Recent efforts to improve the performance of mid-infrared antimonide-based semiconductor lasers have focused on enhancing the absorption of the pump beam to maximize power conversion efficiencies and minimize threshold intensities. One successful approach has been the optical pumping injection cavity (OPIC) laser, in which a type-II W active region is enclosed between distributed Bragg reflector (DBR) mirrors in order to achieve multiple passes of the pump beam and thereby to enhance absorption.
Previously, fixed wavelength sources have been used for optical pumping of OPIC laser structures, with limited tuning available by adjusting the incident angle. By tuning the pump wavelength using an optical parametric oscillator, we demonstrate minimum threshold intensities and maximum slope efficiencies at the resonance of the DBR cavity surrounding the active region, further demonstrating the potential of OPIC lasers. A 3.2 μm OPIC laser operated at 350 K in pulsed mode (at the highest operating temperature of the dewar), with a characteristic temperature of 50 K. The power conversion efficiency for a single facet at 300 K was the highest ever observed in the mid-IR, at approximately 4%.
Results are presented for two OPIC samples (emitting at ∼3.2 μm and 4.3 μm at high temperature), one of which was designed with a broadened cavity resonance, suitable for pumping with a multi-mode source. Threshold intensities and slope efficiencies measured as a function of pump wavelength demonstrate the strong resonance effect, and that the “broadened OPIC” does in fact manifest a much wider resonance than the non-broadened resonance cavity design.