Dynamics of Semiconductor Lasers Under External Optical Injection

摘要

Injection of an external optical signal into the oscillating mode of asemiconductor laser can modify the coupling between the circulating optical field and the carrier density (gain medium). The external optical signal modifies both the gain and the refractive index of the semiconductor gain medium by changing the free-carrier density. Depending on the strength of the optical injection and the frequency offset between the injected signal and the free-running oscillation frequency, this can lead to modulated output including multiwave mixing, unstable dynamics, and deterministic chaos, or to significantly improved modulation and noise characteristics relative to the free-running case. Experimental investigations were coupled with numerical and analytical modeling to investigate the modified output in a commercially available laser diode and a vertical-cavity surface-emitting laser (VCSEL). The modeling used a conventional coupled-equation model which, we found, identifies the key phenomena that we observe in our data.