Control of polarisation of vertical cavity surface emitting lasers

摘要

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.