Slow and fast light in quantum dot based semiconductor optical amplifiers

: Recent progress in the field of quantum dot/dash based semiconductor optical amplifiers (SOAs) for slow and fast light is presented. Room temperature fast light has been obtained in InAs/InP QDash based SOA by means of coherent population oscillation and four wave mixing (FWM) effects. Typical optical delays amount to 55 ps at 2 GHz. Growth optimization of the QDashes allowed to achieve high modal gain, leading to very similar performances, e.g. gain and FWM efficiency, to those of a bulk SOA. A new method based on linear spectrograms is also introduced to measure the phase shift induced by wave mixing in a SOA. 1. Introduction: group velocity control in semiconductor optical amplifiers. Controllable optical delays based on group index modification have recently received much attention [Chuang1]. Indeed, slow and fast light are attractive for many applications such as optical buffers for telecommunication [Chuang1], control of optically carried microwave signals for phased array antennas [Mork1], tuneable notch filter for broad band access network [Mork2] and optoelectronic processing functions for defense applications [Mork3, Berger]. Slow light schemes are based on the modification of the waveguide and/or material dispersion [Chuang1]. The former method can be performed using periodic structures like two dimension photonic crystals or Fabry-Perot resonators. Material dispersion can be changed using various methods such as the electromagnetic induced transparency, non linear effects in optical fibers like stimulated Brillouin scattering, or by changing the gain or the absorption spectrum of semiconductor devices via wave mixing [Chuang1].