SEMICONDUCTOR LASER DEVICE WITH SMALL VARIATION OF THE OSCILLATION WAVELENGTH

Abstract

A semiconductor laser has a structure in which the following layers are stacked on one another over an n-type substrate: a buffer layer, a diffraction grating layer, a diffraction grating burying layer, a light confining layer, a multiple quantum well active layer, a light confining layer, and a cladding layer. In this structure, the distance D between the center of the active layer and the interface between the n-type substrate and the buffer layer is set to a value longer than the 1/e2-beam spot radius a of the laser light.

Description

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 shows a cross-sectional view of a semiconductor laser;

FIG. 2 shows a cross-sectional view of a semiconductor laser of a ridge type structure;

FIG. 3 shows a cross-sectional view of a semiconductor laser of a buried hetero type structure; and

FIGS. 4 and 5 show the relationship between the thickness of the buffer layers and a beam spot radius of the laser light.

Claims

1. A semiconductor laser device comprising: an n-type semiconductor substrate;a buffer layer on said semiconductor substrate and containing an n-type impurity;a diffraction grating layer on said buffer layer; andan active layer on said diffraction grating layer and generating laser light, wherein distance D between the center of said active layer and the interface between said semiconductor substrate and said buffer layer is longer than 1/e2-beam spot radius a of the laser light.

2. The semiconductor laser device according to claim 1, wherein the concentration of said n-type impurity contained in said buffer layer varies about a mean value within ±10% depending on location of said n-type impurity within said buffer layer.

3. The semiconductor laser device according to claim 1, wherein the distance D is smaller than √2*a.

4. The semiconductor laser device according to claim 1, wherein: said semiconductor substrate is n-type InP; andsaid semiconductor laser device has a ridge structure.

5. The semiconductor laser device according to claim 1, wherein: said semiconductor substrate is n-type InP; andsaid semiconductor laser device has a buried heterostructure.

6. The semiconductor laser device according to claim 1, wherein said buffer layer is formed using one of metal organic chemical vapor deposition, molecular beam epitaxy, and liquid phase epitaxy.

7. The semiconductor laser device according to claim 1, including a diffraction grating burying layer containing an n-type impurity located between said diffraction grating layer and said active layer, wherein said n-type impurities in said diffraction grating burying layer and in said buffer layer are the same element.

8. The semiconductor laser device according to claim 7, wherein said n-type impurities are one of Si and S.

9. The semiconductor laser device according to claim 1, wherein: said semiconductor substrate contains an n-type impurity; andsaid n-type impurities contained in said semiconductor substrate and in said buffer layer are the same element.

10. The semiconductor laser device according to claim 9, wherein said n-type impurities are selected from the group consisting of Si, S, and Se.