High-speed, low-threshold InGaAsP semi-insulating buried crescent lasers

The authors describe the refinement of this laser structure for high-speed operation and record bandwidths for a planar structure. To achieve bandwidths in excess of 20 GHz, it is necessary to increase the slope of the resonance frequency vs. output power so that higher bandwidths are achieved at lower bias currents. This is accomplished by reducing the active channel width to 1 mu m, by p-doping the active layer, and by cleaving cavity lengths as short as 100 mu m. In addition, the parasitic capacitance is further reduced by limiting the p-contact width to 12 mu m, and by the use of a thick polyimide layer under the bond pad metal. Lasers fabricated in this manner exhibited thresholds as low as 6 mA, with maximum output powers of 15 mW per facet at 100 mA bias current. The total differential quantum efficiency was typically 45-55%.<>