JPH04149512A - Integrated semiconductor optical amplifier - Google Patents

Abstract

PURPOSE:To keep amplification degree obtained for the amount of injected carrier high by intentionally causing side etching only in an optical amplification layer and burying a side etched part by utilizing a mass transport phenomenon. CONSTITUTION:An InGaAsP optical waveguide layer 5, an InP barrier layer 4, an InGaAsP optical amplification layer 3, an InP clad layer 2, and an InGaAsP cap layer 1 are multilayered and grow on an InP substrate 6, then a protective film is attached only to a part which is used as the optical amplifier thereafter and the upper four layers being the rest are removed. Next, the clad layer 2 and the InGaAsP1 are allowed to grow again on a part except the optical amplifier part to which the protective film is attached. Thereafter, the optical amplifier and the optical waveguide are formed with the ordinary technique of lithography and etching. Furthermore, in order to bury both side surfaces of the optical amplifier 3, selective etching is performed to the optical amplifier 3 and the etched part is buried by the mass transport. The buried part is an InP buried layer 7.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an optical amplifier suitable for integration with an optical switch or an optical waveguide in an integrated optical device.

[Conventional technology]

Conventionally, the structure of an integrated optical amplifier has been disclosed in Japanese Patent Application No. 1-1.
7604.

[Problem to be solved by the invention]

The above conventional technology uses a ridge-type optical waveguide to confine light in a direction perpendicular to the direction of propagation of the light within the optical waveguide. No consideration was given to the exposed layer, and the injected carriers (
electrons and holes) are lost to non-emission due to surface states,
There has been a problem in that the proportion contributing to light amplification decreases. The present invention reduces the proportion of carriers injected into the exposed optical amplification layer that are lost to non-emission, and improves the optical amplifier. To improve the efficiency of injection, that is, with respect to the amount of injected carriers,
The object of the present invention is to provide a wedge-type optical amplifier that can obtain a large amplification degree and is suitable for integration with an optical waveguide or a carrier injection type optical switch.

[Means to solve the problem]

In order to achieve the above objective, we consciously caused side etching using etching that selectively acts only on the optical amplification layer, without changing the basic structure of the optical amplifier, which is suitable for integration with optical waveguides. In addition, a site-etched portion is embedded by utilizing the mass transport phenomenon.

The mass transport phenomenon is a phenomenon in which when the InP cover is heated together with the substrate, acute angle portions are rounded due to the movement of atoms on the crystal surface, and extremely small portions such as the site-etched portions of the light amplification layer are buried with InP.

[Effect]

Since both sides of the optical amplification layer are filled with semiconductor material, there are no exposed optical amplification layer parts, so there are no carriers lost in non-emission processes related to surface states, and the efficiency of the optical amplifier is improved. Since the semiconductor material used for embedding has a larger energy bandgap than the optical amplification layer, the injected carriers flow into the optical amplification layer, which has a small energy bandgap, and are No problems occur.

If the purpose is simply to prevent exposure of the ridge sides, the same result can be obtained by buried growth on the ridge sides, but the refractive index of air is 1.
When using a semiconductor material with a refractive index of approximately 3,
The confinement conditions of the optical waveguide will change. Even if a fully buried optical waveguide is redesigned to compensate for this drawback, the difference in refractive index between the leading wave layer and the cladding layer cannot be made large, resulting in weak confinement of light, resulting in a carrier-injection type optical waveguide. The optical switch section no longer operates effectively.

That is, it is inevitable that a carrier injection type optical switch and an optical amplifier that can be integrated into an optical waveguide have a ridge-type structure.

〔Example〕

An embodiment of the present invention will be described below with reference to FIG.

FIG. 1(a) shows a cross-sectional structure of an integrated optical amplifier. In this example, an InGaAsP optical waveguide layer 5 (absorption edge wavelength λg=
1.15 μm), In, P barrier layer 4, InGaAsP optical amplification layer 3 (absorption edge wavelength λg = 1, 3 μm)
InP cladding layer 2, InGaAsP capping layer 1. is grown in multiple layers, and only the part that will be used as an optical amplifier later has 8
102 protective film and the remaining upper four layers, namely In
GaAsP cap layer 1, InP cladding layer 2, InG
The aAsP optical amplification layer 3 and the InP barrier layer 4 were removed by selective etching.

Next, I
The nP crat layer 2, InGaAsP1, was regrown.

Thereafter, an optical amplifier and an optical waveguide having the shapes shown in FIGS. 1(a) and 1(b) were formed by ordinary lithography and etching techniques.

Furthermore, as shown in FIG. 1, in order to bury both side surfaces of the InGaAsP optical amplification layer 3, selective etching was performed which selectively acts only on the +InGaAsP optical amplification layer 3 to form intentional side etched portions. This side etched portion is filled in by mass transport. This embedded part is I
It is nP embedded M7. This part differs from the slave side in FIG. 2.

The optical amplifier in FIG. 1(a) and the optical waveguide in FIG. 1(b) are connected by a common optical waveguide layer 3 formed in the first crystal growth, and are connected because they have a common ridge structure. We were able to suppress the loss to less than 1dB. Furthermore, fewer carriers flow through non-emission processes due to surface states, making it possible to reduce the injection current needed to obtain the same gain compared to the conventional example.

〔Effect of the invention〕

According to the present invention, the efficiency of the optical amplifier can be increased because the amount of carriers contributing to non-radiative recombination can be reduced by surface states. In addition, since internal progress of crystal defects caused by current leakage paths flowing through surface states is eliminated, reliability for long-term use can be improved. Furthermore, since a structure having a common ridge structure and a common optical waveguide layer can be created, it is possible to easily integrate an optical waveguide and an optical amplifier with less connection loss.

[Brief explanation of the drawing]

FIG. 1(a) is a cross-sectional view of a ridge-type optical amplifier which is an embodiment of the present invention, FIG. 1(b) is a cross-sectional view of an optical waveguide that can be integrated and integrated with the optical amplifier shown in FIG. The figure is a sectional view of a conventional optical element. 1 = 4nGaAsP cap layer, 2 ・InP cladding layer, 3 ・=InGaAsP optical amplification layer, 4 ・=
InP barrier layer, 5...InGaAsP optical waveguide layer,
6-InP substrate, 7-InP Figure 1 (α) (b)

Claims (1)

[Claims] 1. In a traveling wave semiconductor optical amplifier having a ridge structure, only the optical amplification layer exposed on the side surface of the ridge is selectively side-switched, and a semiconductor material having a larger forbidden band width than the optical amplification layer is used as a side switch. An integrated semiconductor optical amplifier characterized in that only the etched portion is buried. 2. An integrated semiconductor device characterized in that the optical amplifier according to claim 1 is completely monolithically integrated with an optical waveguide and a carrier injection type optical switch.