SENSITIVITY TO EXTERNAL FEEDBACK FOR GAIN-COUPLED DFB SEMICONDUCTOR-LASERS

Performances of DFB semiconductor lasers with both index and gain spatial modulation are theoretically analysed in terms of threshold gain, emission wavelength, modal discrimination and sensitivity to external optical feedback. It is found that gain coupling provides low threshold gain, high spectral selection in favour of the mode oscillating at the Bragg wavelength with a relative immunity from facet reflection, and the sensitivity to external feedback is not significantly reduced in comparison with the case of pure index coupling.