1.8-W Room Temperature Pulsed Operation of Substrate-Emitting Quantum Cascade Lasers

High-power broad area substrate-emitting distributed feedback (DFB) quantum cascade laser emitting at λ ~ 4.6 μm is reported. Proper second-order DFB grating coupling, low waveguide loss mechanism, and epilayer-down mounting bring about a high vertical radiative optical power. The maximum peak power is as high as 1.82 W at 20 ^°C and still 1.22 W at 50 ^°C operated in pulsed mode with a pulsed width of 1 μs and duty cycle of 0.2%. A single-lobed radiation far-field with a divergence angle of 7.9 ^° in the ridge-width direction and two-lobed radiation far-field with a divergence angle of 0.61 ^° in the cavity-length direction are achieved by depositing the high-reflection coatings on both facets. Robust single-mode emission is continuously tunable by the heat sink temperature up to 115 ^°C.