Deep-etched distributed Bragg reflector lasers with curved mirrors.Experiments and modeling

摘要

A semiconductor laser with deep-etched distributed Braggnreflectors (DBRs) supporting a planar Gaussian mode has beennexperimentally and theoretically studied. A 90-Μm-long laser withntwo-groove DBRs has a low threshold current of 7 mA and a maximum sidenmode suppression of 17.6 dB under continuous operation. The lasernresonator supports a mode that closely resembles the desired planarnGaussian mode. The reflectivities of the deep-etched DBRs werenexperimentally determined using broad area devices, and the reflection,ntransmission, and scattering properties of the DBRs were simulated usingna finite-difference time-domain model. The simulations show that deepngrooves, covering the full transverse extent of the guided mode, arenneeded to maximize the reflectivity and to minimize the scattering loss.nA beam-propagation model was used to simulate the laser resonator. Thensimulations (as well as the experiments) show that the laser isnsensitive to thermal effects. Thermal lensing narrows the mode waist,nand therefore increases the spatial hole burning in the center of thenresonator where the intensity is at its maximum. At high drive currents,nthis leads to a degradation of the spatial mode quality. The simulationsnalso indicate that a laser with optimized DBRs (one one- and onentwo-groove DBRs with an etch depth of 1 Μm) would have a thresholdncurrent less than 2 mA and support a high-quality planar Gaussian modento an output power of 9 mW under continuous operation