Simulation of mode-locked ring laser based on nonlinear polarization rotation in a semiconductor optical amplifier

We investigate numerically the generation of sub-picosecond optical pulses using a semiconductor optical amplifier (SOA) and a linear polarizer placed in a ring laser configuration. Nonlinear polarization rotation in the SOA is employed as the passive mode-locking mechanism. In particular attention is paid to the pulse narrowing process. We find that pulses as short as 300 femtoseconds can be generated if the dispersion is completely compensated. Our results are well in agreement with experimental results.