POLARISATION INSENSITIVE SEMICONDUCTOR OPTICAL AMPLIFIER WITH BURIED LATERALY TAPERED ACTIVE WAVEGUIDE

Abstract

Semiconductor optical amplifiers are expected to find a variety of applications in optical telecommunication systems, on the one hand, for their regeneration capabilities and, on the other hand, owing to their short carrier lifetime in contrast to fiber amplifier, as fast optical switch or in line detector. Low polarisation sensitivity, low facet reflectivities and low insertion losses are key points for system applications. Thus far, investigations have been mainly focused on polarisation sensitivity and facet reflectivity. Considering only bulk material and buried structures, polarisation sensitivity less than 1 dB have been reported with amplifier structures based on nearly square and sub-micron active stripe section [1,2]. Such tiny dimensions are imposed by the fact that, in buried structures, the lateral guiding is a strong index one. So, as the index difference between active material and InP substrate is very high, the active stripe width has to be less than two times the tickness in order to reach a polarisation sensitivity less than 2 dB [3].