JP2547807B2 - Nonlinear optical material and orientation method thereof - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a non-linear optical material, and more particularly to a non-linear optical material suitable for a thin-film or fiber-shaped waveguide and an orientation method thereof.

[Prior art]

Conventionally, as a nonlinear optical material, an inorganic single crystal such as KDP or LiNbO ₃ or an organic single crystal such as urea has been known and used for a wavelength conversion element of a laser, for example. However, it is technically difficult to obtain a sufficiently large single crystal like this, and an inexpensive one cannot be obtained. In order to solve such problems, it has been attempted to obtain a large thin film or fiber single crystal by vapor deposition or zone melting in a capillary (Na
yay, BK; ACS sym, 153 (1983)). However, in such a method, it is necessary to control the single crystal in the phase-matched orientation necessary to efficiently obtain the second harmonic generation (SHG) and the third harmonic generation (THG), which are nonlinear optical effects. Is not easy.

Further, instead of using a single crystal, a method is known in which a guest compound having a large nonlinear optical constant is put in a host molecule and an electric field or a magnetic field is applied to orient the host compound in order to control the crystal structure.

For example, it has been attempted to align polar molecules by using the electric field orientation of the polymer liquid crystal with the polymer liquid crystal as the host and the polar molecule as the guest, and SHG has been observed by applying a voltage [Meredite C. et al. Morekiurus "(Meredity, GRet al; Macromoleclules, 15 , 13
Page 85, 1982].

In addition, as an example of aligning polar molecules in an amorphous polymer, an azo dye is dissolved in a polymethyl methacrylate resin to form a thin film, and then heated to a temperature equal to or higher than the glass transition point, and a voltage is applied to form the azo dye molecule. A non-linear optical constant of 6 × 10 ⁻⁹ esu was observed by cooling the array while fixing the structure. [Singer Kay
Dee, Thornie, Eee, Lalama Esjeay "Applied Fujitsukusu Letters (Singer, KD, S
ohn, JEand Lalama, SJ; Appl.Phys.Lett.,) 49 , 248
P. 1986].

JP-A-57-45519 and US Pat. No. 4,428,873 describe obtaining a polymer nonlinear optical substrate by adding a nonlinear optically responsive organic compound to a polymer-based substrate.

In addition, as described in JP-A-62-84139, there is a non-linear optical substrate using an acrylamide resin as a host polymer and a non-linear optically responsive organic compound as a guest.

Further, JP-A-62-246962 describes growing a compound having an asymmetric center in a polyoxyalkylene oxide matrix.

Such a polymer-based non-linear optical material is excellent in workability such as thinning in a state of retaining electron interaction that causes a non-linear optical effect, and is a material suitable for deviceization.

[Problems to be solved by the invention]

Generally, as the content of the guest molecule in the solid solution increases, the nonlinear optical effect increases in proportion to the amount,
It is difficult to uniformly blend a large amount of a low molecular polar compound as a guest in a high molecular polymer, for example, at least 20% by weight or more at a molecular level, and defects such as partial guest phase separation and crystallization are caused. May occur.

Further, in such a blended polymer, especially when the content of the low-molecular polar guest molecule is increased, the flexibility of the polymer itself is lost, and the mechanical strength tends to be significantly reduced.

Regarding the second-order nonlinear optical effect, even if the guest molecule alone has a large polarizability β, even if it is a centrosymmetric crystal, even if it is mixed with a conventional polymer, there is no SHG activity. . Therefore, it is usually necessary to form a film and apply an electric field or a magnetic field, or to stretch and orient the film.

In particular, in the conventional example, since the electric field energy is smaller than the thermal energy as shown in the report by Singer Kaday et al., Good molecular orientation and large nonlinear susceptibility are obtained even when the electric field is applied up to the dielectric breakdown. I couldn't get it.

Even when a polymer nonlinear optical substrate was obtained by adding a nonlinear optically responsive organic compound, it did not exceed the nonlinear susceptibility of the nonlinear optically responsive organic compound alone.

Further, as a method for obtaining a large nonlinear optical effect as a nonlinear optical element, it has been considered to increase the energy density of incident light. For this purpose, it is necessary to use a high-energy laser as the incident light or to focus the incident light, and the latter is especially important when the semiconductor laser is applied to a nonlinear optical element. Particularly suitable for the purpose is focusing of incident light by a thin film or fiber waveguide, and a large nonlinear optical effect has been reported (T. Taniuchi, JEE, High Tech Report, Novembar, 93 (1)
986)). However, in order to obtain such a waveguide, for example, in LiNbO ₃ , Ti and H are diffused and exchanged into a single crystal, which is time-consuming and difficult to control.

[Outline of Invention]

An object of the present invention is to provide a nonlinear optical material that can be applied to a waveguide having a sufficient nonlinear optical constant, instead of the conventional expensive single-crystal nonlinear optical material as described above. Further, an object of the present invention is to provide a non-linear optical material which can be easily formed into a thin film, has sufficient mechanical and expensive performance, and is suitable for device formation.

Therefore, in the present invention, a guest organic chemical compound having a large non-linear polarizability is easily and uniformly compatible in the host polymer compound, and the second-order and third-order nonlinear optical effects of the guest organic compound are To provide a novel nonlinear optical material that does not deteriorate in blending with the host polymer compound, has flexibility even when a large amount of guest organic compound is contained, and has excellent mechanical strength and processability. It is in.

Another object of the present invention is to blend a guest organic compound having a large β in the second-order nonlinear optical effect but having a centrally symmetric crystal in a guest organic compound alone and not showing any SHG activity with the host polymer compound. Accordingly, it is an object of the present invention to provide a nonlinear optical material capable of expressing a large SHG activity.

That is, the present invention is characterized by a nonlinear optical material containing a polyoxyalkylene matrix containing a palladisubstituted benzene derivative compound represented by the following general formula (2).

General formula (2) In the formula, A is an electron-donating substituent and B is an electron-withdrawing substituent.

[Detailed Description of Embodiments of the Invention]

The polyoxyalkylene used in the present invention is represented by the following formula (1).

During _R-O n (1) the formula, R represents an alkylene group having 1 to 6 carbon atoms, n represents
It is 10 to 200,000.

R may be an alkylene group having 1 to 6 carbon atoms, but if the number of carbon atoms is 7 or more, the compatibility between the electron-withdrawing substituent and the compound having the electron-donating substituent is reduced, which is excellent. You cannot get a physical film. Among them, R is particularly preferably polyoxyalkylene having 2 to 4 carbon atoms.

The polyoxyalkylene is effective even if it is a part of matrix, and can be used by introducing it into other compounds by copolymerization or by mixing with other compounds by blending.

The method of introduction by copolymerization is as follows.

It is used as a side chain of the main chain polymer.

In this case polyoxyalkylene shown at least in part by R-O _n the backbone represented by A _m is sufficient if attached. Moreover, it may have a crosslinked structure.

A repeating unit is configured and used as a main chain.

_{-AR-O n BR-O n} 'CR-O n' ... A,
B, C ... may have the same structure or different structures.

The structure described above is used as a ring structure.

More specifically, compounds having a polyoxyalkylene include the following.

_{R 1 COOR-O n COOR 2} (.n = 2~10000 represents an alkyl group of _{.R 1, R 2 = C 1} ~C 20 showing the alkylene group R = C ₁ ~C ₆₎ (Indicates R = C _{1 to} C ₆ alkylene group. R ₃ , R ₄ = H or C ₁
An alkyl group having -C _20. .n indicating the n 'and _{n = 2~10000) HOR 1 -O n} R 2 -O n' R 3 -O n 'H (R 1, R 2, an alkylene group of R ₃ = C ₁ ~C _6, n ′, n ″
= 2 to 100000) (R = C ₁ -C ₆ alkylene group. N = 10-200000,
m = 10 to 100,000, X represents H—, CH ₃ — or a halogen group. ) (R = C _{1 to} C ₆ alkylene group, n = 10 to 100000 R ₁ = C ₁
To C ₁₈ alkylene group, cyclohexylene group, phenylene group, biphenylene group or toluylene group. m = 10
~ 10000) (R = C _{1 to} C ₆ alkylene group, n = 10 to 100000 R ₁ = C ₁
To C ₁₈ alkylene group, cyclohexylene group, phenylene group, biphenylene group, terphenylene group or toluylene group. m = 10 to 10000) Examples of the electron-donating substituent bonded to the above-mentioned palladium-substituted benzene dielectric include an amino group, an alkyl group (methyl,
Ethyl, isopropyl, n-propyl, n-butyl, t
-Butyl, sec-butyl, n-octyl, t-octyl, n-hexyl, cyclohexyl, etc.), alkoxy group (methoxy, ethoxy, propoxy, butoxy, etc.), alkylamino (N-methylamino, N-ethylamino, N) -Propylamino, N-butylamino, etc.), hydroxyalkylamino group (N-hydroxymethylamino, N- (2-hydroxyethyl) amino, N- (2-hydroxypropyl) amino, N-
(3-hydroxypropyl) amino, N- (4-hydroxy) butylamino, etc.), dialkylamino group (N, N-dimethylamino, N, N-diethylamino, N, N-
Dipropylamino, N, N-dibutylamino, N-methyl-N-ethylamino, N-methyl-N-propylamino, etc., hydroxyalkyl-alkylamino group (N-hydroxymethyl-N-methylamino, N- Hydroxymethyl-N-ethylamino, N-hydroxymethyl-N-ethylamino, N- (2-hydroxyethyl) -N-methylamino, N- (2-hydroxyethyl) -N-methylamino, N- (3 -Hydroxypropyl) -N-methylamino, N- (2-hydroxypropyl-N-ethylamino, N- (4-hydroxybutyl) -N-butylamino, etc.), dihydroxyalkylamino group (N, N-di) Hydroxymethylamino, N, N-di- (2-hydroxyethyl) amino, N,
N, -di- (2-hydroxypropyl) amino, N, N-
Di (3-hydroxypropyl) amino, N-hydroxymethyl-N- (2-hydroxyethyl) amino, etc.), a mercapto group, a hydroxy group or a proton group can be used, and as the electron withdrawing substituent, A nitro group, a cyano group, a halogen atom (chlorine atom, bromine atom), a trifluoromethyl group, a carboxyl group, a carboxyester group, a carbonyl group or a sulfonyl group can be used.

Specific examples of the palladium-substituted benzene dielectric compound used in the present invention are shown below.

(1) 4-Aminoacetophenone (2) 4-Aminobenzoic acid (3) 4-Amino-α, α, α-trifluorotoluene (4) 4-Aminobenzonitrile (5) 4-Aminocinnamica Sids (6) 4-Aminophenol (7) 4-Bromotoluene (8) 4-Bromoaniline (9) 4-Bromoanisole (10) 4-Bromobenzaldehyde (11) 4-Bromobenzonitrile (12) 4-Chloro Toluene (13) 4-Chloroaniline (14) 4-Chloroanisole (15) 4-Chlorobenzaldehyde (16) 4-Chlorobenzonitrile (17) 4-Cyanobenzaldehyde (18) α-Cyano-4-hydroxycinnamic acid Sids (19) 4-Cyanophenol (20) 4-Cyanopyridine-N-oxide (21) 4-Fluorotoluene (22) 4-Fluoro Aniline (23) 4-Fluoroanisole (24) 4-Fluorobenzaldehyde (25) 4-Fluorobenzonitrile (26) 4-Nitroaniline (27) 4-Nitrobenzaldehyde (28) 4-Nitrobenzamide (29) 4-Nitro Benzoic acid (30) 4-nitrobenzonitrile (31) 4-nitrobenzyl alcohol (32) 4-nitrocinnamaldehyde (33) 4-nitrocinnamic acid (34) 4-nitrophenol (35) 4-nitrophenol Enetol (36) 4-Nitrophenylacetate (37) 4-Nitrophenylhydrazine (38) 4-Nitrophenylisocyanate (39) 4-Nitrotoluene (40) 4-Nitri-α, α, α-trifluoro Toluene The above-mentioned palladium-substituted benzene has an electron-donating substituent and an electron-withdrawing substituent at the para-position. Therefore, the dipole moment in the molecule becomes maximum.

The second-order micro nonlinear optical constant (β) is ω _(ng) : Energy difference between ground and excited states h: Planck's constant r _{i (gn)} : Dipole matrix element between ground and excited states e: Electronic charge △ r _{i (n)} = r _{i (nn)} −r _{i (gg)} (Ward.JF; Review of Modern Physics, 3rd
(Vol. 7, p. 1, 1965), it has a large dipole moment, but in general, compounds with a large dipole moment tend to have inversion symmetry centers in their crystal structure,
In most cases SHG is not observed.

On the other hand, when the non-linear optical element of the present invention uses polyoxyalkylene, it is possible to obtain the non-linear optical effect.

Therefore, in the present invention, the inversion symmetry center of the compound having such a large dipole moment is defined as polyoxyalkylene.
It can be removed by the presence of the matrix. This release of the center of inversion symmetry is considered to be because polyoxyalkylene forms a helical structure in its crystalline state, and the above-mentioned palladi-substituted benzene is uniaxially oriented between the helices.

Since the dielectric compound interacts and is uniaxially oriented in such a spiral structure of the polyoxyalkylene matrix, phase separation or misalignment may occur even when the above-mentioned derivative compound is contained in a large amount. Does not cause uniform crystallization. Similarly, since the helical structure of the polyoxyalkylene matrix is maintained, the nonlinear optical material of the present invention has good flexibility and mechanical strength, and is suitable for use as a thin film or a fiber.

In the non-linear optical material of the present invention, the polyoxyalkylene matrix and the dielectric compound have a special orientation due to interaction, and the orientation treatment such as an electric field, a magnetic field, and a stretching makes it possible to achieve the above-mentioned melody efficiency. According to the report of R. et al. And the report of Singer K. D. et al., A high orientation that cannot be obtained in principle can be obtained, and it is possible to exhibit an extremely excellent nonlinear optical effect.

As such an alignment treatment method, the above-described polyoxyalkylene matrix and the dielectric compound are heated to a temperature not higher than the melting point which does not cause an interaction, and an electric field is applied in the same direction as the photoelectric field of the incident light used for the nonlinear optical effect. It is desirable to cool to below the melting point while applying. At this time, the cooling rate is set to 100 degrees / sec or less so that the interaction between the polyoxyalkylene matrix and the dielectric compound is maximized so that the action with the electric field is maximized.
By setting the speed to below the degree / sec, an extremely excellent nonlinear optical effect can be obtained.

FIG. 3 is a representative model example of composition dependence under a constant electric field and electric field dependence at a constant composition when the polyoxyalkylene matrix and the above-mentioned dielectric compound are oriented by interaction with each other. And shown in FIG.

In the non-linear optical material of the present invention, the largest micro-nonlinear optical constant is obtained by aligning the dipole moments of the Palladi-substituted benzene having an electron-donating substituent and an electron-withdrawing substituent in the electric field direction by such a treatment method. Since β can be aligned perpendicular to the film surface, this nonlinear optical effect can be used most effectively as a thin film waveguide.

Similarly, an array of molecules can be obtained by applying a magnetic field above the melting point and cooling below the melting point. Further, stretching treatment is also effective for orientation.

The nonlinear optical element of the present invention can be obtained by adding a para-substituted benzene having an electron-donating substituent and an electron-withdrawing substituent to a solution of polyoxyalkylene, casting the uniform solution and then drying. At this time, by heating to 40 to 120 ° C., a good film in which the polyoxyalkylene and the compound having an electron donating substituent and an electron withdrawing substituent are not separated can be obtained. Further, when a DC electric field is applied to the film at a temperature higher than the melting point and the film is cooled to a temperature lower than the melting point while the film is applied, better performance can be obtained. As a method of applying a DC electric field, electrodes may be provided on both surfaces of the film, or corona discharge or the like may be used.

FIG. 1 is a sectional view of the nonlinear optical element 1 according to the present invention. In the figure, 11 is a substrate such as glass or plastic,
A lower electrode 12 is formed of a conductor such as ITO (indium-thein-oxide), tin oxide, indium oxide, gold, silver, copper, or aluminum. 13 is a low refractive index layer which can be formed of an organic thin film or an inorganic thin film, specifically, vinylidene fluoride-trifluoroethylene copolymer or Si.
O ₂ or the like is used. Reference numeral 14 denotes a waveguide formed of the nonlinear optical material of the present invention. Reference numeral 15 denotes an upper electrode made of aluminum.

When the laser wavelength lambda ₀ is oscillated from the laser light source 16 toward the nonlinear optical element 1 according to the present invention, so that the laser of the wavelength lambda _0/2 is output from the nonlinear optical element 1. 17 shows an optical modulator such as an optical switching element and an optical deflector, and 18 is a condenser lens.

Hereinafter, the content of the present invention will be described in more detail with reference to Examples.

[Example 1] 1.03 g (23 mm) of polyoxyethylene (POE) having a molecular weight of 20,000
ol) and para-nitroaniline (P-NA) 0.44 g (3 mmol)
Was added to 10 ml of benzene and dissolved by heating for 5 hours. When this solution was added to a dish and evaporated to dryness while maintaining at 60 to 80 ° C, a uniform film was obtained.

When this film was irradiated with an Nd-YAG laser (wavelength 1.064 μm), generation of optical second harmonics (wavelength 0.532 μm) was observed by the powder method with an intensity of about 5% of urea by the powder method.

[Example 2] Instead of the polyoxyethylene (POE) having a molecular weight of 20,000 used in Example 1, polyoxyethylene (P
OE) was used, and acetonitrile was used instead of benzene as a solvent, to prepare a composition by the same method as in Example 1. The phase diagram at this time is shown in FIG. The transition temperature was measured using Perkin Elmer DSC-7.

[Example 3] 2.12 g (48 mmol) of polyoxyethylene having a molecular weight of 5,000,000 and 1.57 g (11 mmol) of para-nitroaniline were added to 100 ml of acetonitrile and dissolved by heating for 5 hours. When this solution was added to a dish and evaporated to dryness while maintaining at 60 to 80 ° C,
A uniform film was obtained.

Aluminum foil was adhered to both sides of this film (thickness: 200 μm), the temperature was raised to 80 ° C. while slowly applying a DC electric field of 1000 V, and slowly cooled to room temperature. When the Nd-YAG laser (wavelength 1.064 μm) was irradiated after removing the electrode of this film, the photomultiplier generated the second harmonic light (wavelength 0.532 μm) with about 8 times the intensity of urea by the powder method. Was observed.

Example 4 1.0 g of polyethylene glycol stearate having an average molecular weight of about 1500 as shown below and PCOO (CH ₂ CH ₂ O) _n COOR R = stearate group Kaman's Emanone 3299 para-nitroaniline 0.2 g was added to 30 ml of methanol and dissolved by heating for 1 hour.

This solution is cast on a plate, and the thickness is about 200μ.
m uniform film was obtained.

An aluminum foil was adhered to both surfaces of the film, and while applying a DC electric field of 1000 V, the temperature was raised to 80 ° C., and the film was slowly cooled to room temperature. By removing the electrode of this film, Nd-YAG
When irradiated with a laser (wavelength 1.064 μm), the light second harmonic (wavelength 0.532
μm) was observed by a photomultiplier.

Example 5 1.0 g of a polyethylene glycol derivative having an average molecular weight of about 345 as shown below, Nippon Oil & Fats DA-35OF P-nitroaniline 0.2g was added to 20ml of ethanol, and 1
It was heated and dissolved for an hour.

This solution is cast on a shearle to a thickness of about 200 μm
Was obtained.

An aluminum foil was adhered to both surfaces of the film, and while applying a DC electric field of 1000 V, the temperature was raised to 80 ° C., and the film was slowly cooled to room temperature. By removing the electrode of this film, Nd-YAG
When irradiated with a laser (wavelength 1.064 μm), the second harmonic wave (wavelength 0.532
μm) was observed by a photomultiplier.

Example 6 Block Copolymer of Ethylene Oxide and Propylene Oxide 1.0 g HOC ₂ H ₄ O _n (C ₃ H ₆ -O) _m- (C ₂ H ₄ O) _n -H Molecular Weight M = 3250 Nicoyo PE-68 manufactured by Sanyo Kasei, 0.2 g of para-nitroaniline and 20 ml of benzene and 10 ml
It was heated and dissolved in a mixed solvent of methanol.

This solution is cast on a shearle to a thickness of about 200 μm
Was obtained.

An aluminum foil was adhered to both surfaces of the film, and the temperature was raised to 80 ° C. while applying a DC electric field of 1000 V, and the film was slowly cooled to room temperature. When the electrode of this film was removed and the film was irradiated with an Nd-YAG laser (wavelength 1.064 μm), the second harmonic wave (wavelength 0.532 μm) was emitted at about 8 times the intensity of urea by the powder method.
The occurrence of m) was observed by a photomultiplier.

[Example 7] 1.0 g of polyoxyethylene having a molecular weight of 5,000,000, 0.25 g of butyral resin (BL-1 manufactured by Sekisui Chemical Co., Ltd.), and 0.25 g of para-nitroaniline were dissolved by heating in a mixed solution of 20 ml of benzene and 10 ml of methanol. did.

This solution is cast on a shearle to a thickness of about 200 μm
Was obtained.

An aluminum foil was adhered to both surfaces of the film, and the temperature was raised to 80 ° C. while applying a DC electric field of 1000 V, and the film was slowly cooled to room temperature. When the electrode of this film was removed and the film was irradiated with an Nd-YAG laser (wavelength 1.064 μm), the second harmonic wave (wavelength 0.532 μm) was generated at about 15 times the intensity of urea by the powder method.
The occurrence of m) was observed by a photomultiplier.

[Example 8] 1.0 g of polyoxytetramethylene glycol having a molecular weight of 3000 [PTMG3000 (Sanyo Kasei Co., Ltd.)] and 0.2 g of para-nitroaniline were dissolved by heating in a mixed solvent consisting of 30 ml of benzene and 10 ml of methanol.

This solution is cast on a shearle to a thickness of about 200 μm
Was obtained.

An aluminum foil is adhered to both sides of this film, and while applying a DC electric field of 1000 V, the temperature is raised to 70 ° C. and slowly 5 ° C.
Cooled down. By removing the electrode of this film, Nd-YAG
When irradiated with a laser (wavelength 1.064 μm), the light second harmonic (wavelength 0.532
μm) was observed by a photomultiplier.

[Explanation of effects]

As described above, the non-linear optical composition of the present invention has a large non-linear optical effect (SH) expected from a micro-nonlinear optical constant originally possessed by a palladium-substituted benzene derivative and a paraoxyalkylene which originally do not have a non-linear optical effect.
G), it is possible to obtain a thin film with good mechanical and optical strengths, making it easy to apply nonlinear optical compositions to optical integrated circuits and optoelectronic integrated circuits. I made it.

[Brief description of drawings]

FIG. 1 is a sectional view of a nonlinear optical element according to the present invention. FIG. 2 is a phase diagram of the composition used in Example 2. FIG. 3 is a diagram for explaining the composition dependence of the nonlinear optical effect. FIG. 4 is a diagram for explaining the electric field dependence of the nonlinear optical effect.

Continuation of the front page (56) Reference JP-A-62-246962 (JP, A) Journal of Materials Sciences Letters Vol. 6 No. 2 February 1987 P.M. 167-170

Claims (4)

(57) [Claims] 1. A non-linear optical material characterized by containing a compound represented by the following general formula (2) in a polyoxyalkylene matrix. General formula (2) (In the formula, A represents an electron-donating substituent and B represents an electron-withdrawing substituent) 2. The electron-donating substituent is an amino group, an alkyl group, an alkoxy group, an alkylamino group, a hydroxyalkylamino group, a dialkylamino group, a hydroxyalkyl-alkylamino group, a dihydroxyalkylamino group, a mercapto group, The nonlinear optical material according to claim 1, which is a hydroxy group or a proton group. 3. The patent claim 1, wherein the electron-withdrawing substituent is a nitro group, a cyano group, a halogen atom, a trifluoromethyl group, a carboxyl group, a carboxyester group, a carbonyl group or a sulfonyl group. Non-linear optical material. 4. A non-linear optical material containing a compound represented by the following general formula (2) in a polyoxyalkylene matrix is represented by the general formula (2): (In the formula, A represents an electron-donating substituent and B represents an electron-withdrawing substituent.) A method for aligning a non-linear optical material, which is heated to a melting point or higher and cooled to the melting point or lower while applying a DC electric field.