Leading technique section, (22)
(32) (42)...Substrate, (33)...Top layer, (43)...Electrode.

Claims (1)

[Claims] 1. An organic nonlinear optical material comprising a compound represented by the following general formula (I). ▲There are mathematical formulas, chemical formulas, tables, etc.▼ (I) [In the formula, X represents a hydrogen atom or an electron-donating group] 2. Characterized by using the organic nonlinear optical material according to claim 1 in an optical waveguide. Nonlinear optical element.