MODE-DISCRIMINATION IN DISTRIBUTED FEEDBACK GRATING SURFACE EMITTING LASERS CONTAINING A BURIED 2ND-ORDER GRATING

The operating characteristics of a novel grating surface emitting laser structure containing a buried second-order grating have been studied both experimentally and theoretically. This device consists of a pumped distributed feedback (DFB) section that is terminated at each end by unpumped distributed Bragg reflector sections. A single continuous second-order grating layer and waveguide layer extend throughout the active and passive sections so that there is essentially no fabricated optical discontinuity at the interface between the active and passive end sections. Single mode operation (> 30 dB side-mode suppression) and single-lobed far fields with negligible sidelobes are observed up to more than 5 x I(th) with spectral linewidths as narrow as 1 MHz. Natural mode selection of the uniform intensity mode occurs due to the gain-induced index depression in the active DFB section.