Jitter dynamics of a gain switched semiconductor laser under self-feedback and external optical injection

We investigate the jitter dynamics of a gain switched laser diode (LD) under the influence of strong optical injection due either to multiple reflections from an external cavity mirror, or from another LD. A numerical technique that considers both the spontaneous emission noise and multiple reflections from external optical components is implemented. At all times, the LD exhibits multi-longitudinal mode operation with a Gaussian-shaped spectral line profile that is centered around a fixed dominant output wavelength. We separately consider three (strong) optical injection conditions: 1) coherent self-feedback; 2) incoherent self-feedback; and 3) coherent, external continuous-wave (CW) optical injection. Incoherent self-feedback results in a reduction, by an order of magnitude, in both the intensity and timing jitter (0.5 ps), while maintaining the average peak power and pulsewidth. Eye pattern results show an opening of at least 90 %, which represents an improvement by a factor of two over the same LD that operates without optical injection. The external CW injection condition approaches that of incoherent self-feedback only at high external injection. Coherent self-feedback does not produce any significant change in the LD performance.