Numerical and Experimental Characterization of Chirped Quantum Dot-based Semiconductor Optical Amplifiers

We present a model for the description of the dynamical behavior of Quantum Dot (QD) based Semiconductor Optical Amplifiers (SOAs) under injection of optical pulses. The model uses a Time Domain Traveling Wave (TDTW) approach to describe the optical field in the amplifier, and allows us to consider chirped QD materials by the inclusion of a set of rate equations modeling the occupation probability of the QD confined states in each active layer. The results of the numerical simulations are validated against experimental measurements of a two-contact chirped QD SOA with ground state emissions in the 1200 nm to 1300 nm range. When the single-pass configuration is compared to the double-pass setup, both the numerical simulations and the experimental results show that a clear improvement can be obtained with the latter configuration in terms of output power and signal amplification; for the majority of biasing conditions, the double-pass amplifier presents a gain approximately 3 dB greater than the single-pass without evident saturation of the gain and pulses broadening.