High-performance bound-to-continuum quantum-cascade lasers for broad-gain applications

Based on the bound-to-continuum active region design, we shall present a high performance continuous-wave (CW) quantum-cascade laser. In contrast to high performance lasers based on a two-phonon resonance transition and a narrow linewidth (< 165 cm(-1)), the device presented here exhibits a spontaneous emission full-width at half-maximum as large as 295 cm(-1). Thus, such devices are very suitable for broadband tuning. At 30 degrees C, it shows a maximum output power and slope efficiency of 188 mW and 500 mW/A, as well as a threshold current density of only 1.79 kA/cm(2). Furthermore, at this temperature, the device demonstrates an internal differential quantum efficiency of 71% and a wallplug efficiency of 2.0%. The maximum CW operation temperature reached is 110 degrees C. A thermal resistance of 4.3 K/W was attained by epi-down mounting on diamond submounts. The waveguide losses of 14 cm(-1) are explained by intersubband absorption in addition to free-carrier absorption.