JPH0578808B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an optical bistable circuit for optical logic circuits and optical storage circuits.

(Prior Art and Problems) Research and development is progressing on various optical circuits aimed at signal processing using light. An optical bistable circuit is a basic optical circuit constituting these optical circuits, especially optical logic circuits and optical storage circuits. This is an optical circuit that can provide two stable optical output levels for a given optical input. Conventionally, as such an optical bistable circuit, there is a bistable semiconductor laser in which a gain region and a saturable absorption region are arranged in series in the cavity axis direction of the semiconductor laser. This bistable semiconductor laser has several desirable features, such as a relatively large optical output level of several milliwatts and a response speed of less than 1 nanosecond. However, this bistable semiconductor laser had a problem in that it required a rather large optical trigger input to trigger it into the on state. In particular, when the pulse width of the optical trigger input is made smaller in order to use it for high-speed signal processing, the problem that the input trigger level increases rapidly is unavoidable.

(Object of the Invention) An object of the present invention is to provide an optical bistable circuit that can operate with a low optical trigger input.

(Structure of the Invention) According to the present invention, there is provided a bistable semiconductor laser having an amplification region and a saturable absorption region, an optical waveguide optically coupled thereto and installed in parallel, and an optical amplifier coupled to the optical waveguide. A low trigger level composite optical bistable circuit is obtained.

(Operations and Effects of the Invention) In order to reduce the optical trigger level in a bistable semiconductor laser, the present invention employs a method in which an externally input trigger light is amplified by an optical amplifier and then applied to the bistable semiconductor laser. ing. Furthermore, since the application method is through an optical waveguide parallel to the striped active region of the bistable semiconductor laser and optically coupled, stable operation can be expected.

The present invention will be described in detail below with reference to the drawings.

(Embodiment) Fig. 1 is a configuration diagram showing the relative positional relationship between a bistable semiconductor laser and an optical amplifier according to an embodiment of the present invention, Fig. 2 is a perspective view thereof, and Fig. 3 a, b, c. represent cross-sectional views, respectively. Bistable semiconductor laser 1
has a striped active region consisting of first and second amplification sections 20 and 30 and an absorption region 10. The optical amplifier 2 includes an optical waveguide 110 parallel to and close to the active region of the bistable semiconductor laser 1, and an optical amplifier active region 100 connected thereto.
With this configuration, the bistable semiconductor laser 1 exhibits hysteresis in the current-optical output characteristics and the optical input-optical output characteristics. When input trigger light 200 is made incident from the input end 120 of the optical amplifier 2 with an appropriate bias current applied, it is amplified by the optical amplifier active region 100 and enters the optical waveguide 110. Optical waveguide 1
10 is optically coupled to the striped active region of the bistable semiconductor laser 1, so that the amplified input trigger light 200 is coupled to the bistable semiconductor laser 1 and turns the bistable semiconductor laser 1 into the "on" state. trigger on. The required level of this trigger light 200 can be extremely small since it is amplified by the optical amplifier 2.

This composite optical stabilizer circuit is manufactured as follows. First, on an n-type InP substrate 40, an n-
A double heterocrystal is fabricated by successively growing an InP buffer layer 41, a non-doped InGaAsP active layer 42, and a P-InP cladding layer 43. next,
A first pair of channels 50 and a second pair of channels 51 are formed by conventional photolithography and chemical etching. 1st channel vs. 50
distinguishes the striped active region of the bistable semiconductor laser 1 from the surrounding region, and the second channel pair 51 distinguishes the optical amplifier active region 100 and the optical waveguide 110 of the optical amplifier 2 from the surrounding region.

The channel width of each channel pair is approximately
7μm, and the width of the mesa between them is 1 to 1.5μm.
And so. The wafer in this state is placed in a liquid phase growth furnace, and a first current blocking layer 44 of P-InP and a first current blocking layer 44 of n-InP are formed.
A second current blocking layer 45, a P-InP buried layer 46, and a P-InGaAsP cap layer 47 are successively grown. At this time, by appropriately setting the supersaturation degree and growth time of the growing melt,
In the regions shown in FIGS. 3a and 3b, that is, in the first and second amplification sections 20 and 30 of the active region of the bistable semiconductor laser 1, and in the region of the optical amplifier active region 100 of the optical amplifier 2, The first and second current blocking layers 44 and 45 may not grow at all on top of the mesas formed by the first and second channel pairs 50 and 51. Also, the third
In the region shown in FIG. Since the mesa width is increased, the second current blocking layer 45 can be grown over both mesas.

An-Ge-Ni was applied to the entire surface of the wafer thus formed as the n-side electrode 60.
Cr-An as the third P-side electrodes 61, 62, 63
are formed by vapor deposition and heat treatment, respectively. Here, the first and second P-side electrodes 61 and 62 are divided in the resonator axis direction of the bistable semiconductor laser 1, and are connected to the first and second optical amplification sections 20 and 3, respectively.
It is formed at a position corresponding to the upper part of 0. On the other hand, the third P-side electrode 63 is formed at a position corresponding to the upper part of the active region 100 of the optical amplifier 2.

When 30 mA and 20 mA are applied to the first and second P-side electrodes 61 and 62 of this composite optical bistable circuit, respectively, and input trigger light 210 from one resonator end face 70 of the bistable semiconductor laser 1 is injected. ,
The light output 220 from the other resonator end face 71 was triggered to the "on" state when the input trigger light level was approximately 50 μW. In this state, the third P-side electrode 6
3, and when input trigger light 200 was injected from the input end 120, it was triggered to the "on" state at about 2.5 μW. That is, in the present invention, by integrating the optical amplifier 2, an optical bistable circuit with a low trigger level is realized.

In this embodiment, a striped active region of a bistable semiconductor laser 1 and an optical waveguide 110 of an optical amplifier 2 are used.
Due to the nature of crystal growth, areas where n-InP is formed close to each other are automatically covered with n-InP, making it a region where it is difficult for current to flow. That is, there is an advantage that the saturable absorption region of the bistable semiconductor laser 1 is automatically formed.

In the above embodiment, the bistable semiconductor laser employs a buried structure, so the striped active region has a laminated structure formed in stripes, but other structures, such as a planar stripe structure, have a laminated structure. Although it does not have a stripe structure, the optical bistable circuit of the present invention can also be obtained with a structure in which the region into which current is injected is striped, and this current injection region becomes a stripe-like active region. Further, this also applies to the optical amplifier 2.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an embodiment of the present invention, FIG. 2 is a perspective view thereof, and FIG. 3 is a sectional view thereof. In the figure, 1 is a bistable semiconductor laser, 2 is an optical amplifier, 10 is an absorption region, 20 and 30 are amplification sections,
40 is an InP substrate, 41 is a buffer layer, 42 is an active layer, 43 is a cladding layer, 44 and 45 are current blocking layers, 46 is a buried layer, 47 is a cap layer, 5
0,51 are channel pairs, 60 to 63 are electrodes, 1
00 represents an active region, and 110 represents an optical waveguide.

Claims (1)

[Claims] 1. A bistable semiconductor laser having a laminated structure including a striped active region, and an optical amplifier that guides trigger light to the bistable semiconductor laser, and the striped active region has an optical amplification section and an optical absorption region. and at least an electrode above the optical amplification section for injecting a current into the optical amplification section, the optical amplifier:
An optical bistable circuit comprising at least an optical waveguide arranged parallel to and optically coupled to the striped active region and an optical amplifier active region connected to the optical waveguide.