SPATIAL AND TEMPORAL COHERENCE OF BROAD-AREA LASERS WITH GRATING FEEDBACK

When a broad-area semiconductor Laser (BAL) is operated near threshold or at moderate current, experimental results show that grating feedba ck (GF) can destabilize the spatial mode structures even though the fr equency bandwidth is actually compressed by a factor of 45. Yet at hig her injection currents (>2.5I/I-th), because the free-running BAL alre ady exhibits severe filamentation, GF has little influence on the spat ial modes, even though the spectral width continues to be compressed b y the same factor. This behavior is suggested by the measurement of in tensity noise versus pump current. (C) 1998 Optical Society of America [S0740-3224(98)01709-3].