EXPERIMENTAL-EVIDENCE OF SINGLE ROUND-TRIP OSCILLATION IN POLARIZATION SELF-MODULATED VERTICAL-CAVITY SURFACE-EMITTING LASERS

The polarizations and frequencies of the two eigenstates of a vertical cavity surface emitting laser with an external cavity containing a qu arter-wave plate are theoretically and experimentally analyzed. It is shown that the polarizations of these eigenstates are fixed by the neu tral axes of the quarter-wave plate. The optical pulses at a frequency equal to a half of the free spectral range of the external cavity, ob served through a linear polarizer, are due to beats between the two ei genstates. All these features show that such polarization self-modulat ed lasers oscillate in a single round trip. (C) 1997 American Institut e of Physics.