Room temperature continuous operation of vertical cavity microlasers

Abstract

The microlaser structure has a top p-doped mirror, a full wave thick spacer with three InGaAs quantum wells, and an n-doped bottom mirror, all grown by molecular beam epitaxy. The structure was designed for 980 nm. Chemical beam ion-beam assisted etching was used to generate various sizes of square mesas (5, 10, 25, 50, 100, 200 µm). Deep (5-µm deep) and shallow (2.5-µm deep) etchings were tried and compared. Shallow etched samples generally showed better thermal and spectral characteristics. Pulsed threshold currents are the same for both. Continuous lasing was observed for 10- and 25-µm mesas with 4- and 13-mA current, respectively. In pulsed operation, the threshold currents are 2.0,4.0,10,30,120 mA for 5-, 10-, 25-, 50-, 100-µm mesas, respectively. For mesas smaller than 25 µm, the threshold current increases linearly with mesa linear dimension. This linear dependence is explained by a strong surface recombination for these small mesas. For the larger ones, the threshold current increases linearly with mesa area at 1.2 kA/cm2. With this current density and proper passivation of the side walls of the smaller mesas, one should achieve 300-µA threshold current for a 5-µm mesa. The maximum peak power was 86 mW from a 100-µm mesa at 980 nm.