THE EXPANDED MODE LASER - A ROUTE TO LOW COAST OPTOELECTRONICS

At present, the widespread use of optoelectronic components is restric ted by their high cost. Up to 90% of the cost of a semiconductor laser is in the packaging, with the fibre-chip alignment the major part. In this paper, an approach to low cost packaging is described, which use s an integrated mode size transformer to match the laser output to the fibre mode. This improves the alignment tolerance of the laser-fibre coupling by more than a factor of three, allowing simple passive align ment approaches to be used. It requires only minor modification to the processing of a standard buried heterostructure laser, and allows the coupling efficiency to be optimised without compromising the performa nce of the laser. The design of a silicon submount for passive laser-f ibre alignment is described and coupling losses as low as 1.2 dB to st andard cleaved single mode fibre are reported. The technology that has been developed is generic and its successful application to other opt oelectronic devices such as fibre grating lasers, semiconductor optica l amplifiers and laser arrays is described.