Complete Waveform Characterization of Mid-Infrared Ultrashort Pulses

Abstract

Development of ultrafast mid-infrared (MIR) pulse lasers has been in rapid progress over the past decade. Since a number of molecular vibrations have resonance in the MIR region, the ultrafast MIR pulse lasers are very useful for advanced molecular spectroscopies, such as frequency comb spectroscopy for the molecular fingerprint region, pump-probe spectroscopy to trace ultrafast structural dynamics, and control of photodissociation by selective excitation of vibrational states. The development of such a light source is also attracting more attention in the high field laser physics. The cutoff extension of high harmonic generation (HHG) driven by a long wavelength few-cycle pulse has been carried out, and generation of shorter attosecond pulses is predicted. Since it is a process within the single optical cycle of the driver electric field, it is very important to have a few-, single-, or sub-cycle pulse with a precisely controlled field oscillation, namely the phase control of the laser field within at least a few tenth of the oscillation period. In such an experiment, field-revolved detection of the ultrashort MIR pulses is essential since the cutoff of high harmonic generation is sensitive to the field strength of the driver laser pulse.