JPH05307202A - Nonlinear optical element - Google Patents

Abstract

PURPOSE:To enable the taking out of a change in refractive index by a cubic nonlinear optical effect with a high sensitivity by forming a nonlinear optical material which has cubic nonlinearity and optical-rotatory dispersion characteristic. CONSTITUTION:This nonlinear optical material 21 has the cubic nonlinearity and optical- rotatory dispersion characteristic and its optical path length is set in such a manner that the plane of polarization rotates 90 deg. when reference light 22 of a wavelength lambda1 is transmitted therethrough as linearly polarized light in a perpendicular direction by a polarizer 24. Then, the reference light 23, the plane of polarization of which is rotated by 90 deg. to be in the horizontal direction is shut off by an analyzer 25 having the bearing in the perpendicular direction when control light 23 is not made incident. On the other hand, the control light 23 is strong light and, therefore, the light induces the nonlinear optical effect in the nonlinear optical material 21 when the control light 23 of a wavelength lambda2 is made incident as the linearly polarized light in the perpendicular direction on the nonlinear optical material 21 by the polarizer 24. Namely, the nonlinear optical effect is induced on the plane of polarization of the reference light 22 in the state where the plane of polarization of the reference light 22 inclines from the plane of polarization of the control light 23 and, therefore, the reference light 22 is eventually made into elliptically polarized light. A perpendicular component is, therefore, generated in the reference light 22 and is passed through an analyzer 25.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-linear optical material used in the fields of optoelectronics, optical information processing, optical communication and the like.

[0002]

2. Description of the Related Art Nonlinear optical materials are materials that exhibit a second-order or higher nonlinear response under a strong electric field of laser light, and are important materials in optical signal processing such as frequency conversion, oscillation, and switching. is there. In particular, the third-order nonlinear optical material has been attracting attention as a basic material for next-generation optical communication and information processing, which fully exhibits the excellent characteristics of light such as high speed and parallelism. A non-linear optical element using this third-order non-linear optical material intends to utilize that the refractive index changes with the irradiation of light.
Optical car shutters are known. The optical Kerr shutter performs light-light switching and light-light control by irradiating the nonlinear optical material with strong control light and changing the polarization state of the reference light that passes through the nonlinear optical material.

FIG. 1 shows a schematic view of an example of a conventional optical car shutter. Reference numeral 11 is a non-linear optical material in which CS ₂ is put in an optical cell. 14 is a polarizer setting the orientation in the vertical direction, the reference beam 12 with a wavelength lambda ₁ is the polarizer 1
4 causes the light to be polarized in the vertical direction. Therefore, the control light 13
When is not incident, the reference light is blocked by the analyzer 15 whose azimuth is set to the horizontal direction. On the other hand, the control light 13 having the wavelength λ ₂ is converted into linearly polarized light whose polarization plane is tilted by 45 ° by the polarizer 16 whose azimuth is tilted by 45 °, and the nonlinear optical material 11
When the light is incident on, the control light is a strong light and causes a nonlinear refractive index change in the nonlinear optical material 11. At this time, since the polarization plane of the control light is inclined with respect to the polarization plane of the reference light, the reference light becomes elliptically polarized light. Therefore, a horizontal component is generated in the reference light, which is transmitted through the analyzer 15. As described above, conventionally, in order to realize light-light switching, it is necessary to add a device such as tilting the polarization plane with respect to the reference light to the polarization of the control light, and also to make the analyzer orthogonal to the polarizer of the reference light. Therefore, it is necessary to prepare polarizers of various orientations, which causes a problem that the structure of the device is complicated.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems and to take out the change in refractive index due to the third-order nonlinear optical effect with high sensitivity by utilizing the optical rotatory dispersion characteristic of an optical rotatory substance. It is to provide a novel nonlinear optical element that can be used. The present invention is a non-linear optical element for controlling the polarization state of reference light with light having a wavelength different from the wavelength of reference light, wherein the non-linear optical material has third-order non-linearity and optical rotation dispersion characteristics. Regarding

The form of the nonlinear optical material of the present invention is as follows:
A substance doped with a substance having optical rotation dispersion property and a substance having third-order nonlinearity, a substance having a substance having optical rotation dispersion performance doped in a polymer having third-order nonlinearity, and conversely a substance having third-order nonlinearity And a polymer having optical rotatory dispersion performance.
Alternatively, it may be an aggregate of a substance having optical rotation dispersion performance and a substance having third-order nonlinearity. Another form of the nonlinear optical material of the present invention is one in which one substance has both optical rotatory dispersion performance and third-order nonlinearity. For example, a substance having optical rotatory dispersion performance in the side chain of a polymer and third-order nonlinearity. Introducing a substance having a compound having a third order non-linearity, or a substance having a third order nonlinearity in the side chain of a polymer having optical rotation dispersion performance, conversely, The ones introduced are listed. Of course, the substance itself having the third-order nonlinearity may have the optical rotation dispersion performance, and the origins of the third-order nonlinearity and the optical rotation dispersion performance in this case may be the same or different.
Furthermore, as another form of the nonlinear optical material of the present invention,
A plurality of layers including a layer containing a substance having optical rotation dispersion performance and a layer containing a substance having third-order nonlinearity may be alternately laminated.

Examples of the substance having the optical rotatory dispersion property include a chiral compound having the optical rotatory dispersion property, a substance exhibiting the optical rotatory dispersion property by crystallization, or an external electric field.
Examples thereof include substances exhibiting optical rotation dispersion performance due to a magnetic field or rubbing of a substrate. Examples thereof include amino acids, polypeptides, tartaric acid, helicene, crystals, cholesteric liquid crystals, nematic liquid crystals and the like. Examples of the substance having third-order nonlinearity include those having a large delocalized π-electron system, and examples thereof include DANSE (4-dimethylamino-4′-nitrostilbene) and tetrakis (2,4-xylyl). Butatriene, 9,10-bis (3,3-diphenyl-3-hydroxypropynyl) anthracene, 2- (4-nitrophenyl) -4,5-diphenylimidazole, 2- (4-nitrophenyl)-
4,5-bis (4-methoxyphenyl) imidazole,
Tetrathiotetracene, 3,6-bis (4,5-diphenyl-2H-imidazol-2-ylidene) -1,4-
Cyclohexadiene, 2- (thiopyran-4-ylidene) -1,3-dithiol, 1,1,6,6-tetraphenyl-hexa-1,5-diene-3yne, 3,3'-
Examples thereof include diethyloxacarbocyanine and 3,3′-diethyloxadicarbocyanine, and CuCl, CdSe, ZnSe and the like due to the effect of excitons.

In the present invention, the polarization state of the reference light incident on the nonlinear optical element is controlled by the light having a wavelength different from the wavelength of the reference light. That is, the reference light and the control light having different wavelengths incident on the same plane of polarization are rotatively dispersed by the nonlinear material.
Since an angle is generated between the polarization planes of the reference light and the control light inside the material, the control light can cause the polarization change of the reference light. Therefore, the light-light control element can be obtained with a simple polarizer configuration. Further, by setting the optical path length and the concentration so that the optical rotation angle with respect to the reference light is 90 ° + n × 180 ° (n is an integer), the optical-optical switching element is configured only by the polarizers in the same direction. be able to.

[0008]

EXAMPLES The present invention will be specifically described below with reference to examples. Example 1 FIG. 2 is a schematic diagram of an optical-optical switching device using the nonlinear optical element of the present invention. Reference numeral 21 denotes a non-linear optical material, which is a film obtained by dissolving poly-L-glutamic acid and DANSE in dichloroethane, casting, and removing the solvent. Reference numerals 24 and 25 denote polarizers whose azimuths are set in the vertical direction, where 24 serves as a polarizer and 25 serves as an analyzer. The nonlinear optical material 21 uses the reference light 2 having the wavelength λ ₁ .
The optical path length is set so that the plane of polarization is rotated by 90 ° when 2 is transmitted as vertical linearly polarized light by the polarizer 24. Therefore, when the control light is not incident, the reference light whose polarization plane is rotated by 90 ° and becomes horizontal is blocked by the analyzer 25 whose azimuth is vertical.

On the other hand, the control light 23 having the wavelength λ ₂ is supplied to the polarizer 24.
As a linearly polarized light in the vertical direction, the nonlinear optical material 21
When the light is incident on, the control light is a strong light and causes a nonlinear optical effect in the nonlinear optical material 21. At this time, since the control light and the reference light have different wavelengths, the rotation angle of the polarization plane is different due to the optical rotation dispersion. That is, the nonlinear optical effect is induced in the state where the polarization plane of the reference light is inclined with respect to the polarization plane of the control light, and as a result, the reference light becomes elliptically polarized light.
Therefore, a vertical component is generated in the reference light, which is the analyzer 25.
Through. As described above, according to the present invention, even if the reference light and the control light have the same polarization plane, by changing the wavelengths of the reference light and the control light to enter the nonlinear optical material, the optical rotatory dispersion performance and the third order An optical-optical switching device can be realized by utilizing the non-linearity. Example 2 4% C of (+)-hexahelicene as a nonlinear optical material
In an apparatus similar to that of FIG. 2 using S ₂ solution, 440n
The reference light of m and the control light of 535 nm were made incident on the same polarization plane, and the relationship between the intensity of the control light and the intensity of the detection light was investigated. As a result, as shown in FIG. 3, detection light proportional to the square of the intensity of the control light was obtained, and it was confirmed that the car shutter was operating.

[Brief description of drawings]

FIG. 1 is a schematic diagram of a conventional optical-optical switching device.

FIG. 2 is a schematic diagram of an optical-optical switching device according to an embodiment of the present invention.

FIG. 3 is a diagram showing a relationship between the intensity of control light and the intensity of detection light in the second embodiment.

[Explanation of symbols]

 11 Nonlinear Optical Material 12 Reference Light 13 Control Light 14, 16 Polarizer 15 Analyzer 21 Nonlinear Optical Material 22 Reference Light 23 Control Light 24 Polarizer 25 Analyzer

Claims (1)

[Claims] 1. A non-linear optical element for controlling the polarization state of reference light with light having a wavelength different from that of the reference light, wherein the non-linear optical material has third-order non-linearity and optical rotation dispersion characteristics. element.