JPH01523A - Nonlinear optical material and its orientation method - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of the Invention] The present invention relates to nonlinear optical materials, and particularly to nonlinear optical materials suitable for thin film or fiber waveguides and methods for orienting the same.

[Prior art]

Conventionally, inorganic single crystals such as KDP and LiNbO3, and organic single crystals such as urea have been known as nonlinear optical materials, and have been used, for example, in wavelength conversion elements of lasers.

However, it is technically difficult to obtain a sufficiently large single crystal, and it is not possible to obtain one at a low cost. To solve these problems, attempts have been made to obtain large single crystals in the form of thin films or fibers by vapor deposition methods or zone melting in capillaries (Nayay, B.; AC3sym, 15).
3 (1983)).

However, in this method, second harmonic generation (SHG) and third harmonic generation (THG), which are nonlinear optical effects, are
) It is not easy to control a single crystal in the phase-matched orientation necessary to efficiently obtain it.

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

For example, attempts have been made to align polar molecules using the electric field orientation of the polymer liquid crystal using a polymer liquid crystal as a host and polar molecules as a guest, and SHG has been observed by applying a voltage [Mereditage G-R et al. "Macromolecule J"

G, R, et al; Macromolecule
les, 15.1385 pages, 1982 Co.

In addition, as an example of orienting polar molecules in an amorphous polymer, an azo dye is dissolved in polymethyl methacrylate resin to form a thin film, and then heated above the glass transition point.
By applying a voltage to align the azo dye molecules and cooling to fix the structure, 6 x 10-'e
A nonlinear optical constant of su has been observed. [singer
K. D., Sohnjii E., Lalama Nis. G.I. Applied Physics Letters (S i
ng er, K, D.

5ohn, J.E., and Lalama, S.
J; Appl, Phys.

Lett, ) 49.248 pages, 1986].

JP-A-57-45519 discloses that a polymeric nonlinear optical substrate can be obtained by adding a nonlinear optically responsive organic compound to a polymeric compound as a substrate. USP44288
73.

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

Furthermore, JP-A-62-246962 describes the growth of compounds having asymmetric centers in polyoxyalkylene oxide matrices.

Such polymer-based nonlinear optical materials have excellent processability such as thin film formation while maintaining electronic interactions that produce nonlinear optical effects, and are suitable for device production.

[Problem that the invention seeks to solve]

Generally, as the content of guest molecules in the solid solution increases,
The nonlinear optical effect becomes thicker in proportion to the amount of the compound.
For example, it is difficult to homogeneously blend at a molecular level of less than 20% by weight, and defects such as partial phase separation of guest molecules and crystallization may occur.

In addition, in such a blend polymer, particularly when the content of low-molecular polar guest molecules increases, the flexibility of the polymer itself tends to be lost, and the mechanical strength tends to decrease significantly.

Regarding the second-order nonlinear optical effect, the polarizability β of a single guest molecule is large (in addition, if it is a centrosymmetric crystal, there is no SHG activity even when mixed with conventional polymers, or even if it shows only a small amount) Therefore, it is usually necessary to make it into a film and apply an electric or magnetic field, or to orient it by stretching.

In particular, in the conventional example, as shown in the report by Singer K. D. et al., the energy of the electric field is small compared to the thermal energy, so even if the electric field is applied to the point of dielectric breakdown, good molecular orientation and large nonlinear susceptibility can be achieved. I couldn't get it.

Further, even if a polymeric nonlinear optical substrate was obtained by adding a nonlinear optically responsive organic compound, the nonlinear susceptibility did not exceed the nonlinear susceptibility of the nonlinear optically responsive organic compound alone.

Furthermore, increasing the energy density of incident light has been considered as a method of obtaining a large nonlinear optical effect as a nonlinear optical element. For this purpose, it is necessary to use a high-energy laser for the incident light or to focus the incident light, and the latter is especially important when applying a semiconductor laser to a nonlinear optical element. Focusing of incident light using thin-film or fiber-like waveguides is particularly suitable for this purpose, and large nonlinear optical effects have been reported (T, Tanluchi, JEE, High Tec
hReport.

November, 93 (1986)). However, in order to obtain such a waveguide, for example, LiNbO
In No. 3, Ti and Hl were diffused and exchanged into a single crystal, which took time and was difficult to control.

[Summary of the 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 in place of the conventional expensive single-crystal nonlinear optical material as described above. Furthermore, the object of the present invention is to facilitate thinning of the film.
The object of the present invention is to provide a nonlinear optical material that has sufficient mechanical and optical strength and is suitable for device production.

Therefore, the present invention provides that a guest organic compound having a large nonlinear polarizability is easily and uniformly dissolved in a host polymer compound, and that the second-order and third-order nonlinear optical effects of the guest organic compound are To provide a new nonlinear optical material that does not deteriorate when blended with a host polymer compound, has flexibility even when containing a large amount of a guest organic compound, and has excellent mechanical strength and processability. be.

Another object of the present invention is to blend a guest organic compound with a host polymer compound, which has a large β in the second-order nonlinear optical effect, but is a centrosymmetric crystal when the guest organic compound alone exhibits no SHG activity. The object of the present invention is to provide a nonlinear optical material that can exhibit large SHG activity.

That is, the present invention is characterized by a nonlinear optical material containing a para-disubstituted benzene dielectric compound represented by the following general formula (2) in a polyoxyalkylene matrix.

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

[Detailed description of aspects of the invention]

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

MoR-0shi. (1) In the formula,
R represents an alkylene group having 1 to 6 carbon atoms, and n is 10 to 2
00,000.

As R, an alkylene group having 1 to 6 carbon atoms can be used, but if the number of carbon atoms is 7 or more, the compatibility with a compound having an electron-withdrawing substituent and an electron-donating substituent decreases, so that an excellent It is not possible to obtain a film with physical properties. Among these, R is particularly preferably polyoxyalkylene having 2 to 4 carbon atoms.

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

Examples of the introduction method by copolymerization include the following.

■Used as a side chain of the main chain polymer.

-(-Aji.

In this case, it is sufficient that the main chain represented by (A) is at least partially bound to the polyoxyalkylene represented by (-R-0). It may also have a crosslinked structure.

■Used as a main chain (configuring a repeating unit).

-A-11-R-0). B(-R-0ki-C-(-R-
0), . . . A, B, C . . . may have the same structure or different structures.

(2) The structures (2) and (2) above constitute a cyclic structure and are used.

More specifically, compounds having polyoxyalkylene include the following.

R,Coo(-R-0″+flC00R2(n=C,=
Indicates a C6 alkylene group. R,, R2=C1~C20
represents an alkyl group. n=2~10000)CH
3 (indicates an alkylene group where n=C, =C6. R3, R4=
Indicates an alkyl group of H or CINC. n′ and n
= 2-10000) HO-11-R, -03-7(-R2-0). , (−
R3-0),, H(R+, R2+ R3=C+~
Indicates a C6 alkylene group.

n, n', n' = 2~100000) 1,000 CH2-C
N□ ■ O ■ O÷R-0 arrow,,H (indicates an alkylene group where n=C, -C6.n=10
~200000, m=10~100000, X is H-,
Indicates CH3- or a halogen group. ) (n=C8-C6 alkylene group, n=10-10
0000R, =C, =C18 alkylene group, cyclohexylene group, phenylene group, biphenylene group or toluylene group. m = 10-10000)○ ○ (n=C, =C6 alkylene group, n=10-1000
00R, =C, ~C11+ alkylene group, cyclohexylene group, phenylene group, biphenylene group, terphenylene group, or tolylene group. m=10~10000
) Examples of the electron-donating substituents bonded to the Balady-substituted benzene dielectric mentioned above include amino groups, alkyl groups (methyl,
ethyl, isopropyl, n-propyl, n-butyl, t
-butyl, 5ec-butyl, n-octyl, t-octyl, n-hexyl, cyclohexyl, etc.), alkoxy groups (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-hydroxypropyl2amino, N-(4-hydroxy)
butylamino), dialkylamino group (N.

N-dimethylamino, N,N-diethylamino, NlN
-dipropylamino, N,N-dibutylamino, N-methyl-N-ditylamino, N-methyl-N-propylamino, etc.), hydroxyalkyl-alkylamino groups (N-hydroxymethyl-N-methylamino, −
Hydroxymethyl-N-ditylamino, 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 groups (N, N-di Hydroxymethylamino, N,N-di(2-hydroxyethyl)amino, N,N-di(2-hydroxypropyl)amino, N,N-di(3-hydroxypropyl/lz)amino, N-hydroxymethyl- N-(2-hydroxyethyl)amino, etc.), mercapto group, hasyano group, halogen atom (chlorine atom, bromine atom), trifluoromethyl group, carboxyl group, carboxyester group, carbonyl group, or sulfonyl group can be used. .

Specific examples of palladi-substituted benzene dielectric compounds 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-aminocinnamic acid (6 ) 4-Aminophenol (7) 4-bromotoluene (8) 4-bromoaniline (9) 4-bromoanisole (10) 4-bromobenzaldehyde (11) 4-
Bromobenzonitrile (12) 4-chlorotoluene (13) 4-chloroaniline (14) 4-chloroanisole (15) 4-chlorobenzaldehyde (16) 4-
Chlorobenzonitrile (17) 4-cyanobenzaldehyde (18) α-cyano-4-hydroxycinnamic acid (19)
4-cyanophenol (20) 4-cyanopyridine-N-oxide (21
) 4-fluorotoluene (22) 4-fluoroaniline (23) 4-fluoroanisole (24) 4-fluorobenzaldehyde (215)
4-fluorobenzonitrile (26) 4-nitroaniline (27) 4-nitrobenzaldehyde (28) 4-
Nitrobenzamide (29) 4-Nitrobenzoic acid (30) 4-Nitrobenzonitrile (31) 4-Nitrobenzyl alcohol (32) 4
-Nitrocinnamaldehyde (33) 4-Nitrocinnamic acid (34) 4-nitrophenol (35) 4-nitrophenethol (36) 4-nitrophenyl acetate (37) 4
-Nitrophenylhydrazine (38) 4-nitrophenyl isocyanate (39) 4-nitrotoluene (40) 4-nitri-α,α,α-trifluorotoluene The barade-substituted benzenes represented above are electron-donating substituted Since the group and the electron-withdrawing substituent are in the perla position, the dipole moment within the molecule is maximum.

The second-order micro nonlinear optical constant (β) is ω(ng):
Energy difference between the ground and excited states h Niblank constant r I (gn) 'Base and excited state quantity dipole matrix element e: Electronic charge △r 1(n) '' r !(nn) r i(g
g) is expressed as (Ward, J, F, ; Revie
of Modern Physics, Vol. 37, p. 1, 1965), but in general, compounds with a large dipole moment tend to have a center of inversion symmetry in their crystal structure. SHG is not observed in any case.

On the other hand, when polyoxyalkylene is used in the nonlinear optical element of the present invention, it is possible to obtain a nonlinear optical effect.

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

Since the dielectric compound interacts with the helical structure of the polyoxyalkylene matrix and is uniaxially oriented, phase separation and non-conformity occur even when a large amount of the aforementioned dielectric compound is contained. 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 in the form of a thin film or fiber.

In addition, in the nonlinear optical material of the present invention, the polyoxyalkylene matrix and the dielectric compound have a special orientation due to interaction, and the above-mentioned meridian G.R. It is possible to obtain a high degree of orientation that cannot be obtained in principle in the reports of Singer, K., et al., and Singer, K.D., and it becomes possible to express extremely excellent nonlinear optical effects.

As such an alignment treatment method, the aforementioned polyoxyalkylene matrix and dielectric compound are heated above their melting point, which is a temperature at which no interaction occurs, and an electric field is applied in the same direction as the optical electric field of the incident light used for the nonlinear optical effect. It is desirable to cool down to below the melting point. At this time, the cooling rate is set to 100 degrees/sec or less, more preferably 10 degrees/sec, so that the rate of interaction between the polyoxyalkylene matrix and the dielectric compound is maximized by the interaction with the electric field. By keeping e c or less,
Extremely excellent nonlinear optical effects can be obtained.

Figure 3 shows typical model examples of the composition dependence under a constant electric field and the electric field dependence at a constant composition when the polyoxyalkylene matrix and the dielectric compound described above interact and are oriented. It is shown in Figure 4.

In the nonlinear optical material of the present invention, the dipole moment of para-disubstituted benzene having an electron-donating substituent and an electron-withdrawing substituent is aligned in the electric field direction by such a treatment method, thereby achieving the largest micro-nonlinearity. It becomes possible to align the optical constant β4 perpendicularly to the film surface, and the nonlinear optical effect can be utilized most effectively as a thin film waveguide.

Similarly, molecular alignment can be obtained by applying a magnetic field above the melting point and cooling to 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 para-disubstituted benzene having an electron-donating substituent and an electron-withdrawing substituent to a polyoxyalkylene solution, casting the homogeneous solution, and then drying it. At this time, by heating to 40 to 120°C, a good film is obtained in which the compound having an electron-donating substituent and an electron-withdrawing substituent and the polyoxyalkylene do not separate. Further, better performance can be obtained by applying a direct current electric field to this film at a temperature above the melting point and cooling it to below the melting point while the field is being applied.

As a method of applying a DC electric field, electrodes may be provided on both sides of the film, or corona discharge or the like may be used.

FIG. 1 is a sectional view of a nonlinear optical element 1 according to the present invention. In the figure, 11 is a substrate made of glass, plastic, etc.
A lower electrode 12 is made of a conductor such as ITO (indium tin oxide), tin oxide, indium oxide, gold, silver, copper, or aluminum. Reference numeral 13 is a low refractive index layer which can be formed of an organic thin film or an inorganic thin film, and specifically, vinylidene fluoride-trifluoroethylene copolymer, SiO3, etc. are used. 14 is a waveguide formed of the nonlinear optical material of the present invention. Reference numeral 15 denotes an upper electrode made of aluminum.

The wavelength λ towards the nonlinear optical element l according to the invention.

When a laser is emitted from the laser light source 16, the wavelength λ is emitted from the nonlinear optical element l. /2 laser will be output. In addition, FIG. 17 shows an optical modulation device such as an optical switching element or an optical knitting device, and 18 is a condenser lens.

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

[Example 1] Polyoxyethylene (POE) with a molecular weight of 20,000 1.03
g (23 mmol) and para-nitroaniline (P-NA
) 0.44 g (3 m m o 1) of benzene 10
ml and heated to dissolve for 5 hours. When this solution was added to a Petri dish and evaporated to dryness while keeping it at 60-80°C,
A uniform film was produced.

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

[Example 2] Polyoxyethylene (P) with a molecular weight of 20,000 used in Example 1
Polyoxyethylene (OE) with a molecular weight of 600,000 was used instead of
A composition was prepared in the same manner as in Example 1, except that acetonitrile was used in place of benzene as a solvent. The phase diagram at this time is shown in FIG. Transition temperatures were measured using a PerkinElmer DSC-7.

[Example 3] 2.12 g of polyoxyethylene with a molecular ff of 15 million (
48 mmo+) and 1.57 g of para-nitroaniline (
The mixture was added to 100 ml of acetonitrile and dissolved by heating for 5 hours. Add this solution to a petri dish and add 60 to 8
A uniform film was obtained by evaporating to dryness while maintaining the temperature at 0°C.

Aluminum foil was adhered to both sides of this film (thickness: 200 μm), and while applying a DC electric field of too much, the temperature was raised to 80° C. and slowly cooled to room temperature.

The electrodes of this film were removed and the Nd-YAG laser (
When irradiated with light (wavelength: 1.064 μm), the second harmonic of light (wavelength: 0.532 μm) was approximately 8 times stronger than that of urea produced by the powder method.
The occurrence of m) was observed using a photomultiplier.

[Example 4] Polyethylene glycol distearate having an average molecular weight of about 1500 as shown below 1. Og and PCoo (C)
(2CI(20)ncOORR=Nistearate Kao■
0.2 g of para-nitroaniline (manufactured by Emanone 3299) was added to 30mj7 methanol and dissolved by heating for 1 hour.

Cast this solution on a Petri dish to a thickness of approximately 200 μm.
A uniform film of m was obtained.

Aluminum foil was attached to both sides of this film, and the temperature was raised to 80°C while applying a 1000V DC electric field, and slowly cooled to room temperature.The electrodes of this film were removed and the Nd
When irradiated with -YAG laser (wavelength: 1.064 μm), the generation of optical second harmonics (wavelength: 0.532 pm) was observed using photomallic pliers with an intensity approximately 6 times that of urea produced using the powder method. Ta.

[Example 5] 1.0 g of a polyethylene glycol derivative having an average molecular weight of about 345 as shown below and 0.2 g of H3 NOF type DA-350F P-nitroaniline were added to 20 ml of ethanol and dissolved by heating for 1 hour.

Cast this solution on a Petri dish to a thickness of approximately 200 μm.
A uniform film was obtained.

Aluminum foil was tightly attached to both sides of this film, and while applying a 1000V DC electric field, the temperature was raised to 80°C and slowly cooled to room temperature.The electrodes of this film were removed and the Nd
When irradiated with -YAG laser (wavelength: 1.064 .mu.m), the generation of optical second harmonics (wavelength: 0.532 .mu.m) was observed using a photomultiplier with an intensity about 8 times that of urea produced by the powder method.

[Example 6] 1.0 g of a block copolymer of ethylene oxide and propylene oxide as shown below.
H40)-H Molecular weight M=3250 Nikopol PE-68 manufactured by Sanyo Chemical Co., Ltd. and 0.2 g of para-nitroaniline at 20 mI! was heated and dissolved in a mixed solvent of benzene and methanol at 10 mA.

Cast this solution on a Petri dish to a thickness of approximately 200 μm.
A uniform film was obtained.

Aluminum foil was closely attached to both sides of this film, and the temperature was raised to 80° C. while applying a DC electric field of 1000 V, and then slowly cooled to room temperature. The electrodes of this film were removed and Nd-
When irradiated with a YAG laser (wavelength: 1.064 μm), the second harmonic of light (
The generation of wavelength 0.532 μm is a photomultiplier.
observed by.

[Example 7] Polyoxyethylene with a molecule fi of 5 million 1. og and
0.25 g of butyral resin (BL-1 manufactured by Block Chemical Co., Ltd.),
Rose-nitroaniline 0.25g with 20ml benzene and lomI! was heated and dissolved in a mixed solvent of methanol.

Cast this solution on a Petri dish to a thickness of approximately 200 μm.
A uniform film was obtained.

Aluminum foil was closely attached to both sides of this film, and the temperature was raised to 80° C. while applying a DC electric field of 1000 V, and then slowly cooled to room temperature. The electrodes of this film were removed and Nd-
When irradiated with a YAG laser (wavelength: 1.064 .mu.m), the generation of optical second harmonics (wavelength: 0.532 .mu.m) with an intensity approximately 15 times that of urea produced by the powder method was observed using a photomultiplier.

[Example 8] Polyoxytetramethylene glycol with molecule ff 13000 [manufactured by Sanyo Chemical Co., Ltd. PTMG3000'l 1. O
g and 0.2 g of para-nitroaniline were heated and dissolved in a mixed solvent consisting of 30 mj' of benzene and 10 m1 of methanol.

Cast this solution on a Petri dish to a thickness of approximately 200 μm.
A uniform film was obtained.

Aluminum foil was tightly attached to both sides of this film, and while applying a 1000V DC electric field, the temperature was raised to 70°C and slowly cooled to 5°C.The electrodes of this film were removed and the Nd
When irradiated with -YAG laser (wavelength: 1.064 pm), the second light beam was about 10 times stronger than that of urea produced by the powder method.
Generation of harmonics (wavelength: 0.532 μm) was observed using a photomultiplier.

[Explanation of effects]

As described above, the nonlinear optical composition of the present invention is made from a para-disubstituted benzene derivative and a paraoxyalkylene that originally do not have a nonlinear optical effect.
), it has become possible to obtain thin films with good mechanical and optical strength, making it easier to apply nonlinear optical compositions to optical integrated circuits and optoelectronic integrated circuits. I made it a thing.

[Brief explanation of the drawing]

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. Third
The figure is a diagram illustrating the composition dependence of the nonlinear optical effect. FIG. 4 is a diagram illustrating the electric field dependence of the nonlinear optical effect. Figure 1 Figure 3 Dielectric compound composition m01' Figure 4

Claims (4)

[Claims] (1) A nonlinear optical material characterized by containing a compound represented by the following general formula (2) in a polyoxyalkylene matrix. General formula (2) ▲There are mathematical formulas, chemical formulas, tables, etc.▼ (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,
Nonlinear optics according to claim 1, which is an alkoxy group, an alkylamino group, a hydroxyalkylamino group, a dialkylamino group, a hydroxyalkyl-alkylamino group, a dihydroxyalkylamino group, a mercapto group, a hydroxy group, or a proton group. material. (3) the electron-withdrawing substituent is a nitro group, a cyano group, a halogen atom, a trifluoromethyl group, a carboxyl group,
The nonlinear optical material according to claim 1, which is a carboxyester group, a carbonyl group, or a sulfonyl group. (4) For nonlinear optical materials containing a compound represented by the following general formula (2) in a polyoxyalkylene matrix, general formula (2) ▲There are mathematical formulas, chemical formulas, tables, etc.▼ (where A is an electron (donating substituent; B indicates electron-withdrawing substituent) A method for aligning a nonlinear optical material in which the material is heated above its melting point and cooled to below its melting point while applying a DC electric field.