High-power femtosecond mid-IR source with tunable center frequency and chirp

Abstract

We present an experimental implementation of a chirped mid-infrared (mid-IR) high-power laser source with variable center frequency between 4 and 30 THz and continuously tunable frequency sweep of up to 20% within one pulse, with a pulse duration of 2 ps. The peak electric field obtained at 4 THz is 1.5 MV/cm. We generate the mid-IR light using a difference-frequency generation process with two phase-locked, chirped IR pulses. The obtained mid-IR electric field waveform is characterized using electro-optic sampling. We compare our experimental results with the predictions of numerical simulations. The results indicate the potential for efficient driving of vibrational modes into a strongly anharmonic regime, in cases where using Fourier-transform-limited pulses to achieve similar vibrational amplitudes would lead to dielectric breakdown.