Modelling the effect of slave laser gain and frequency comb spacing on the selective amplification of injection locked semiconductor lasers

A rate equation model was used to model the optical filtering properties of injection locked semiconductor lasers. Numerical and experimental results are presented which show the changes in the comb rejection ratio (CRR) of an injection locked single mode laser due to the gain of the slave laser. It was found that there is an optimal slave laser current at which the CRR of the slave laser is largest, and good qualitative agreement is present between the model and experiment. The model was also used to predict the effects of the target carrier’s position on the optical comb. It was found that locking the slave laser to the outer comb lines gave slightly worse CRRs than when locking to the central lines. It is also shown that for comb frequency spacings close to the relaxation oscillation frequency of the slave laser, the obtainable CRR is significantly decreased.