JPH01239986A - Bistable semiconductor laser - Google Patents

Abstract

PURPOSE:To increase the degree of freedom in constituting an optical logic circuit by installing the following: a tandem electrode composed of two electrode pieces which are separated from each other; a beam-incidence window composed of a grating in a saturable region. CONSTITUTION:A bistable semiconductor laser is composed of the following: an InGaAsP 3; p-InP 4; n-InP 5; p-InP 6; p-InP 7; an InGaAsP active layer 8; an n-InP substrate 9; an n-electrode 10. A DFB laser of a DC-PBH structure is formed on the n-InP substrate 9 having a primary grating 11 by a liquid epitaxial growth method and by chemical etching. Then, a resist 20 is coated on the side of the p-electrode 2; the electrode 2 is formed; a beam-incidence window 13 is formed by a lift-off method.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a bistable semiconductor laser suitable for use as an optical processing device or the like.

(Prior Art) In recent years, research activities have been actively conducted on surface processing type semiconductor optical processing devices as next-generation semiconductor processing devices to replace semiconductor electronic processing devices. Among the operational elements using optical semiconductors, there is an optical bistable semiconductor element called 5EED.

This optical bistable semiconductor device is a multi-quantum well N (hereinafter referred to as M
It is an element formed by connecting a voltage source and a resistor in series to a pin diode having an I-type semiconductor layer (abbreviated as QW layer).

When a reverse voltage is applied perpendicularly to the MQW layer, this device
This is an optical bistable semiconductor device that utilizes the shift of band edge absorption (including the peak of exciton resonance) to the lower energy side. When the wavelength of the input light is selected near the exciton resonance when the reverse voltage is 0, and the light is incident on this element under the reverse voltage, a photocurrent flows. The flow of this photocurrent increases the voltage breakdown in the series-connected loads.

As a result, the voltage applied to the pin junction decreases, and the light absorption in the MQW layer increases accordingly, resulting in a feedback effect such as 6 or more that causes a larger voltage change, causing an optical twin in the light input/output relationship. Stability appears.

5EED is an element that operates bistablely based on the above principle (Applied Physics Letter Appli
ed Physics Letter Vol, 45
No, l 1st July 1984
PP13-15).

In addition to the above-mentioned surface-processed semiconductor devices, conventional semiconductor devices that are the key to optical exchange and optical computers include bistable lasers whose input and output surfaces are the laser light output surfaces of semiconductor lasers. . This bistable semiconductor laser has a non-excited region or a low-excited region in a part of the active region within the optical resonator, thereby making this part a saturable absorber. The bistable characteristic can be achieved by optical input-optical output or injection current-optical output (1984 National Conference of the Institute of Electrical Communication Engineers 1024).

If these bistable semiconductor lasers are used, a semiconductor optical arithmetic device that performs operations such as logical sum and logical product based on input signal light (or electrical input signal) using a preset laser threshold value etc. can be configured.

(Problems to be Solved by the Invention) In conventional bistable semiconductor lasers having such a function, when considering the input signal as light, the optical input section and the optical output section are all on the same axis.

Therefore, when conventional bistable semiconductor lasers are incorporated into optical computers, optical exchangers, etc. to form several stages of logic circuits, they are arranged only on one plane.
Freedom was severely restricted. As described above, the conventional technology has a problem in that the degree of freedom of arrangement is restricted.

(Means for Solving the Problems) A bistable semiconductor laser having tandem electrodes according to the present invention is characterized by having a light entrance window made of a grating in a saturable absorption region.

(Function) In the present invention, a grating for optical coupling is formed in the saturable absorption region of a bistable semiconductor laser, a light entrance window is provided by a lift-off method, and signal light is made incident through this window. This makes it possible to input signal light, which conventionally entered from the end face of the laser resonator, from the upper and lower surfaces of the bistable semiconductor laser. Input light is absorbed in the saturable absorption region by the optical coupling grating, and as a result, the gain state of the saturable absorption region shifts from the absorption side to the gain side, resulting in bistable operation.

(Embodiment) FIG. 1 is a sectional view showing an embodiment of the present invention, and the cut plane in this figure is on a plane perpendicular to the resonator axis at the laser emission end. 1
is InGaAsP oscillation region, 2 is p-electrode, 3 is P-I
nGaAsP, 4 is P-InP, 5 is n-InP, 6 is p-InP, 7 is p-1nP, 8 is InGaAsP active layer, 9 is n-InP substrate, 10 is n''?E'fI, The laser has a D C-P B H structure.

FIG. 2 is a diagram showing the manufacturing process of the first embodiment, and (a) to (c) of this figure are cross-sectional views of the laminated structure formed in each step when manufacturing the embodiment.

Each cross section in this figure is on a plane passing through the resonator axis and perpendicular to the bottom surface of the substrate 9. In figure 0, 11 is the grating of the DFB laser (first-order grating), 12 is the saturable absorption region, and 13 is the light incidence window. It is. A DFB laser with a DC-PBH structure is formed by liquid phase epitaxial growth and chemical etching on an InP substrate 9 having a first-order grating for the oscillation wavelength of the laser (FIG. 2(a)). ), then p-electron [211
A resist is applied to the saturable absorption region 12 of the TI, and an electrode is deposited (FIG. 2(b)). Then, a light entrance window 13 is formed by a lift-off method (FIG. 2(C)).

FIG. 3 is a schematic diagram showing the input and output of the embodiment shown in FIG.

In this figure, the embodiment is shown as a cross-sectional view of a plane passing through the resonator axis. 15 is the input signal light, 18 is the output signal light, and 19 is the input signal light.As shown in the figure, the input signal light is input through the entrance window 1.
It enters from 3.

FIG. 4 is a schematic diagram showing the input/output of another embodiment of the present invention. This embodiment is a Fabry-Perot laser, which has a grating only in the saturable absorption region and absorbs the incident light 15.

Further, FIG. 5 is a schematic diagram showing the input/output of still another embodiment of the present invention, in which the saturable absorber 1 in the structure of FIG.
The period of the grating on the InP substrate 8 in the part 2 is made longer than the current injection part6.
If a higher-order grating than the second-order is used as the grating for the part where the input signal is input, it is possible to input the input signal light 17 at an angle without significantly changing the intensity of the light compared to vertical input, and at the same time input the output signal light 16 vertically. You can also take it out from the surface.

This is possible due to the properties of its higher-order crating.

If the grating of the saturable absorber portion in the embodiment of FIG. 4 or FIG. At the same time, it is also possible to output the output signal light 14 from the vertical plane due to the characteristics of the secondary crating.

(Effects of the Invention) If the present invention is applied, it is possible to provide a bistable semiconductor laser in which an optical signal can be inputted from a direction perpendicular to the top surface of a substrate, and which has a large degree of freedom in arrangement when configuring an optical logic circuit. Therefore,
By employing the bistable semiconductor laser of the present invention, it is possible to solve the problem in conventional technology that when constructing multiple stages of logic circuits, the degree of freedom is extremely restricted because the devices are arranged on one plane. Can be done.

[Brief explanation of the drawing]

Fig. 1 is a sectional view of a laser emitting end in an embodiment of the present invention, Fig. 2 is a diagram showing the manufacturing process of the embodiment, Fig. 3 is a schematic diagram showing the manpower output of the embodiment, and Fig. 4 and FIG. 5 is a schematic diagram showing the input/output of another embodiment of the present invention. In the figure, 1 is the InGaAs P oscillation region, and 2 is the P oscillation region.
- electrode, 3 is p-1nGaAsP, 4 is p-InP, 5
is n-InP, 6 is p-InP, 7 is p-InP, 8 is InGaAsP active layer, 9 is n-InP substrate, 10 is n
- electrode, 11 is the grating of the DFI3 laser, 12
13 is a saturable absorption region, 13 is a light incidence window, 15.17 is an input signal light, 14, 16, 18 is an output signal light, 19 is an input signal light, and 20 is a resist.

Claims (1)

[Claims] A bistable semiconductor laser, characterized in that it has a tandem electrode made up of two electrode pieces separated from each other, and has a light entrance window made of a grating in a saturable absorption region.