Femtosecond self-diffraction as a measure of the nonlinear response spectrum

2025/10/29 by Assogna, Luca, Salvitti, Giovanna, Silvestri, Matteo +11
#FOS: Physical sciences #Optics (physics.optics)

paper · doi:10.48550/arxiv.2510.25267

Abstract

Self diffraction is a four-wave mixing process proportional to the square modulus of third-order nonlinearity susceptibility χ⁽³⁾, which is related to the material's electronic and thermal properties. In this study, we investigate the wavelength dependence of the self-diffracted signal generated by a femtosecond pulsed laser in a dye solution to directly evaluate the electronic third-order nonlinear susceptibility spectrum. By accounting for absorption effects and phase matching conditions, we determine the \vertχ⁽³⁾\vert for different concentrations. Experimental results complemented with theoretical predictions, show that in the low absorption and thin sample limits, the signal reproduce the \vertχ⁽³⁾\vert spectral profile. These findings demonstrate the feasibility of measuring nonlinear susceptibility spectra arising solely from the bound-electronic response across a wide spectral range and for various compounds.

Citations

• Dependence of the Nonlinear-Optical Response of Materials on their Linear ε and μ

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