JPH01285923A - Semiconductor light guide type optical switch - Google Patents

Abstract

PURPOSE:To enable switching of light regardless of the polarization direction of incident light by determining the direction of two semiconductor light guides which constitute a directional coupler and are parallel with each other by a specific method and providing electrodes to the light guides by a specific method. CONSTITUTION:The directions of the two semiconductor light guides A C E G I, B D F H J constituting the directional coupler attain 0-90 deg. angle with the [011] orientation in the [100] face PQRS of a semiconductor substrate 2 and 2 pieces of the electrodes 6 facing each other are provided to the 1st part CG,3 of the two semiconductor straight light guides parallel with each other in the direction [100] around the light guide 3 as the center. The 2nd part DH,3 of the semiconductor straight light guides is provided with >=2 pieces of the electrodes facing each other in the direction perpendicular to the direction of the electrodes 6 provided to the 1st part CG,3 around the light guide DH,3 as a center. The switching of the incident light is thereby executed regardless of the polarization direction of said light.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a polarization-independent semiconductor optical waveguide optical switch that does not depend on the polarization direction of signal light.

(Prior Art) As a conventional example of a directional coupler type optical switch constituted by a semiconductor optical waveguide having two-dimensional optical confinement, there is a document (K, Tada, H, Hayashi).

M, Tsuchiya and H, 5akaki
By E! xtendedAbstracts
of the 17th Conference on
5solidState Devices and M
material, Tokyo, 1985+pp
.

83-86). Such a conventional example will be explained based on FIG. 5.

FIG. 5 is a configuration diagram of a conventional example. In the figure, 11 is an ohmic electrode, 12 is an n'-GaAs substrate, 13 is n'-AIGaAs, 14 is n-GaAs, and 15 is n-A
IGaAs, and 16 is a Schottky electrode. 1
4 and 15 into a mesa stripe shape as shown in FIG.
An optical waveguide having two-dimensional optical confinement therein is formed. A directional coupler type optical switch is constructed by arranging two such straight optical waveguides in parallel and close to each other. By applying a reverse bias voltage via the Schottky electrode 16 on one optical waveguide, the phase of the TE mode, which has a polarization direction parallel to the surface of the ri'-GaAs substrate 12, of the propagating light is changed. Therefore, in the TE mode, it is possible to transfer the optical intensity from one waveguide to the other waveguide, that is, optical switching, by applying a voltage.

(Problem B to be solved by the invention) However, in the conventional example shown in FIG.
Optical switching in the TM mode, which has a polarization direction perpendicular to the surface of the As substrate 12, is impossible.

The present invention was proposed in order to improve the above-mentioned drawbacks, and its purpose is to eliminate the restriction on the polarization direction of incident light and provide a semiconductor optical waveguide type optical switch that does not depend on the polarization direction. There is a particular thing.

(Means for Solving the Problems) In order to achieve the above object, the present invention provides a directional coupling constructed by arranging two parallel semiconductor optical waveguides in close proximity to each other and having two-dimensional optical confinement. It is a box-type switch, and the directions of the two mutually parallel semiconductor optical waveguides constituting the directional coupler make an angle of 0 degrees or 90 degrees with respect to the (10 to 1 in the 1001 plane) orientation of the semiconductor substrate. None, two or more electrodes facing each other in the (100) direction with the optical waveguide as the center are provided in the first part of two mutually parallel semiconductor linear optical waveguides constituting the directional coupler. , the second part of the two mutually parallel semiconductor straight optical waveguides constituting the directional coupler has two or more mutually opposing electrodes provided in the first part with the optical waveguide as the center. The gist of the invention is a semiconductor optical waveguide type optical switch characterized in that two or more electrodes facing each other are provided in a direction perpendicular to the direction.

Therefore, the present invention is constituted by a semiconductor optical waveguide,
This is a directional coupler type optical switch that controls the propagation direction of light by applying a voltage, and its most important feature is that it can effectively switch light regardless of the polarization direction of incident light.

In a conventional directional coupler type optical switch using a semiconductor optical waveguide, there was a limitation that the polarization direction of the incident light must be in the TE mode parallel to the substrate surface, but in the optical switch of the present invention, the polarization direction of the incident light must be in the TE mode parallel to the substrate surface. This method differs significantly from conventional techniques in that there is no restriction on the direction of polarization, and effective optical switching is possible for incident light having any polarization component.

(Function) The directional coupler type optical switch of the present invention is composed of a semiconductor optical waveguide with two-dimensional optical confinement,
Light switching can be performed regardless of the polarization direction of the incident light.

(Example) Next, an example of the present invention will be described. Note that the embodiments are merely illustrative, and it goes without saying that various changes and improvements can be made without departing from the spirit of the present invention.

FIG. 1 is a diagram illustrating an embodiment of the optical waveguide type optical switch of the present invention. In the figure, square PQR3 is made of GaAs
Or it is the (100) plane of a zinc blend crystal with 43m symmetry such as InP, and PQ and R3 are <011
> is a cleavage plane perpendicular to <011>, and QR and SP are cleavage planes perpendicular to <011>.

A semiconductor optical waveguide with two-dimensional optical confinement is A-+C-+E-+G→1 or B-+D→F in FIG.
-H-+J. Between 00 and DH, two straight optical waveguides are arranged in parallel and close to each other to form a directional coupler type optical switch. The straight optical waveguide between 00 and DH is arranged to form a specific angle θ with respect to the straight optical waveguide which is parallel to the cleavage plane PQ from the input ends A and B provided on the cleavage plane SP. has been done. Here, θ is θ-0 degrees or 90 degrees. AC, BD, G
l.

The HJs are connected using smooth curved optical waveguides. The area between 00 and DH constituting the directional coupler type optical switch is divided into two areas, area 1 and area 2, and the lengths of each area are Ll and L2. Electrodes facing each other are provided on both sides of the optical waveguide in region 1. An electrode is provided on the optical waveguide in region 2.

FIGS. 2 and 3 show cross-sectional structures at KL and MN in FIG. 1, respectively. In Figure 2, 2 is (
100), 4 is an epitaxial film on the substrate 2, and 3 is a semiconductor optical waveguide formed in the epitaxial film 4 and having a larger refractive index than the epitaxial film 4. 5 is a high carrier concentration region for obtaining an ohmic junction, and has the function of applying a voltage to the optical waveguide 3 in a direction parallel to the (109) plane. 6 is an ohmic electrode.

On the other hand, in FIG. 3, 5 is a high carrier concentration region that serves to apply an electrode to the optical waveguide 3 in a direction perpendicular to the (100) plane, and 1 is an ohmic electrode provided on the back surface of the semiconductor substrate 2. , 4 is an epitaxial film, and 6 is an ohmic electrode.

Next, the operation will be explained.

Region 1 is placed on one side of the straight optical waveguide constituting the directional coupler.
When a voltage is applied in a direction parallel to the (100) plane through an electrode of , the polarization direction propagating through the optical waveguide changes to (10
0) TE mode light parallel to the plane and polarization direction is (100)
It is possible to change the phase of any light in the 7M mode perpendicular to the plane. However, the value of the ratio of the amount of phase change in the 7M mode to the amount of phase change in the TE mode is J'.

Next, by applying a voltage in the direction perpendicular to the (100) plane through the electrode having the length L2 of region 2, it is possible to change the phase of only the TE mode. At this time, the phase of the 7M mode does not change. Therefore, by applying voltage in region 1, the phase changes in 7M mode is 71 times larger than in TE mode, but by applying an appropriate voltage in region 2, the amount of phase change in TM and TE modes is made equal. It is possible to do so. Therefore, the lengths of the two types of electrodes in regions 1 and 2 provided in the directional coupler type optical switch are L I+L2
Alternatively, by appropriately selecting the magnitude of the voltage applied to each, a directional coupler type optical switch can be constructed.
The phase difference between the straight optical waveguides can be arbitrarily changed regardless of the polarization direction of the propagating light. Therefore, the directional coupler type optical switch enables optical switching that does not depend on the polarization direction of propagating light.

As is clear from the above description, the directional coupler type optical switch of the present invention is constructed of a semiconductor optical waveguide with two-dimensional optical confinement, and the optical switch is capable of transmitting light regardless of the polarization direction of the incident light. It is possible to perform switching.

FIG. 4 shows another embodiment of the present invention, in which the electrodes belonging to regions 1 and 2 are each divided into two. However, in a directional coupler type optical switch in which two straight optical waveguides are arranged close to each other in parallel, if the length of the parallel part is not exactly equal to the coupling length specific to the directional coupler, It is impossible to realize a complete optical switch by applying voltage with a single electrode. On the other hand, when the electrode is divided into two parts, complete optical switching can be achieved by reversing the applied voltages.

(Effects of the Invention) According to the present invention, in a directional coupler type optical switch, the directions of the two parallel semiconductor optical waveguides constituting the directional coupler are aligned with the floo) plane of the semiconductor substrate. The first part of the two parallel semiconductor straight optical waveguides forming the directional coupler is at an angle of 0 or 90 degrees with respect to the [0-1] direction. Two or more electrodes facing each other in the [100] direction are provided in the second portion of the two parallel semiconductor linear optical waveguides forming the directional coupler. By providing two or more electrodes facing each other in a direction perpendicular to the direction of the two or more mutually facing electrodes provided in the first part, the polarization direction of the incident light is independent. Since it is capable of switching the light and is entirely composed of semiconductor optical waveguides with two-dimensional optical confinement, it is important as an element of optical integrated circuits for optical information processing or optical communication. It has a certain effect.

[Brief explanation of the drawing]

FIG. 1 shows an embodiment of the semiconductor optical waveguide type optical switch of the present invention, and FIGS. 2 and 3 show -L in FIG. 1, respectively.
, FIG. 4 shows another embodiment of the present invention, and FIG. 5 shows a conventional example. ■, 6... Ohmic electrode 2... (100) Regenerative conductor substrate 3... Optical waveguide 4... Epitaxial film 5 with a lower refractive index than 3... High carrier Concentration region patent applicant Nippon Telegraph and Telephone Corporation

Claims (1)

[Claims] A directional coupler type switch configured by arranging two parallel semiconductor optical waveguides close to each other with two-dimensional optical confinement, which constitutes a directional coupler. The directions of two semiconductor optical waveguides parallel to each other form an angle of 0 degree or 90 degrees with respect to the [0@1@1] direction in the {100} plane of the semiconductor substrate, and the directions of the two semiconductor optical waveguides that are parallel to each other form a 0 degree or 90 degree angle with respect to the [0@1@1] direction. In the first part of two parallel semiconductor straight optical waveguides,
Two or more electrodes facing each other in the [100] direction with the optical waveguide as the center are provided, and the second portion of the two parallel semiconductor straight optical waveguides forming the directional coupler is provided with the A semiconductor optical waveguide characterized in that two or more electrodes facing each other are provided in a direction perpendicular to the direction of the two or more mutually facing electrodes provided in a first portion with the optical waveguide at the center. type optical switch.