Direct ultrashort-pulse intensity and phase retrieval by frequency-resolved optical gating and a computational neural network.

Ultrashort-laser-pulse retrieval in frequency-resolved optical gating has previously required an iterative algorithm. Here, however, we show that a computational neural network can directly and rapidly recover the intensity and phase of a pulse.

Ultrashort-pulse measurement using noninstantaneous nonlinearities: Raman effects in frequency-resolved optical gating.

Ultrashort-pulse-characterization techniques generally require instantaneously responding media. We show that this is not the case for frequency-resolved optical gating (FROG). We include, as an example, the noninstantaneous Raman response of fused silica, which can cause errors in the retrieved pulse width of as much as 8% for a 25-fs pulse in polarization-gate FROG. We present a modified pulse-retrieval algorithm that deconvolves such slow effects and use it to retrieve pulses of any width. In experiments with 45-fs pulses this algorithm achieved better convergence and yielded a shorter pulse than previous FROG algorithms.

Measuring the spatial coherence from an extended quasi-monochromatic source by double-exposure speckle interferometry.

Double-exposure speckle interferometry is used to measure the degree of spatial coherence from an extended quasi-monochromatic source. The method closely follows the theory of spatial coherence and allows easy interpretation of results; it can be implemented with a compact interferometer based on laser speckle patterns.