50% continuous-wave wallplug efficiency from 1.53μm-emitting broad-area diode lasers

Abstract

Long-wavelength InP-based diode lasers emitting at 1.53 μm have been optimized for maximum continuous-wave (CW) electrical-to-optical power conversion efficiency, so-called wallplug efficiency (WPE). Efficient electron and hole capture into a single-quantum-well (SQW) active region as well as suppression of electron and hole leakage out of the SQW result in high values for the internal differential efficiency: ∼97% for long-cavity (≥2 mm) uncoated-facet devices and ∼85%–89% for short-cavity (1.5 mm) optimized facet-coated devices. The characteristic temperature of the slope efficiency, T1, reaches a high value of 323 K. Doping-level optimization of the p-cladding layer and the use of the SQW result in low values for the internal loss coefficient: ∼1.1 cm−1 for long-cavity (≥2 mm) uncoated-facet devices and ∼1.5–2.0 cm−1 for short-cavity (1.5 mm) optimized facet-coated devices. In turn, a maximum CW WPE value of 50% is achieved at room temperature and ∼1 W output power from conductively-cooled 100 μm-wide-aperture devices. The maximum CW power is 2.5 W. One beneficial byproduct of the CW-WPE maximization process is a large transverse spot size which, in turn, provides a very narrow transverse beamwidth: 26° full width half maximum. Reliability tests show no degradation when devices are run CW at high currents (4–5 A) and high temperatures (40–50 °C) for over 4000 h, at ∼2 W output power.