Small-Signal Cross-Gain Modulation of Quantum-Dot Semiconductor Optical Amplifiers.

The small-signal cross-gain modulation (XGM) characteristics of a p-doped quantum-dot (QD) semiconductor optical amplifier (SOA) are measured and compared with a theoretical model. The measured small-signal XGM responses show an average 3-dB bandwidth of 3.5 GHz and have no significant dependence on the pump-probe detuning wavelength. This indicates that the main XGM mechanism of the p-doped QD SOA is the total carrier density change rather than spectral hole burning. The measured small-signal conversion efficiency is compared with a theoretical model, which is derived from rate equations for QD SOAs. Based on our theoretical results, we find that the reduced intersubband (from the QD excited to ground state) carrier relaxation time due to p-type doping will decrease the small-signal 3-dB XGM bandwidth of QD SOAs [ABSTRACT FROM PUBLISHER]