Optical feedback with stable and unstable external cavities

Summary form only given. The modulation frequency of the semiconductor laser in write strategies of optical recorders has become comparable to the relaxation oscillation frequency of the laser. Furthermore, the roundtrip time of the light from laser to optical disk and back corresponds to an external cavity mode spacing of similar frequency, i.e. ca. 2 GHz. In order to disentangle the role of the various time scales, we have investigated the influence of optical feedback on a high power semiconductor laser operating at 660 nm.