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 Delta upsilon approximate to 30 GHz for the carrier wavelength of 10 mu m, 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-mu m telecom diode laser as a pumping source. The wavelength of the optically tunable DFB QCL was modulated at frequencies up to 300 MHz.