JPH01231386A - Optical switch device - Google Patents

Abstract

PURPOSE:To increase contrast ratio by constituting an optical switch device with a reflector which is provided with nonlinear optical input/output characteristic and whose reflectance changes on receiving controlled light, and a gain medium which composes external resonator structure together with the reflector. CONSTITUTION:An optical switch device is formed by a reflector such as a nonlinear optical etalon which is provided with nonlinear optical input/output characteristic and whose reflectance varies on receiving controlling light 5, and a laser amplifier 8 which is a gain medium of a semiconductor laser, etc., which composes external resonator structure together with the reflector. Since a laser oscillator is constituted as a whole by combining a gain medium with a reflecting mirror whose reflectance can be controlled by external controlling light 5, the reflectance of nonlinear optical etalon changes in accordance with external light. Laser oscillation of a gain medium combined with an etalon is thereby ON-OFF controlled, and consequently, the contrast ratio of the optical switch device can be substantially increased.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an optical switching element used in optical information processing, optical communication, etc., and particularly relates to improving the contrast ratio thereof.

[Conventional technology]

FIG. 2 is a structural schematic diagram showing a conventional optical switch shown in, for example, Applied Physics Magazine, Vol. 46, No. 10, 1985, pp. 918-920. 3 is a high reflectance dielectric film, 4 is a probe light, and 5 is a control light. Further, 6 is transmitted output light.

Next, the operation will be explained.

The transmittance T of the Fabry-Perot etalon configured using the dielectric film 3 as a reflecting mirror and the multiple quantum well layer 1 as a medium is expressed as follows. Here, RF is the reflectance of the dielectric film 3, φ.

is the initial phase of the etalon, n2 is the nonlinear refractive index coefficient of the multi-quantum well layer 1, Io is the power density of the control light 5, and λ. is the wavelength of the control light 5, and α is the absorption coefficient of the control light 5 in the multiple quantum well layer 1.

Contrast ratio (CR) is No = when there is no control light.
O) transmittance T. When FF and control light enter (L ≠0
) transmittance T. This is the ratio to N.

That is to say. Here φ. = 0. From this equation, it can be seen that in order to increase CR, it is sufficient to increase Δφ8, that is, Io.

[Problem to be solved by the invention]

Conventional optical switching elements are configured as described above, so the contrast ratio is a ratio of transmittance, and in order to obtain a large contrast ratio, it is necessary to increase the power of the input light (control light). .

However, when the input optical power is increased, the switching power increases, and the contrast ratio becomes saturated due to heat generation.

This invention was made to solve the above-mentioned problems, and an object thereof is to obtain an optical switch element that can significantly improve the contrast ratio.

[Means to solve the problem]

The optical switch element according to the present invention includes a reflector such as a nonlinear optical etalon that has nonlinear optical input/output characteristics and whose reflectance changes upon receiving control light, and a semiconductor that constitutes an external resonator structure together with the reflector. It consists of a gain medium such as a laser.

[Effect]

In this invention, since the laser oscillation device is constructed as a whole by combining a gain medium and a reflector whose reflectance can be controlled by external control light, the reflectance of the nonlinear optical etalon changes depending on external light. As a result, the laser oscillation of the gain medium combined with the etalon is 0N10FF.
As a result, the contrast ratio of the optical switch element can be greatly improved.

〔Example〕

An embodiment of the present invention will be described below.

FIG. 1 is a schematic diagram showing an optical switch element according to an embodiment of the present invention. In the figure, 1 is a multiple quantum well layer, 2 is a substrate, 3 is a high reflectance dielectric film, 4 is a probe light, and 5 is a 7 is a control light, 7 is a Bragg reflection layer, and 8 is a laser amplifier which is a gain medium of a semiconductor laser. Here, a multi-quantum well nonlinear etalon is constructed using a multi-quantum well layer 1 as a medium, a multi-quantum well layer 1, a high reflectance dielectric film 3. and a Bragg reflection N7, and this etalon and laser amplifier 8 constitute an external cavity type laser.

Next, the effects will be explained.

In such an external cavity type laser, if the reflectance of the high reflectance dielectric film 3 is RF and the reflectance of the Bragg reflective layer 7 at the Bragg center wavelength is R8, then the high reflectance dielectric film I!
13. Bragg reflective layer 7. The reflectance R of the etalon composed of the medium 1 and the medium 1 is expressed as follows. The meanings of the symbols used here are the same as in the conventional example. φ. Since generality is not lost even if =O, in the following, φ is used for simplicity. =0.

When control light 5 is OFF, No = 0), reflectance ROF
F becomes 4 West 717, and when the control light 5 is ON, N,≠0), the reflectance ROM becomes.

Therefore, the ratio of the reflectance when the control light is on and the reflectance when the control light is off is as follows.

Now, so that the laser is about to oscillate at reflectance R0, F,
By adjusting the current injected into the laser amplifier 8, it is possible to cause the laser to oscillate when the control light is incident and the reflectance becomes R2H.

That is, the threshold gain difference Δg before and after oscillation is expressed as l: the length of the laser amplifier, so if ROM/ROFF is appropriately large, a sufficient gain difference can be created, and the 0N10F of oscillation
F control becomes possible.

Furthermore, if a laser amplifier with high differential quantum efficiency and low spontaneous emission is selected, the power ratio of 0N10FF can be increased, thereby significantly increasing the contrast ratio of the optical switch element.

In the above embodiment, a reflection type etalon having a Bragg reflection layer 7 was used as the etalon, but it may be a transmission type etalon as in the conventional example. If it is fed back to the laser amplifier 8,
The same effects as in the above embodiment can be obtained.

Further, in the above embodiment, a multi-tl well linear etalon is used as a reflector having nonlinear input/output characteristics, but this may be a bulk crystal etalon, and the Bragg reflection layer may be another grating.

Furthermore, although the above embodiments have been explained in the case of an optical switch element, the basic principle of the present invention can also be applied to an optical bistable element.

〔Effect of the invention〕 .

As described above, according to the present invention, a reflector that has nonlinear optical input/output characteristics and whose reflectance changes upon receiving control light, and a gain medium that constitutes an external resonator structure together with the reflector. Since the optical switch element is constructed, the zero of laser oscillation is
Not only can N10FF be controlled by external light, but also an optical switch element with a high contrast ratio can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram for explaining an optical switch element according to an embodiment of the present invention, and FIG. 2 is a schematic structural diagram showing a conventional optical switch element. DESCRIPTION OF SYMBOLS 1...Multiple quantum well layer, 2...Substrate, 3...Dielectric film, 4...Probe light, 5...i! IJ? ff
1l light, 6... Transmitted light, 7... Bragg reflection layer, 8
... Gain medium 'If (laser amplifier), 9... Output light. Note that the same reference numerals in the figures indicate the same or corresponding parts. Agent Ken Hayase -ichihe0gu

Claims (1)

[Claims] (1) In an optical switch element whose emitted light is on/off controlled by control light, a reflector having nonlinear optical input/output characteristics and whose reflectance changes in response to the control light, and the reflector together with the reflector. An optical switch element comprising a gain medium constituting an external resonator structure.