Strongly index-guided II-VI laser diodes

Ridge-waveguide laser diodes based on Be-chalcogenides have been fabricated by reactive ion etching and planarization with polyimide. Etching close to or even through the active layer is demonstrated to suppress the current s preading efficiently, resulting in a signficant reduction of the threshold current as compared to gain-guided structures. This allows the fabrication of narrow, strongly index-guided II-VI laser diodes with a ratio between th e vertical and the lateral far-field angle of, e.g., 1.2:1 for L-x = 1 mu m .