FEEDBACK PHENOMENA IN A SEMICONDUCTOR-LASER INDUCED BY DISTANT REFLECTORS

An indepth experimental investigation of reflection-induced behavior of a semiconductor laser reveals many different phenomena, some previously unknown. We have identified and made a description of 1) multiple pass resonances in the noise spectrum, 2) low frequency self-oscillations in asymmetric geometrical configurations, 3) the double peaked structure of the external cavity resonance f(c) (at c/2L), 4) the ''subharmonic cascading'' from f(c) and 5) the generation of subharmonics of a modulated injection current. The exact field intensity distribution in the passive external resonator is shown to command these phenomena which reveal intermingled spatial and dynamical effects. The different behaviors are related to the characteristic curves of the laser. We have found that when the external cavity laser operates in its unstable regime, a locking of the otherwise randomly distributed intensity drops can occur giving a narrow resonance in the noise spectrum. In addition, based on our observations, adapted rate equations are built starting from the Lang and Kobayashi model. Our results show an adequate match between theory and experiments for the detailed microwave spectra, multiple pass resonances of the external cavity, as well as low frequency resonances.