Optical loss suppression in long-wavelength semiconductor lasers at elevated temperatures by high doping of the n-waveguide

Abstract

We show that strong n-doping of the n-waveguide layer substantially decreases the thermal carrier leakage from the active layer and the associated optical losses in III-V semiconductor lasers. The effect is particularly pronounced in devices operating at the wavelength region where the free hole absorption cross-section is much greater than that of free electrons. This is predicted to decrease the threshold current and improve the output efficiency of the lasers. An example of a bulk InGaAsP/InP pulsed lasers is used to demonstrate that lasers with highly doped n-InGaAsP side of the waveguide can retain high output powers at ambient temperatures substantially above room temperature.

Optimization of a New GaN-Based Blue Laser Diode with a Quadruple Asymmetric Waveguide for High Efficiency Performance

“…However, at a very high injection current, the power roll-over has been observed in the broadened waveguide. Several suggestions have been offered for waveguide engineering to increase the laser diode output power [4]. Eventually, the employment of an asymmetric waveguide layer would be a way to balance the carrier confinement and high output power in LD design [5]- [8].…”

>25 W pulses from 1.5 μm double‐asymmetric waveguide, 100 μm stripe laser diode with bulk active layer

“…This effect was shown [12] to be a major limitation to the output power of the laser, and the most important one in the absence of laser heating, particularly in InGaAsP system materials used in the eye-safe spectral region devices since the free hole absorption cross-section σ h in these materials is almost two orders of magnitude higher than the free electron absorption cross-section σ e [13][14][15]. With this major loss mechanism minimized, an additional (more modest) decrease in optical losses at high currents was predicted to be achievable by increasing the doping of the n-side of the OCL [16], which was also shown to effectively suppress carrier accumulation in the waveguide caused by two-photon absorption [16] and by thermal spill-out from the AL [17].…”