Single-shot carrier-envelope-phase detection of few-cycle laser pulses using ionization in air

Abstract

The carrier-envelope-phase (CEP) of an ultrashort laser pulse is an important parameter for the description of laser-matter interactions. When a strong laser field irradiated on an atom, an electron can be tunneled out. Since the electron follows different pathways depending on CEPs, the CEP measurement has become a critical issue in strong-field physics and attosecond science. Several measurement techniques have been developed for the last 20 years. One of the commonly used techniques is an f-to-2f interferometer in which the CEP of a laser pulse is determined from interference between the laser pulse and its second harmonic pulse. The f-to-2f interferometer is a very efficient tool to produce a feedback signal to maintain a stable CEP. However, it can only measure relative changes in CEPs. It is hard to obtain an absolute CEP value. The other approach uses above-threshold-ionization (ATI) spectra measured using a stereo ATI spectrometer which enables the direct measurement of the absolute CEP. However, it is used in a limited number of applications since it requires massive vacuum equipment.

In this work, we present a new method for a CEP measurement using strong-field ionization in ambient air. Ionization yields produced by two-color laser fields are obtained at different relative phases. The ionization yields provide information on the absolute CEP value of the laser pulse. Since the method can be combined with a pulse characterization technique called TIPTOE, complete information on the incident laser pulse can be obtained. Also, it can be implemented using a relatively simple experiment setup because it operates in ambient air. Therefore, our approach will be used as an important tool for CEP measurements