Polarisation control in VCSELs by elliptic surface etching

Abstract

850 nm-wavelength vertical-cavity surface-emitting lasers (VCSELs) with an elliptical shallow surface relief having various aspect ratios and orientations have been fabricated. Using appropriate etch dimensions, VCSELs of up to 12.5 µm active diameter are forced to operate on the fundamental mode for a certain current range. By aligning the longer axis of the etched ellipse with the [011] or [011] crystal axis, the polarisation of the fundamental mode is pinned accordingly with a polarisation suppression ratio of ∼30 dB.