Generation of intense highly coherent femtosecond pulses in the mid infrared

Highly coherent mid-infrared femtosecond pulses, tunable between 2.5 and 4.4 μm, and with an average energy and duration between 2.6 and 3.6 μm of 11 μJ and 200 fs, respectively, have been produced by an optical parametric amplifier setup driven at 1 kHz by a 400-μJ, 800-nm pulse from a Ti:sapphire amplifier. In this system, first tunable moderate-energy femtosecond pulses in the near infrared are produced by continuum amplification in β-barium borate, and subsequently the near-infrared pulses are amplified and frequency mixed with 800-nm radiation in potassium titanyl phosphate to produce intense tunable mid-infrared pulses. The time-bandwidth product of the mid-infrared pulses is 0.28 ± 0.02 over the whole high-energy tuning range. Experimental results are compared with numerical simulations and a simple model.