JPH05343807A - Surface-type optical functional element - Google Patents

Abstract

PURPOSE:To realize a surface-type optically bistable laser, whose oscillation threshold is low, as a surface-type optical functional element. CONSTITUTION:The followings are formed on an n-type GaAs substrate 10: an n-type GaAs/AlAs multilayer reflection film 20; an n-type GaAs layer 11 ; an In0.2Ga0.8As quantum well layer 12 as an undoped active layer; a p-type GaAs clad layer 13; and a p-type GaAs/AlAs multilayer reflection film 21. The p-type GaAs/AlAs multilayer reflection film 21 is etched partly; after that, the n-type GaAs layer 11, the undoped active layer 12, the p-type GaAs clad layer 13 and the p-type GaAs/AlAs multilayer reflection film 21 are etched partly. An insulating film 22 is formed selectively; after that, an anode electrode 31 is former on the p-type GaAs clad layer 12, and a cathode electrode 30 is formed on the n-type GaAs/AlAs multilayer reflection film 20. A region into which an electric current is not injected out of the active layer 12 functions as a supersaturation absorption region, and the optical bistability of the title element can be realized.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a planar optical functional device for optical transmission and optical information processing.

[0002]

2. Description of the Related Art Research on a semiconductor laser, which is a light source for optical transmission and optical information processing, is under way. Among them, the surface-type semiconductor laser is capable of (1) forming a monolithic resonator,
(2) It is possible to inspect each wafer before element isolation, (3)
Dynamic single wavelength operation is possible, (4) Large emission area, irregular emission circular beam is possible, (5) High density two-dimensional laser array is possible, (6) Integration of three-dimensional array device by stacking, etc. There are advantages. A pioneering research was conducted by Iga et al. On surface-type semiconductor lasers, and the results of their series of researches are based on the journal of Quantum Electronics (Tournfl oo) by Iga et al., Published in 1988.
f Quantum Electronics) 24th
It is summarized in the paper on page 1845, including its historical background.

Further, the surface-type optical functional element is an element which performs optical information processing by making use of the advantages of the surface-type semiconductor laser described above.
It is expected to enable two-dimensional parallel optical information processing aiming at large-capacity information processing. As one of such surface-type optical functional elements, there is a surface-type optical bistable laser having a structure shown in FIG. This surface-type optical bistable laser is disclosed in Nitta et al., Published in 1988, IEICE Transactions (C), Volume J71-C, page 1267, and has a thickness of 1 μm on an n-type GaAs substrate. n-type Al _0.5 Ga _0.7 As etching stop layer, 0.5 μm thick n-type GaAs supersaturated absorption layer, 3 μm
m-thick n-type Al _0.3 Ga _0.7 As clad layer, 3 μm-thick p-type GaAs active layer 1 μm-thick p-type Al _0.3 Ga _0.7
As clad layer, 0.2 μm thick p-type Al _0.1 Ga _0.9
This is a structure in which As window cap layers are laminated.

[0004]

However, the conventional surface-type optical functional device has the following problems. One of the surface-type optical functional elements is a surface-type optical bistable laser.
In the conventional device, as shown in FIG. 7, the active layer and the saturable absorption layer are arranged in series in the light traveling direction, so that there is a problem that the oscillation threshold is as large as 430 mA due to the absorption of the saturable absorption layer.

An object of the present invention is to realize a surface type optical bistable laser having a low oscillation threshold as a surface type optical functional element.

[0006]

A surface-type optical functional device of the present invention has a first conductive type semiconductor multilayer reflective film on a first conductive type semiconductor substrate, and a first conductive type semiconductor multilayer reflection film thereon. Spacer layer, an undoped active layer having a light oscillating function, and a second conductive type clad layer on the active layer, and a second conductive type semiconductor multilayer reflective film on the clad layer. Alternatively, an electrode having a dielectric multilayer reflection film or a metal reflection film, which is in contact with the second conductive type semiconductor layer, is formed on at least the cladding layer, and the supersaturation absorption layer is in the same plane as the active layer, In addition, the active layer is formed in a portion where the emitted light is exuding.

Alternatively, the surface-type optical functional element of the present invention has a first conductive type semiconductor multilayer reflective film on a first conductive type semiconductor substrate, and a second conductive type semiconductor layer thereon. An undoped active layer having a light oscillating function on the second conductive type semiconductor layer, and a first conductive type semiconductor layer and a second conductive type cladding layer on the active layer, A second conductive type semiconductor multilayer reflective film, a dielectric multilayer reflective film or a metal reflective film is formed on the clad layer, and an electrode contacting the second conductive type semiconductor layer is formed on at least the clad layer. Has been
The supersaturated absorption layer is formed in the same plane as the active layer and in a portion where the light emitted from the active layer exudes.

Alternatively, the surface-type optical functional element of the present invention is characterized in that the supersaturation absorption layer is a high resistance layer in the above-mentioned configuration, or the surface-type optical functional element of the present invention is In the above structure, the refractive index of the supersaturated absorption layer is lower than the refractive index of the active layer.

[0009]

[Operation] The operation will be described. First, the operation of the surface-type optical functional element having the first configuration will be described. In order to achieve optical bistability, most semiconductor lasers have a saturable absorption layer and an active layer arranged in series in the cavity direction. However, when the supersaturated absorption layer and the active layer are arranged in series in the light traveling direction, the oscillation threshold value is greatly affected by the absorption loss of the supersaturated absorption layer and becomes large. On the other hand, in the present invention, the supersaturated absorption layer and the active layer are arranged in parallel with respect to the traveling direction of light, and are formed in the portion where the light emitted from the active layer exudes. This makes it possible to adjust the light trapped in the saturable absorption layer and reduce the influence of absorption of the saturable absorption layer. That is, the oscillation threshold can be reduced.

In the surface type optical functional device having the second structure, the same principle as that of the first structure is applied to the pnpn structure (current-voltage and voltage-optical characteristics are bistable) to obtain current-optical output characteristics. Also has bistability. Thereby, optical information processing with a high degree of freedom can be realized.

The surface-type optical functional element of the third structure is characterized in that the supersaturation absorption layer is a high resistance layer, which makes it possible to efficiently inject current into only the light emitting portion. As a result, it becomes possible to realize a surface-type optical functional device having an oscillation threshold smaller than that of the first configuration.

The surface-type optical functional element having the fourth structure is characterized in that the refractive index of the saturable absorbing layer is lower than that of the active layer. This refractive index distribution controls the confinement of light in the active layer and controls the influence of the absorption loss of the supersaturated absorption layer on the oscillation threshold.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS This embodiment will be described in detail with reference to the drawings. FIG. 1 is a diagram showing the structure of a surface-type optical functional element according to the first embodiment of the present invention. FIG. 2 is a diagram showing the structure of the surface-type optical functional element of the second embodiment of the present invention. FIG. 3 is a diagram showing the structure of the surface-type optical functional element of the third embodiment of the present invention. FIG. 4 is a diagram showing the structure of the surface-type optical functional device of the fourth embodiment of the present invention. FIG. 5 is a view showing the structure of the surface-type optical functional device of the fifth embodiment of the present invention. FIG. 6 is a diagram showing the structure of a surface-type optical functional element according to the sixth embodiment of the present invention.

The structure of this embodiment will be described below according to the manufacturing procedure. First, the structure of the first embodiment will be described with reference to FIG. An n-type GaAs / AlAs multilayer reflection film 20 and an n-type GaA are formed on the n-type GaAs substrate 10 by molecular beam epitaxy (hereinafter abbreviated as MBE).
s layer 11, In _0.2 Ga _0.8 A as undoped active layer
s quantum well layer 12, p-type GaAs cladding layer 13 (thickness 0.5 μm), p-type GaAs / AlAs multilayer reflective film 21
To grow sequentially.

A part of the p-type GaAs / AlAs multilayer film 21 is etched, and then the n-type GaAs layer 11, three In _0.2 Ga _0.8 As quantum well layers (thickness 8 mn) 12 as an undoped active layer, p-type GaAs. Clad layer 1
3. Part of the p-type GaAs / AlAs multilayer reflective film 21 is etched. After the silicon nitride film 22 is selectively formed as an insulating film, the p-type GaAs cladding layer 12 and the p-type G are formed.
An anode electrode 31 is formed so as to cover the aAs / AlAs multilayer reflective film 21. The anode electrode 31 on the p-type GaAs / AlAs multilayer reflective film 21 functions as a metal reflective film. Further, the cathode electrode 30 is formed on the n-type GaAs / AlAs multilayer reflective film 20.

A region 40 of the active layer 12 to which no current is injected functions as a supersaturation absorption region 40, and optical bistability can be realized. The oscillation threshold current is 10 mA or less, and it can be seen that the oscillation threshold current can be greatly reduced compared to the conventional example of 430 mA.

FIG. 2 is a diagram showing the structure of a planar optical functional device according to the second embodiment of the present invention.

The difference from the first embodiment shown in FIG. 1 is that the growth layer sandwiched by the multi-layered reflection film has an n-type semiconductor layer 11, a p-type semiconductor layer 15, an undoped active layer 12, and an n-type semiconductor layer. 1
4 has a pnpn structure composed of the p-type semiconductor layer 13. Other than this, it is the same as the embodiment of FIG. By adopting such a structure, it is possible to realize an element having the function while utilizing the characteristics of the first embodiment. This device combines the advantages of light and the advantages of electricity to realize light emission, light reception, threshold value, and memory operation. Further, similarly to the first embodiment, the region 40 of the active layer 12 into which no current is injected functions as a supersaturation absorption region, and optical bistability can be realized. The oscillation threshold current is 10 mA or less as in the first embodiment, and it can be seen that the oscillation threshold current can be greatly reduced as compared with the conventional example of 430 mA.

FIG. 3 is a diagram showing the structure of a planar optical functional device according to a third embodiment of the present invention. Here, the high resistance layer 50 is formed by proton injection, and the supersaturated absorption layer 4 of FIG.
0 has a high resistance. Other than this, it is the same as the embodiment of FIG. As a result, the current can be efficiently confined only in the light emitting portion, and the oscillation threshold value can be reduced to 5 mA or less.

FIG. 4 is a diagram showing the structure of a planar optical functional device according to a fourth embodiment of the present invention. Here, the supersaturated absorption layer 40 of FIG. 2 is made into the high resistance layer 50 by proton injection. As a result, similarly to the third embodiment, the current can be efficiently confined only in the light emitting portion, and the oscillation threshold is 5
It could be reduced to mA or less.

FIG. 5 is a diagram showing the structure of a planar optical functional device according to a fifth embodiment of the present invention. Here, Zn is diffused into the supersaturated absorption layer 40 of FIG.
The layer 60 has a refractive index of 0 lower than that of the active layer 12 and has a high resistance due to proton injection. As a result, the current can be efficiently confined only in the light emitting portion, and the oscillation threshold value can be reduced to 2 mA.

FIG. 6 is a diagram showing the structure of a planar optical functional device according to a sixth embodiment of the present invention. Here, too, the saturable absorber layer 4 is diffused by Zn diffusion into the saturable absorber layer 40 of FIG.
The layer 60 has a refractive index of 0 lower than that of the active layer 12 and has a high resistance due to proton injection. As a result, the current can be efficiently confined only in the light emitting portion, and the oscillation threshold value is 2 m as in the fifth embodiment.
It could be reduced to A or less.

The semiconductor material is not limited to the GaAs-based material described above, and may be an InP-based material, for example. Further, the multilayer reflective film is not limited to the semiconductor, but may be any other material such as a dielectric as long as the material can even increase the reflectance.

[0024]

As described above, a surface-type optical bistable laser having a low oscillation threshold (10 mA or less) can be realized as a surface-type optical functional element.

[Brief description of drawings]

FIG. 1 is a diagram showing a structure of a surface-type optical functional device according to a first embodiment of the present invention.

FIG. 2 is a diagram showing a structure of a surface-type optical functional device according to a second embodiment of the present invention.

FIG. 3 is a diagram showing a structure of a surface-type optical functional device according to a third embodiment of the present invention.

FIG. 4 is a diagram showing a structure of a surface-type optical functional device according to a fourth embodiment of the present invention.

FIG. 5 is a diagram showing a structure of a surface-type optical function element of a fifth embodiment of the present invention.

FIG. 6 is a diagram showing a structure of a surface-type optical functional device according to a sixth embodiment of the present invention.

FIG. 7 is a diagram showing a structure of a conventional planar optical function element.

[Explanation of symbols]

 10 semiconductor substrate 11 n-semiconductor layer 12 undoped active layer 13 p-semiconductor layer 14 n-semiconductor layer 15 p-semiconductor layer 20 n-semiconductor multilayer film 21 p-semiconductor multilayer film 22 insulating film 30 electrode 31 electrode 40 supersaturation absorption Region 50 High resistance layer 60 Low refractive index layer

Claims (4)

[Claims] 1. A first conductive type semiconductor multilayer reflective film on a first conductive type semiconductor substrate, a first conductive type spacer layer, and an undoped active layer having a light oscillating function. And a second conductive type clad layer on the active layer, and a second conductive type semiconductor multilayer reflective film, dielectric multilayer reflective film or metal reflective film on the clad layer, An electrode in contact with the second conduction type semiconductor layer is formed on at least the cladding layer, and a non-current injection region of the active layer, which functions as a saturable absorption layer, seeps out light emitted from the active layer. A surface-type optical functional element characterized by being formed in a part. 2. A first conductive type semiconductor multilayer reflection film on a first conductive type semiconductor substrate, and a second conductive type semiconductor layer on the first conductive type semiconductor multilayer reflection film, and the second conductive type semiconductor layer. An undoped active layer having an optical oscillation function, a first conductive type semiconductor layer and a second conductive type clad layer on the active layer, and a second conductive type on the clad layer. Type semiconductor multi-layer reflection film, dielectric multi-layer reflection film or metal reflection film, and an electrode in contact with the second conductive type semiconductor layer is formed on at least the cladding layer to absorb supersaturation in the active layer. A planar optical functional element, wherein a non-current injection region serving as a layer is formed in a portion where the light emitted from the active layer is exuding. 3. The surface-type optical functional element according to claim 1, wherein the supersaturation absorption layer is a high resistance layer. 4. The surface-type optical functional element according to claim 1, 2, or 3, wherein the refractive index of the saturable absorption layer is lower than the refractive index of the active layer. Optical functional element.