High-average-power, high-duty-cycle (λ∼6 μm) quantum cascade lasers

High-power quantum cascade lasers emitting at $\text{λ=6.1\hspace{0.17em}μ}\mathrm{m}$ are demonstrated. Accurate control of growth parameters and strain balancing results in a near-perfect lattice match, which leads to excellent material quality. Excellent peak power for uncoated lasers, up to 1.5 W per facet for a 21 μm emitter width, is obtained at 300 K for 30 period structures. The threshold current density at 300 K is only 2.4 kA/cm². From 300 to 425 K, the laser exhibits a characteristic temperature $T_0$ of 167 K. Next, ${\mathrm{Y}}_2{\mathrm{O}}_3/\mathrm{Ti/Au}$ mirror coatings were deposited on 1.5 mm cavities and mounted epilayer down. These lasers show an average output power of up to 225 mW at 17% duty cycle, and still show 8 mW average power at 45% duty cycle.