Folded-Cavity Surface-Emitting InGaAs-GaAs Lasers with Low-Threshold Current Density and High Efficiency

Folded-cavity surface-emitting InGaAs-GaAs lasers (FCSEL‘s) that employ high-quality internal 45° deflectors are demonstrated with low-threshold current density and high efficiency. A simplified process involving a stop etch to position the surface emitting output mirror close to the waveguide and lon-beam-etching (IBE) to form the 45° deflecting mirror is presented. FCSEL's (cavity length 800 µm) with two 45° deflectors, are obtained with threshold current density as low as 112.5 A/cm2 and surface-emission external quantum efficiency as high as 65 % (0.82 W/A). The additional loss contributed by the folded-cavity design is estimated as 4.2 cm-1.