Compact InGaAsP/InP laser diodes with integratedmodeexpander for efficient coupling to flat-ended singlemode fibres

Abstract
Semiconductor lasers with short integrated mode expanders for efficient coupling to fiat-ended singlemode fibres are presented. Laser-to-fibre coupling efficiencies of –3 dB, an improvement of 7 dB compared with conventional laser diodes, have been achieved. Simultaneously, the lateral alignment tolerances, for a 1 dB reduction of the coupling efficiency have been relaxed to ±1.8 µm.