VERTICAL CAVITY SURFACE EMITTING LASER

Abstract

A vertical cavity surface emitting laser includes a cavity formed by a pair of reflectors on a substrate and an active region interposed in the cavity. In the vertical cavity surface emitting laser, at least one of the reflectors that form the cavity has a refractive index periodic structure produced by arranging a first medium and a second medium so as to make the refractive index change periodically in in-plane directions of the substrate and the cross sectional area of the first medium in the in-plane directions changes in the direction of the thickness of the first medium. The vertical cavity surface emitting laser has reflectors having a wide reflection band.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic perspective view of a two-dimensional photonic crystal illustrating an embodiment of the present invention.

FIG. 2 is a schematic perspective view of a two-dimensional photonic crystal also illustrating an embodiment of the present invention.

FIG. 3 is a graph illustrating a photonic band structure also illustrating an embodiment of the present invention.

FIG. 4 is a schematic cross sectional view of a cavity reflector, illustrating a configuration thereof that can be used for an embodiment of the present invention.

FIG. 5 is a schematic cross sectional view of a cavity reflector, illustrating another configuration thereof that can be used for an embodiment of the present invention.

FIG. 6 is a graph illustrating the photonic band of each of the two-dimensional photonic crystals having different hole diameters (a graph of the photonic band of TM polarization) in an embodiment of the present invention.

FIGS. 7A and 7B are graphs illustrating the reflection characteristics of the two-dimensional photonic crystal reflector of an embodiment of the present invention. FIG. 7A is a graph illustrating the reflection characteristic of the two-dimensional photonic crystal reflector obtained relative to a single band, and FIG. 7B is a graph illustrating the reflection characteristic of the two-dimensional photonic crystal reflector obtained relative to four bands.

FIGS. 8A and 8B are schematic views of the vertical cavity surface emitting laser of Example 1 of the invention, illustrating the configuration thereof. FIG. 8A is a schematic cross sectional view taken along a direction perpendicular to the substrate of the vertical cavity surface emitting laser of Example 1, and FIG. 8B is a schematic plan view as viewed in the direction perpendicular to the surface of the cavity reflector of Example 1.

FIG. 9 is a schematic illustration of the two reflectors that form the cavity of Example 1 of the invention, illustrating the relative positional relationship thereof.

FIG. 10 is a schematic cross sectional view of the vertical cavity surface emitting laser of Example 2 of the invention taken along a direction perpendicular to the substrate.

FIGS. 11A and 11B are schematic views of the photonic crystal reflector of Example 2 of the invention. FIG. 11A is a schematic cross sectional view taken along a direction perpendicular to the photonic crystal surface, and FIG. 11B is a schematic plan view as viewed in the direction perpendicular to the photonic crystal surface.

FIGS. 12A and 12B are schematic views of the photonic crystal reflector of Example 3 of the invention. FIG. 12A is a schematic cross sectional view taken along a direction perpendicular to the photonic crystal surface, and FIG. 12B is a schematic plan view as viewed in the direction perpendicular to the photonic crystal surface.

FIGS. 13A and 13B are schematic views of the photonic crystal reflector of Example 4 of the invention. FIG. 13A is a schematic cross sectional view taken along a direction perpendicular to the photonic crystal surface, and FIG. 13B is a schematic plan view as viewed in the direction perpendicular to the photonic crystal surface.

FIG. 14 is a schematic cross sectional view taken along a direction perpendicular to the substrate of the vertical cavity surface emitting laser of Example 5 of the invention.

Claims

1. A vertical cavity surface emitting laser comprising a cavity formed by a pair of reflectors on a substrate and an active region interposed in the cavity; at least one of the reflectors forming the cavity having a refractive index periodic structure produced by arranging a first medium and a second medium so as to make the refractive index change periodically in in-plane directions of the substrate;the cross sectional area of the first medium in the in-plane directions changing in the direction of the thickness of the first medium.

2. The vertical cavity surface emitting laser according to claim 1, wherein the cross sectional area of the first medium changes continuously or quasi-continuously in the direction of the thickness of the first medium.

3. The vertical cavity surface emitting laser according to claim 2, wherein one of the mediums that form the refractive index periodic structure is holes.

4. The vertical cavity surface emitting laser according to claim 3 formed by laying refractive index periodic structures having holes and the hole diameter of the holes of each of the layers changes continuously or quasi-continuously in the direction perpendicular to the surfaces of the reflectors.

5. The vertical cavity surface emitting laser according to claim 2, wherein one of the mediums that form the refractive index periodic structure is a multilayer film made of films having mutually different compositions; andthe refractive index of each of the layers of the multilayer film changes continuously or quasi-continuously in the direction perpendicular to the surfaces of the reflectors.

6. A vertical cavity surface emitting laser comprising a multilayer film reflector, a first clad layer, an active layer, a second clad layer and a reflector in this order on a substrate; the reflector having a structure produced by arranging a first medium and a second medium so as to make the refractive index change periodically in in-plane directions of the substrate;the cross sectional area of the first medium in the in-plane directions gradually diminishing as the distance to the second clad layer is smaller.