Temporal characterization of femtosecond laser pulses using tunneling ionization

Abstract

Since its invention, laser has become essential tools in physical science, engineering, and medical science. The advances in ultrafast laser technology have helped the investigations of laser-matter interactions in the femtosecond time scale, which necessitated the comprehensive temporal characterization of laser pulses. Temporal characterization techniques based on the nonlinear response of optical materials have intrinsic limitations in their applications to measure laser pulses in a wide wavelength range and also to a few cycle laser pulses with very broad spectra. Instead of these frequency-domain techniques, the temporal characterization techniques operating in the time domain have been developed, but most techiques require the measurement in vacuum. In this thesis, we demonstrated a new pulse characterization method called the tunneling ionization with a perturbation for the time-domain observation of an electric field (TIPTOE) technique. Using a sub-cycle ionization burst as a fast temporal gate, it can directly measure a laser pulse in the time domain. We have studied ionization in ambient air, including the post processes after the ionization. A method to correctly measure an ionization yield in air was also developed. Then, the reconstruction algorithm developed for an accurate measurement was introduced. Furthermore, the temporal characterization of laser pulses covering from UV to IR was introduced. Finally, the signal-to-noise ratio of the TIPTOE measurement, which is critical to the pulse contrast measurement, is briefly discussed. Through this study, the TIPTOE method could be implemented in air and it was demonstrated that the femtosecond laser pulses can be accurately measured with the TIPTOE method.