LATERALLY-COUPLED DISTRIBUTED-FEEDBACK LASER FABRICATED WITH ELECTRON-BEAM LITHOGRAPHY AND CHEMICALLY ASSISTED ION-BEAM ETCHING

The fabrication and optical performance of Laterally-Coupled Distribut ed Feed-Back (LC-DFB) lasers were investigated. This device differs fr om a conventional DFB laser in that the grating does not extend inside the laser ridge, rather, gratings adjacent to a single ridge are used to couple to the fringing fields of the active region. This structure allows the entire laser epi-layer structure to be grown in a single s tep thus eliminating any regrowth steps. A recent design with 1.5 mm c avity length and CAIBE-defined ridges and gratings resulted in pulsed single-mode operation up to 36 mW at 937 nm with as-cleaved facets. Th e light-current characteristic of this device demonstrated a threshold current of 15 mA and a sidemode suppression ratio of greater than 30 dB. The spectral temperature sensitivity was 0.65 Angstrom/degrees-C f or this LC-DFB. Also a CW threshold current of 25 mA and an external q uantum efficiency of 0.48 mW/mA per facet were measured for a 1 mm cav ity length device with anti-reflection coated facets. Fabrication proc esses and optical characterization are discussed.