Investigation of Tunable Single-Mode Quantum Cascade Lasers Via Surface-Acoustic-Wave Modulation

A novel distributed feedback quantum cascade laser (DFB-QCL) modulated by traveling surface acoustic wave (SAW) is proposed and theoretically studied. The device is based on a highly piezoelectric Zinc Oxide (ZnO) thin film applied directly on top of the QCL to enhance the SAW modulation of the device. To increase the coupling efficiency between the optical lasing mode and the SAW-induced DFB grating, air-waveguide and surface plasmon waveguide structures with two-section active regions are proposed. Simulation results show that a moderate coupling coefficient of ~ 2.5 cm^-1 can be achieved for the structures, assuming high quality piezoelectric material and device fabrication can be achieved. The proposed scheme may provide a potentially alternative approach to achieve single-mode, tunable QCLs.