Rapidly Tunable Quantum Cascade Lasers

Operation principles and designs of rapidly tunable quantum cascade lasers (QCL) were analyzed theoretically and experimentally. Theoretical analysis shows that by adding a special polarization transition with controllable intensity or energy to existing QCL designs, one can achieve emission frequency modulation Δυ ≈ 30 GHz for the carrier wavelength of 10 μm, while introducing additional optical losses of not more than 10 cm^-1 in the laser waveguide. Proof-of-principle electrically tunable QCL demonstrated frequency shift of 4.5 GHz. Rapid and continuous frequency tuning of a single-mode distributed-feedback quantum cascade laser (DFB QCL) by optical generation of electron-hole pairs in the laser waveguide and active area was demonstrated. Application of optimized pumping geometry made possible to achieve continuous tuning of a room-temperature-operated DFB QCL in the range of 0.6 cm ^-1 (20 GHz) using 1.3-μm telecom diode laser as a pumping source. The wavelength of the optically tunable DFB QCL was modulated at frequencies up to 300 MHz.