Angular Dependences of Third Harmonic Generation from Microdroplets

TL;DR

This paper investigates the angular dependence of third harmonic generation from water microdroplets, combining experimental measurements with advanced theoretical modeling to reveal stable intensity maxima near forward and backward directions.

Contribution

It introduces a nonlinear Mie theory extension to analyze THG in water droplets, providing new insights into angular emission patterns.

Findings

Stable intensity maxima near forward and backward directions

Good agreement between experiment and nonlinear Mie theory

Comparable intensity of THG in forward and backward directions

Abstract

We present experimental and theoretical results for the angular dependence of third harmonic generation (THG) of water droplets in the micrometer range (size parameter $62<ka<248$). The THG signal in $p$- and $s$-polarization obtained with ultrashort laser pulses is compared with a recently developed nonlinear extension of classical Mie theory including multipoles of order $l\leq250$. Both theory and experiment yield over a wide range of size parameters remarkably stable intensity maxima close to the forward and backward direction at ``magic angles''. In contrast to linear Mie scattering, both are of comparable intensity.