Femtosecond-laser-pulse characterization and optimization for CARS microscopy

TL;DR

This paper introduces a straightforward, sample-level method for characterizing and optimizing femtosecond laser pulses in CARS microscopy, enhancing spectral resolution and contrast without additional equipment.

Contribution

It provides a novel experimental approach to determine pulse characteristics directly at the sample, using existing delay lines and nonlinear signals, without extra autocorrelators.

Findings

Accurately measures pulse duration and chirp at the sample level.

Improves spectral resolution and contrast in CARS imaging.

Eliminates need for additional autocorrelators.

Abstract

We present a simple method and its experimental implementation to completely determine the characteristics of the pump-and-probe pulse and the Stokes pulse in a coherent anti-Stokes Raman scattering microscope at sample level without additional autocorrelators. Our approach exploits the delay line, ubiquitous in such microscopes, to perform a convolution of the pump-and-probe and Stokes pulses as a function of their relative delay and it is based on the detection of the photons emitted from an appropriate non-linear sample. The analysis of the non-resonant four-wave-mixing and sum-frequency-generation signals allows retrieving the pulse duration on the sample and the chirp of each pulse. This knowledge is crucial in maximizing the spectral-resolution and contrast in CARS imaging.