Fast absorption recovery and wavelength conversion in 1.5mm AlInGaAs MQW lasers

In recent years there has been a high level of interest in the properties of fast semiconductor saturable absorbers operating at λ ∼ 1.5»m. The applications for these include the fabrication of passively modelocked lasers[1] and wavelength conversion of optical data streams through cross-absorption modulation. To enable these effects to be utilised at the highest repetition rates, very fast absorption recovery times are required, in materials that can be conveniently integrated with optical gain elements. Several methods for achieving very short absorption recovery times have been demonstrated such as the inclusion of high densities of crystal defects in the material and the use of intersubband transitions. However, it is not possible to integrate these with gain elements operating at the same wavelength without the use of expensive and technologically demanding epitaxial regrowth processes.