High power diffraction-limited ultrashort pulse generation from double tapered semiconductor laser diodes

Abstract

One promising way of generating high power diffraction-limited output from a semiconductor laser diode is to fabricate a double tapered device by varying the stripe width along the cavity, in order to produce wide stripes at the facets and a narrow stripe at the center. The narrow stripe near the middle of the cavity acts as a spatial filter to maintain a good quality spatially coherent output, whilst the wide stripes at the facets have the dual benefits of increasing the active volume (thus increasing optical power generation) and increasing the threshold power before catastrophic facet damage occurs. High power single lateral mode operation has already been demonstrated by using various tapered devices[l, 2, 3] and much work has been carried out on tapered semiconductor laser amplifiers [5, 4]. However, the nature of double tapered device in obtaining high power and diffraction limited output is still poorly understood and optimization in design is badly needed.