Abstract

In this work we present an experimental and theoretical study on high-order hyper-Rayleigh scattering (HRS). This process also called harmonic light scattering, is an incoherent variant of harmonic generation process which occurs in bulk crystals. In general, HRS is addressed in the literature to the lowest-order nonlinear (NL) processes of molecules or nanoparticles, i.e., second harmonic scattering in noncentrosymmetric materials and third harmonic scattering in centrosymmetric systems [1,2]. In the present work, we report the simultaneous emission of the second, third, fourth and fifth harmonic scattering in a sample consisting of beta barium borate (β-BBO) nanocrystals with dimensions of ≈10 nm. The optical excitation of the samples was performed at 2000 nm (100 fs pulses; repetition rate: 1.0 kHz), obtained via an OPA system pumped by a Ti:sapphire regenerative amplifier. The generated emission was observed at 1000 nm, 670 nm, 500 nm and 400 nm. In order to theoretically modeling the observed high-order optical harmonic generation and their dependence as a function of the excitation laser power, a generalized HRS approach was employed using the BBO second order properties as an internal self-reference parameter to quantify the high-order susceptibilities.

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