JPH03209443A - Nonlinear optical element - Google Patents

Abstract

PURPOSE:To obtain the nonlinear optical element which has a large quadratic nonlinear optical constant and has the good compatibility with a high-polymer material by constituting this optical system of a medium having a specific hydrazine compd. CONSTITUTION:The hydrazine compd. which is the powder or crystal expressed by formula I is incorporated into the medium. In the formula I, R1 denotes an electron-donating substituent or electron-withdrawing substituent; X denotes CH or N atom. The hydrazine compd. expressed by the formula I has an n conjugation system in the molecular skeleton and has an electron-donating group or electron-withdrawing group as the substituent R1. The nonlinear optical element having the large quadratic nonlinear optical constant (beta value) and the good compatibility with the high-polymer material is obtd. in this way.

Description

DETAILED DESCRIPTION OF THE INVENTION "Field of Industrial Application" The present invention relates to organic nonlinear optical elements, and particularly to nonlinear optical elements using hydrazine compounds having excellent second-order nonlinear optical effects.

"Conventional technology" In the field of optoelectronics, as the wavelength of laser light has become shorter, existing laser light has been doubled in frequency (second
development of nonlinear optical materials that convert harmonics into light;
The development of nonlinear optical materials that exhibit large nonlinear optical effects and respond at high speed is being actively pursued. Traditionally, inorganic materials have been the main focus of development, but organic compounds are expected to have large nonlinear optical constants, fast response speeds, and low optical damage. For these reasons, organic compounds with π-electron conjugated systems have attracted attention (CMC, Organic Nonlinear Optical Materials R&D
No. 72, Masao Kato, Hebe Nakanishi (1985)
etc). According to these, as represented by 2-methyl-4-nitroaniline (hereinafter abbreviated as MNA), π
It is known that compounds having an electronic system and having an electron donating group and an electron withdrawing group in the molecule have a large second-order nonlinear optical constant β (hereinafter simply abbreviated as "β value").

However, as typified by 4-dimethylamino-4'-nitrostilbene (hereinafter abbreviated as DANS),
Even if the β value is large, because of the crystal structure with a center of symmetry,
It also has the disadvantage of not producing second-order nonlinear optical phenomena (
J., L., Oudar, J., Chem.

Phys, 87.446 (+977)) - Furthermore, the molecular arrangement in organic molecular crystals is often uniquely determined by individual molecular species in a certain temperature range, and it is extremely difficult to control the molecular arrangement in the crystal. Have difficulty. For these reasons, there have been few reports of organic compounds that exhibit higher second-order nonlinear optical effects than MNA, and therefore,
There are not many known elements with higher efficiency than nonlinear optical elements using MNA.

On the other hand, due to the above-mentioned problems, there is a method for producing a second-order nonlinear optical effect in an organic compound that does not exhibit a second-order nonlinear optical effect due to its crystal structure, despite exhibiting a large β value. have been variously studied (D, S, C
hela, J, Zyss, Non11nearOpti
cal Properties of Organic
Molecules and Crystals, Ac
academic Press, Inc., New York
k(+987)) *One of the methods is to use a liquid crystal compound or a liquid crystal polymer material as a medium. In other words, the molecular orientation of liquid crystal materials can be controlled by electric or magnetic fields in the liquid crystal state. Taking advantage of this property, an organic compound with a large β value is mixed into the liquid crystal material and an electric or magnetic field is applied. This is a method in which the organic compound is aligned in the alignment direction of the liquid crystal by applying an electric current, thereby eliminating the center of symmetry. For example, by mixing DANS into a liquid crystal polymer,
Generation of second harmonics has been observed in polymeric media obtained by applying an electric field and rapidly cooling the liquid crystal state (D,
j.

Williams+ Non1inear 0pti
cal Properties of Organic
Molecules and Crystals, p4
05, AcadeI! 1icPress, Inc., N
ew York (+987)).

Another method is to use a thermoplastic transparent polymer material as a medium. That is, as a polymeric medium,
Method using polymethyl methacrylate (K, D, S
inger, J.E., 5ohn, S.J., Lalama.
, Appl.

Phys, Lett, 49, 248 (1986)),
Method using acrylamide (JP-A-62-87139
There are methods using polyethylene glycol (Japanese Unexamined Patent Publication No. 64-522.523), and in these methods, as in the case of the liquid crystal material medium, the glass transition point of the polymer medium is Applying an electric field under the above heating condition,
This is a method of orienting organic compounds and eliminating the center of symmetry.

An even newer method is the method developed by Miyata et al. That is, it is a method using polyε-caprolactone as a polymeric medium (Ken Miyazaki, Toshiyuki Watanabe, Seizo Miyata,
Proceedings of the 35th Applied Physics Union Lecture Conference, p 179
(1989)), with this method, generation of second harmonics has been observed even without applying an electric field.

In addition, some hydrazine compounds (having -NHNH- bonds) that exhibit second-order nonlinear optical effects are known (J, F, N1coud, R, J.

Twleg, Non1inear 0ptica
l Properties of Organic M
o1ecules and Crystals, v
ol 2 p221, Academic Press
, Inc., New York (1987)), 4-nitrophenylhydrazine is the 1.
The nonlinear optical effect is not satisfactory, since the second harmonic is generated at six times the intensity.

``Problems to be Solved by the Present Invention'' Although the conventional organic nonlinear optical materials described above have very large nonlinear optical constants, they also have problems such as difficulty in obtaining large crystals, poor stability of the crystals, and phase problems with polymer materials. It has problems such as poor solubility. Furthermore, the nonlinear optical constants are still not satisfactory.

SUMMARY OF THE INVENTION In order to overcome these problems, the present invention provides a nonlinear optical element using an organic compound that has a large second-order nonlinear optical constant and is highly compatible with polymeric materials.

"Means for Solving the Problems" The above problems can be achieved by using a hydrazine compound represented by the following general formula (1).

That is, a nonlinear medium comprising at least a compound represented by "wherein R1 represents an electron-donating substituent or an electron-withdrawing substituent, and X represents a CH or N atom" It is placed between optical elements.

The present invention has the above configuration, and the hydrazine compound represented by the general formula (1) has a π-conjugated system in the molecular skeleton, and an electron-donating group or an electron-donating group as the substituent R1. has. Furthermore, the longer the π-electron conjugated system and the stronger the electron-withdrawing property of the substituent, the larger the second-order nonlinear optical constant (β value) becomes. Also,
The hydrazine compound represented by the general formula (1) consists of a rigid π-electron conjugated system part and a hydrazine part with high flexibility, and is compatible with liquid crystal polymers, other polymer compounds, or liquid crystal compounds. Excellent compatibility. Therefore, in a nonlinear optical element using a mixture of a hydrazine compound represented by the general formula (1), a liquid crystal polymer, another polymer compound, or a liquid crystal compound, the general formula (1) is used as the organic nonlinear compound. ) When using a hydrazine compound represented by
Since this content can be increased, a high nonlinear optical effect can be obtained.

Note that the second-order nonlinear optical constant (β value) of an organic compound is
P P P (Pariser-Parr-Pople
) -Mo method is known to be able to perform theoretical calculations, and β values can be calculated using each molecular parameter obtained by the PPP-Mo method (j, L, 0u
dar1.1. Chem, Phys, 67.446 (
+977)).

Using the method of Oudar above, a compound represented by general formula (1), R1: p-c)(, o X :C
When the β value of the compound represented by H (compound I-7 below) was calculated, it was a very large value of 371X IQ-"esu. Similarly, when the β value was calculated for MNA and DANS, Each 14.9X 10-”e
su and 280X 10-30. In addition, in the measurement results of the above compound using the powder method, a considerably stronger second harmonic was observed compared to MNA, and when estimating the β value of the compound,
The validity of using the P P P-Mo method is demonstrated.

Therefore, using this method, we estimate the β value of the molecule1,
After predicting the optimal molecular structure from the standpoint of molecular design, actually measuring and evaluating it using methods such as the powder method, and adding various considerations, we found that the hydrazine compound represented by general formula (1) is effective. It became clear. The present invention has been made based on this knowledge, and is characterized in that a nonlinear optical element constituted by a medium into which light is incident is characterized in that the subject body contains a hydrazine compound represented by the following general formula (1). It is used between nonlinear optical elements.

The above hydrazine compound has the following structure.

! )'"However, R1 represents an electron-donating substituent or an electron-withdrawing substituent, and X represents a CH or N atom. The substituent represented by JR1 is not particularly limited, and may be an electron-donating substituent or electron-withdrawing substituents. Examples of these include alkyl groups, (CHs) 2N -CH5N H-H
2N-PhNH- (Ph is a phenyl group).

CH, CONH-CH, 0CONH-CH, ○-PhO
-H, -Halogen, -CH2X (X is a halogen atom), -COOH, -COOR (R is an alkyl group), -C
OOPh, -COR.

'COP h, -CON H2, -CONR2
,-CN.

-NO3, -C=CH, -CH=CHC0OH.

-CH=CHCN, -CH=C(CN)2゜-C
Examples include substituents such as H=NPh.

The compound represented by the general formula (1) is described, for example, in the US Patent Application Specification, App1. No, 274.223 (
1988, 11, 21> etc. Hereinafter, typical examples of the compound represented by the general formula (2) will be shown, but the present invention is not limited to these examples.

/ The nonlinear optical element of the present invention may be a crystal or powder consisting of a single component of the compound represented by the general formula (I), or may be a crystal or powder consisting of a single component of the compound represented by the general formula (I). It may be a solid material made of a thermoplastic transparent polymer, a liquid crystal polymer, or a mixture with a liquid crystal compound. By using a solid mixture of the compound represented by the general formula (I) and a thermoplastic transparent polymer, liquid crystal polymer, or liquid crystal compound, the compound represented by the general formula (1) can be obtained by utilizing the molecular orientation of these media. It is possible to control the molecular orientation of the compound used, and it is possible to obtain larger nonlinear optical effects. Furthermore, these media have the advantage that they have high film formability and can be easily formed into devices such as thin films.

The transparent polymer used in the present invention is not particularly limited, but examples include polymethyl methacrylate, polyacrylamide, polyethylene glycol, polyoxyalkylene oxide, polyvinylidene fluoride, polyε-caprolactone, etc. It is.

The liquid crystal polymer used in the present invention is not particularly limited, but, for example, a side chain type liquid crystal polymer having a mesonigenic group in the side chain is preferable. Examples include side chain type polyacrylate liquid crystal polymers and side chain type polysiloxane liquid crystal polymers.

The liquid crystal compound used in the present invention is not particularly limited, but for example, a compound having a liquid crystal transition point higher than room temperature is preferably used.

Crystals consisting of a single component of the compound represented by the general formula (1) can be obtained by heating and melting the compound represented by the general formula (I), cooling it, and crystallizing it (Bridgeman method, Ralski method, etc.), a method of melting in an appropriate solvent (for example, methanol, ethanol, tetrahydrofuran, benzene, toluene, etc.) at an appropriate temperature, and then lowering the temperature or gradually removing the solvent, etc. It can be obtained by a method of crystallization, a vacuum evaporation method, a vapor phase growth method such as molecular beam epitaxy, or the like.

In addition, a solid mixture of a compound represented by general formula (1) and a thermoplastic transparent polymer, a liquid crystal polymer, or a liquid crystal compound is a solid mixture of a compound represented by general formula (1), a thermoplastic transparent polymer, or a liquid crystal compound. After melting a polymer or a mixture with a liquid crystal compound, in the case of a thermoplastic transparent polymer, it is in that state, and in the case of a liquid crystal polymer or a liquid crystal compound, it is gradually cooled in the liquid crystal state obtained by applying an electric field. Alternatively, it can be obtained by applying a magnetic field and cooling and solidifying in that state. By applying an electric field or a magnetic field, the compound represented by the general formula (1) is solidified while maintaining the molecular orientation without a center of symmetry according to the orientation of the polymer or liquid crystal material. The mixing ratio of each component is
The compound represented by the general formula (I) is not particularly limited as long as it can take a solid state with molecular orientation. Since the compound represented by the general formula (1) has excellent compatibility with these media, it can be selected from a wide range. If the content is too low, a sufficient nonlinear optical effect cannot be obtained, and if it is too high, it becomes difficult to control the molecular orientation using the medium. Usually, the content of the compound represented by the general formula (I) is 2 to 2. A range of 60% is preferably used.

Furthermore, the nonlinear optical element of the present invention can take various forms, such as crystals or powder consisting of a single component of the compound represented by the general formula (1), or a crystal or powder represented by the general formula (I). A solid material (hereinafter referred to as
(hereinafter collectively referred to as a nonlinear medium) can be used as a nonlinear optical element, and furthermore, the nonlinear medium can be used as a waveguide-type nonlinear optical element that uses the nonlinear medium as an optical waveguide. In the latter case, since light can be confined within the waveguide, higher efficiency can be achieved, such as increased optical power density and longer interaction length. Furthermore, phase matching becomes easier.

"Examples" The present invention will be explained in more detail using Examples below.
The present invention is not limited by these examples. FIGS. 1 and 2 are examples of the nonlinear optical element of the present invention, and show schematic diagrams of an optical waveguide type wavelength conversion element as a second harmonic generation element. Figure 1 shows that the core (4) is made of a medium containing a hydrazine compound represented by the general formula (1) that has a second-order nonlinear optical effect, but does not exhibit a second-order nonlinear optical effect, such as glass. It has a structure covered with a cladding (5) made of a medium (hereinafter abbreviated as an isotropic medium).In the figure, the solid line indicates the fundamental wave of the incident light, and the dotted line indicates the second harmonic. Laser light is transmitted through lenses, etc.
3) and enters the core (4) from one end of the element. A second harmonic is generated within the core, and the second harmonic including the fundamental wave is emitted from the other end.The second harmonic can be extracted by dispersing it with a spectroscopic means such as a prism or filter. can.

FIG. 2 shows a cross-sectional view of the device, in which a waveguide (8) containing a hydrazine compound represented by the general formula (1) having a second-order nonlinear optical effect is connected to a low refractive index layer (9). It has a structure in which it is sandwiched between electrodes (6) and (7). These layers are formed on a substrate (10) consisting of an isotropic medium. In the figure, the low refractive index layer (9
) is composed of a $1 thin film such as vinylidene fluoride-trifluoroethylene copolymer or an inorganic thin film such as 5i02. In the figure, the solid line indicates the fundamental wave of the incident light, and the dotted line indicates the second harmonic. The laser light is focused by a lens or the like (3), and enters the waveguide (8) from one end of the element. A second harmonic is generated within the waveguide, and the second harmonic including the fundamental wave is emitted from the other end, and the second harmonic is extracted by dispersing it with a spectroscopic means such as a prism or filter. I can do it.

Furthermore, it can also be used as a conventionally known optical modulation element. FIG. 3 is an example of a light modulation device, and shows a schematic diagram of an optical waveguide type light modulation device, in which a hydrazine system represented by the general formula (I) is contained in a substrate (13) made of an isotropic medium. A waveguide (12) made of a medium containing a compound is provided, and two electrodes (11) are provided at opposite positions along the length of the waveguide (12). 11) An electric field is formed by applying a voltage between them using an external electric field (14). In the above element, when the laser beam incident from one end of the waveguide passes through the waveguide (12) and is emitted from the other end, the refractive index of the nonlinear medium changes due to the electric field, and therefore, The phase of the emitted light also changes, allowing phase modulation.

In the figure, (1) indicates a laser light source, (2) indicates an optical modifier such as an optical switching element or an optical polarizer, and (
3) represents a condensing lens.

In the nonlinear optical elements shown in FIGS. 1, 2, and 3 above, the core (4) or the waveguide (8), (
12) are formed on substrates (10) and (13) made of a capillary or an isotropic medium such as glass or plastic according to the crystal growth method described above. Furthermore,
If necessary, the nonlinear optical element may be formed by treating the contact interface with the nonlinear medium with an alignment treatment material, and then depositing the nonlinear medium. In FIGS. 2 and 3, conductors such as indium tin oxide (ITO), tin oxide, indium oxide, gold, silver, copper, and aluminum can be used as the electrodes.

It should be noted that the nonlinear optical element of the present invention is not limited to the above-mentioned embodiments, and can take various forms, and may be composed of crystals, powders, etc. Furthermore, in the optical modulation element shown in FIG. 3, the direction of applying the electric field for performing phase modulation varies depending on the symmetry of the nonlinear medium, the direction of the crystal axis, etc., and the configuration of the electrodes is changed as appropriate based on these factors. There is a need.

Hereinafter, the present invention will be described in detail based on Examples,
The present invention is not limited to the following measurement examples.

Example 1 1064 of a hydrazine compound represented by general formula (1)
Theoretical calculation of the β value for a nm laser beam was performed using the PPPMO method. The results are sent to MNA, DANS
A comparison is shown in Table 1.

Example 2 Crystals of the hydrazine compound represented by the general formula (1) were crushed and filled into a 0.1 mm thick glass cell. When this cell was irradiated with Nd:YAG laser light (wavelength 101064n), the second harmonic (532nm) was observed.

Table 2 shows the intensity of the second harmonic, which is classified into three levels: the same level, considerably stronger, and stronger than MNA.

Table 11.2 of t/Example 3 0.4 g of the compound represented by 1-7 or ll-7 and 2 g of polyoxyethylene with a molecular weight of 5 million were mixed with benzene 5
ml was heated and melted and spin-coded onto a glass substrate on which aluminum had been vacuum-deposited, and evaporated to dryness while keeping the temperature at 80°C to obtain a uniform film. Furthermore, aluminum was vacuum-deposited thereon to obtain a waveguide type nonlinear optical element. This device was cooled to room temperature while maintaining the temperature at 80° C. and applying a 1000 V electric field to the upper and lower aluminum electrodes. In this nonlinear optical element, Nd:YAC
When laser light (10B4 nm) was focused and irradiated, a fairly strong second harmonic (532 nm) was observed.

"Effects of the Invention" As described above, the nonlinear optical element of the present invention has the following formula (1):
The hydrazine compound represented by the general formula (I) has a large nonlinear optical constant (β value) and exhibits a remarkable second-order nonlinear optical effect. Therefore, the nonlinear optical element of the present invention has the characteristics that it can separate high-intensity second harmonics even with weak light, and can efficiently express the electro-optic effect even with small voltage changes. The hydrazine compound represented by formula (I) has excellent compatibility with thermoplastic transparent polymers, liquid crystal polymers, or liquid crystal compounds. The nonlinear optical elements contained include nonlinear optical elements such as wavelength conversion elements, second harmonic display parametric oscillators, and optical switches, and optical communication systems using them.
It is useful for constructing optical information processing.

[Brief explanation of drawings]

1 and 2 are schematic diagrams of a wavelength conversion element as an embodiment of the nonlinear optical element of the present invention, and FIG. 3 is a schematic diagram of a light modulation element. (1) Laser light source (2) (3) (4) (5) (6) (7) (8) (9) (l 0) (11) (l 2) (l 3) (l 4) Modulator Lens core cladding upper electrode lower electrode nonlinear optical waveguide low refractive index layer substrate electrode nonlinear optical waveguide substrate external electric field

Claims (3)

[Claims] (1) A nonlinear optical element comprising a medium into which light is incident, wherein the medium contains a hydrazine compound represented by the following general formula (I). ▲There are mathematical formulas, chemical formulas, tables, etc.▼ (I) ``However, R1 represents an electron-donating substituent or an electron-withdrawing substituent, and X represents a CH or N atom.'' (2) The nonlinear optical element according to claim 1, wherein the medium is a powder or crystal of the hydrazine compound. (3) The nonlinear optical element according to claim 1, wherein the medium is a transparent polymer or a liquid crystal compound containing the hydrazine compound.