Coherent infrared spectroscopy system from terahertz to near infrared using air plasma produced by 10-fs pulses

We generated ultrabroadband coherent infrared pulses in a spectral range of 1-200 THz through the use of air plasma produced by hollow fiber compressed submillijoule 10-fs pulses and their second harmonics. Moreover, we coherently detected the electric-field profile in the range up to 150 THz through field-induced second harmonic generation of the probe in air. This result demonstrates the advantage of using air for detection, in terms of both spectral range and sensitivity, over photoconductive antennas and electro-optic (EO) sampling. The quadratic dependence of the signal sensitivity on the probe pulse energy shortens the effective probe pulse duration and contributes to the higher frequency detection than in the case of EO sampling with a crystal. (C) 2013 Optical Society of America