Interferometric Autocorrelation of an Attosecond Pulse Train in the Single-Cycle Regime

Abstract

We report on the direct observation of the phase locking of the attosecond pulse train (APT) via interferometric autocorrelation in the extreme ultraviolet region. APT is formed with Fourier synthesis of high-order harmonic fields of a femtosecond laser pulse. Time-of-flight mass spectra of N+, resulting from the Coulomb explosion of N2 absorbing two photons of APT, efficiently yield correlated signals of APT. The measured autocorrelation trace exhibits that the duration of the pulse should be only 1.3 periods of the extreme ultraviolet carrier frequency. A few interference fringes within the short pulse duration clearly show two types of symmetry, which ensure the phase locking between pulses in APT.

Photoelectron Angular Distribution and Phase in Two-Photon Single Ionization of H and He by a Femtosecond and Attosecond Extreme-Ultraviolet Pulse

“…Photoelectron angular distribution is nowadays extensively studied by the velocity map imaging technique (see e.g., [29,30]). These new light sources have also enabled two-photon ionization (2PI) of species with a deep ionization potential such as He [31][32][33][34][35] and N 2 [36].…”

The simplest route to generating a train of attosecond pulses

“…2 In recent years, through the powering of such attosecond laser sources, 21 nonlinear optics in the attosecond regime are also being explored. 22,23 These studies have mainly been executed in the extreme ultraviolet regime. On the other hand, in closely related studies in the near-infrared-visible-ultraviolet range, curious new approaches based on four-wave mixing in whispering-gallery-mode microresonators 24,25 or the adiabatic excitation of Raman transitions [26][27][28][29][30][31][32][33][34][35][36][37][38][39] are being extensively examined to generate broad, discrete, coherent spectra spanning over an octave and then manipulate them.…”

Spatiotemporal characterization of single-order high harmonic pulses from time-compensated toroidal-grating monochromator

“…Among these opportunities, high harmonics, which are generated by the interaction between ultrashort laser pulses and rare gases, appear to be promising for spectroscopy because of the compactness of their experimental apparatus and their ultrashort temporal durations that break into the attosecond regime [4][5][6][7][8]. High harmonics can now realize the direct observation of the dynamics in atoms, molecules, and solid-state materials with femtosecond and attosecond temporal resolution [9][10][11][12][13][14].…”