Direct Reconstruction of Two Ultrashort Pulses Based on Non-Interferometric Frequency-Resolved Optical Gating

While interferometric pulse measurement techniques usually employ direct, i.e. analytical reconstruction algorithms, this is rarely the case with non-interferometric techniques. Classical non-interferometric pulse characterization techniques such as FROG have been using iterative reconstruction algorithms for decades [1]. Convergence tests have been conducted, memetic algorithms have been used, and even deep neural network techniques have been applied. More recent non-interferometric pulse measurement techniques, such as dispersion-scan (d-scan), also use iterative reconstruction algorithms [2]. In order to approach the problems associated with convergence in non-interferometric techniques, this work presents a fully non-interferometric pulse characterization technique that reconstructs amplitudes and phases of two input pulses, from two different FROG spectrograms using a direct reconstruction algorithm [3]. This direct and analytical algorithm is evidently very fast and completely bypasses the convergence issue, thus presenting a significant difference to conventional FROG, d-scan and other non-interferometric techniques. The two different FROG spectrograms are measured with a single-shot FROG setup. To demonstrate and determine the reconstruction quality for complex pulses, a programmable pulse shaper is used to modify the pulses sourced from a Kerr-lens mode-locked Ti:sapphire oscillator.