Buried heterostructure quantum cascade lasers with high continuous-wave wall plug efficiency

The authors report on the development of $\lambda \sim 4.7\mu \mathrm{m}$ strain-balanced InP-based quantum cascade lasers with high wall plug efficiency and room temperature continuous-wave operation. The use of narrow-ridge buried heterostructure waveguides and thermally optimized packaging is presented. Over 9.3% wall plug efficiency is reported at room temperature from a single device producing over $0.675\mathrm{W}$ of continuous-wave output power. Wall plug efficiencies greater than 18% are also reported for devices at a temperature of $150\mathrm{K}$ , with continuous-wave output powers of more than $1\mathrm{W}$ .