Improvement of Buried Grating DFB Quantum Cascade Lasers by Small-Angle Tapered Structure

Small-angle tapered waveguide structure combining with the sampled grating was adopted to improve the output power and achieve room temperature continuous-wave (CW) operation of buried grating distributed feedback quantum cascade lasers (DFB QCLs). By utilizing the first-order channel of sampled grating, single-mode DFB QCLs at four different wavelengths were fabricated simultaneously. At 298 K, all four devices can emit more than 130 mW optical power in CW operation. Fundamental transverse mode operation with excellent beam quality was preserved.