Coupled Ridge Waveguide Substrate-Emitting DFB Quantum Cascade Laser Arrays

A coupled ridge waveguide substrate-emitting quantum cascade laser array operating at λ ~ 7 μm was presented. Fifteen elements were integrated in parallel to get high peak power and improved beam quality. The device was operating at fundamental supermode with a single-lobed far-field pattern. A narrow divergence angle of 2.9° in the ridge-width direction and 0.36° in the cavity-length direction were obtained by carefully designing the coupled ridge waveguide structure. Single-mode emission was observed by employing a buried second-order distributed-feedback grating. The peak power of the device was more than 2 W in pulsed operation at room temperature. This letter showed great potential to enlarge the output power of the surface-emitting devices while maintaining good beam quality.