Interferometric time-domain ptychography for ultrafast pulse characterization

Ptychography, a phase retrieval method originally developed for crystallography [1], was recently adapted from real space imaging to the temporal domain for the characterization of ultrashort laser pulses [2]. Since then, several time-domain ptychography (TDP) pulse characterization schemes have been proposed and demonstrated, bearing experimental similarities, e.g., to second-harmonic frequency-resolved optical gating (FROG) [2-5], and attosecond streaking [6]. Of these, the best suited method for few-cycle pulses in the optical range is based on noncollinear FROG [3]. Here we demonstrate a collinear adaptation of TDP, and use it to characterize unamplified 12-fs pulses with a carrier wavelength of 800 nm from a Ti:sapphire oscillator. We call the method interferometric ptychographic intensity-gated laser pulse E(t) reconstruction (iPIGLET). The use of a collinear beam geometry is preferred over a noncollinear one for few-cycle pulses with low pulse energy, as this allows higher peak intensities to be reached through tighter focusing. Furthermore, the use of a collinear geometry avoids the geometrical smearing effect, which can detrimentally affect the retrieved pulse shape.