High-speed modulation of a terahertz-frequency quantum-cascade laser using coherent acoustic phonon pulses

We demonstrate a new method for high-speed modulation of the electron transport and photon generation within a terahertz-frequency quantum-cascade laser (THz QCL). An amplified femtosecond laser is used to generate coherent acoustic-phonon pulses, which are injected into the device, resulting in an electronic bandstructure perturbation, with ~1-ns rise-time. The corresponding change in optical gain allows up to ~6% amplitude modulation, with results explained accurately using a perturbation-theory model.