Using ensembles of dielectric nanoparticles in the FROG technique

We have implemented the FROG (frequency-resolved optical gating) technique for the characterization of ultrashort laser pulses in the range of tens of femtoseconds using ensembles of dielectric nanoparticles as the non-linear material for SHG (second-harmonic generation). In order to measure traces that could be retrieved with standard retrieval algorithms, a collinear configuration was needed to avoid undesirable effects from scattered light. The amplitude and phase of the retrieved pulses are in agreement with those obtained using BBO as nonlinear material. The large non-linear signals emitted by ensembles of nanoparticles and their low cost set them as an interesting alternative to autocorrelation to characterize ultrashort laser pulses in different spectral ranges. Since optical fiber lasers are now providing short pulses around tens of femtoseconds in many different spectral ranges, this field could greatly benefit from our findings. • Implementation of FROG using dielectric nanoparticles as SHG nonlinear material. • Collinear geometry avoids scattered photons to contribute the measured traces. • Alternative pulse characterization technique to autocorrelation for fiber lasers.