Observation of Cross Phase Modulation in a Semiconductor Laser Amplifier near 1.3 um

Abstract

Self phase modulation in optical amplifiers has been theoretically and experimentally studied [1]. The self phase modulation is due to the dynamic change in the carrier density resulting from gain saturation that occurs in the amplifier. It is possible to obtain phase modulation of another beam (signal beam) that differs in frequency or in polarization with respect to the beam that experiences gain saturation (pump beam). This situation is referred to as cross phase modulation in an amplifying medium; that is to say, the intensity of a strong pulse affects the phase of a weaker pulse. Cross phase modulation due to the Kerr effect in nonlinear media such as glass and liquids has been reported [2] and was referred to as induced phase modulation. In this paper we report the observation of cross phase modulation in a semiconductor laser amplifier. It was the intent of the authors to begin research on a potentially integrable tunable chirping element on a tens of picosecond time scale. Other attempts at making a tunable chirping element could be realized using electrooptic phase modulators.