US 6,785,320 B1 · Control of polarisation of vertical cavity surface emitting lasers

Abstract

A vertical cavity surface emitting laser (VCSEL) comprising a one dimensional grating structure configured to act as a waveguide, preferably located at an end surface of the VCSEL, for selectively reflecting more of a first polarisation of light back into the cavity of the VCSEL than a second orthogonal polarisation of light. Preferably the VCSEL comprises an upper Bragg mirror, a gain region, and a lower Bragg mirror, and the one dimensional grating structure is located on a top layer of the upper Bragg mirror and the top layer of the upper Bragg mirror has a thickness such that the reflected light of one polarisation constructively interferes with light of said one polarisation which is reflected by the upper Bragg mirror. The VCSEL will then lase at the polarisation which is more predominantly reflected by the grating structure.

Claims28

Dependent claims

A vertical cavity surface emitting laser (VCSEL), said VCSEL comprising:

a cavity;
and
a one dimensional grating layer, wherein the layer is a first order one dimensional diffraction grating, said layer comprising a waveguide extending in a direction perpendicular to an axis of the VCSEL, said grating having a pitch such that a portion of the light from the cavity incident normal to the grating grooves is directly reflected back into the cavity and a portion of the light from the cavity incident normal to the grating grooves is indirectly reflected back into the cavity by being diffracted into the waveguide and subsequently diffracted back out of the waveguide and into the cavity, wherein light having a first polarisation is selectively promoted within the cavity as compared to light having a second orthogonal polarisation by the one dimensional grating layer, said grating layer arranged such that for the second polarisation of light the indirectly reflected light interferes destructively with the directly reflected light.

A method of controlling the polarisation of light emitted by a vertical cavity surface emitting laser (VCSEL) comprising the steps of:

using a one dimensional grating layer for preferentially promoting gain of a first polarisation of light as compared to gain of a second polarisation of light within the VCSEL, said layer is a first order one dimensional diffraction grating which is formed as a layer of the VCSEL;
configuring said layer to act as a waveguide in a direction perpendicular to the axis of the VCSEL;
and
configuring the grating to have a pitch chosen so that part of the light from the VCSEL cavity incident normal to the grating grooves is reflected directly back into the VCSEL cavity and part of the light from the VCSEL cavity incident normal to the grating grooves is indirectly reflected back into the VCSEL by being diffracted into the waveguide and subsequently diffracted back out of the waveguide and into the VCSEL cavity, wherein the reflected light interferes destructively with the directly reflected light.

1 more element

Dependencies are inferred from the claim text.

Control of polarisation of vertical cavity surface emitting lasers

Life of this patent

Control of polarisation of vertical cavity surface emitting lasers

Life of this patent

Abstract

Claims28