OBSERVATION OF MODE BEATING AND SELF-FREQUENCY LOCKING IN A NEARLY SINGLE-MODE SEMICONDUCTOR-LASER

The beat spectra between the adjacent modes of a semiconductor laser h aving no external cavity are reported. Passive beat-frequency locking is observed at high power without a saturable absorber. This self-indu ced locking is manifested by the dramatic narrowing (by four orders of magnitude) of the beat spectrum between the dominant and adjacent mod es. It is accompanied by the transition from nearly single-mode behavi or to a highly structured multifrequency optical spectrum.