Spatial Mode Discrimination in a Vertical Cavity Surface Emitting Laser by a Fabry-Perot Etalon

Abstract

Methods to increase the cw power of VCSELs generally require increases in mode area. To maintain single mode operation, a strong mechanism to discriminate against higher-order modes must be incorporated in the optical resonator structure. Spatial filtering methods have been employed in the far field to selectively enhance the modal reflectivity of the fundamental VCSEL mode [1]. However, for large aperture VCSELs, the far field light distribution is usually produced by a lens, making integration of the lens and filter difficult. In this experiment, we use the angular reflectivity properties of a Fabry-Perot to perform spatial filtering in the near field [2], permitting a modal selection mechanism that can be easily integrated into the VCSEL structure.