High-repetition-rate femtosecond mid-infrared pulses generated by nonlinear optical modulation of continuous-wave QCLs and ICLs.

We demonstrate an effective method to obtain high-repetition-rate femtosecond mid-infrared (mid-IR) pulses by nonlinear optical modulation of mid-IR continuous-wave (CW) quantum and interband cascade lasers (ICLs and QCLs). In the experiment, a high-repetition-rate femtosecond ytterbium-doped fiber laser with nanojoule-level pulse energy was used as the pump source of optical parametric amplifiers to modulate and amplify the mid-IR CW laser. Near transform-limited 84 fs duration (7.3 cycles) mid-IR pulses were generated with above 200 mW average power and a repetition rate of 160 MHz. Moreover, the spectral tunability was demonstrated using CW QCL at different wavelengths. The scheme offered a simple method to produce high-repetition-rate ultrashort pulses and that can be flexibly adopted in other mid-IR regions.