Second-harmonic generation frequency-resolved optical gating in the single-cycle regime

Abstract

The problem of measuring broad-band femtosecond pulses by the technique of second-harmonic generation frequency-resolved optical gating (SHG FROG) is addressed. We derive the full equation for the FROG signal, which is valid even for single-optical-cycle pulses. The effect of the phase mismatch in the second-harmonic crystal, the implications of the beam geometry, and the frequency-dependent variation of the nonlinearity are discussed in detail. Our numerical simulations show that, under carefully chosen experimental conditions and with a proper spectral correction of the data, the traditional FROG inversion routines work well even in the single-cycle regime. The developed description of the SHG FROG signal was applied to measure the white-light continuum pulses in the spectral region of 500-1100 nm. The obtained spectral phase of these pulses served as a target function for the pulse compressor design. The pulses produced by compression around 800 nm were also characterized by SHG FROG. The resulting pulse duration measures 4.5 fs which corresponds to 2.5 optical cycles.

CEP stable 16 cycle laser pulses at 18 μm

“…The design took into account all considerations for characterization of few-cycle pulses, like for instance phase matching and temporal smear, as described by Baltuška et al [27]. A detailed description of the SHG-FROG apparatus can be found in Ref [21].…”

Cross-Correlation Frequency-Resolved Optical Gating for Test-Pulse Characterization Using a Self-Diffraction Signal of a Reference Pulse

“…This multichannel spectrometer is calibrated to compensate for the change in the spectral response. Phase matching of the SHG and SFG signals using the crystal needs to be considered [23]. Figure 2 shows the phase matching curve calculated by a homemade LabVIEW software (LabVIEW8.6, NATIONAL INSTRUMENTS, 2008, Austin, TX, USA) when using the 800 nm optical pulse as a reference pulse and a 5 µm BBO crystal.…”

Adaptive Femtosecond Quantum Control

“…The solution to this dilemma lies in employing the laser pulse itself, or a reference pulse of comparable duration, for the characterization of the pulse in phase and amplitude. Several different techniques have been developed for this purpose, among them FROG ("Frequency Resolved Optical Gating") [100][101][102], SI ("Spectral Interferometry") [103], SPIDER ("Spectral Phase Interferometry for Direct Electric Field Reconstruction") [104][105][106][107][108][109][110], and others, along with variations that are specifically designed for minimizing or augmenting certain inherent disadvantages of these techniques.…”