Higher-order Kerr effect and harmonic cascading in gases

TL;DR

This paper investigates how higher-order harmonic cascading, especially from the third harmonic, influences the nonlinear refractive index in gases, revealing wavelength-dependent effects on the saturation intensity related to the higher-order Kerr effect.

Contribution

It demonstrates that cascaded third-harmonic generation creates a significant negative fifth-order nonlinearity, affecting the interpretation of HOKE saturation measurements in gases.

Findings

Cascaded third-harmonic generation results in a negative fifth-order nonlinearity.

Cascading effects modify the observed nonlinear index change.

Wavelength influences cascading impact on HOKE saturation intensity.

Abstract

The higher-order Kerr effect (HOKE) has been recently advocated to explain measurements of the saturation of the nonlinear refractive index in gases. Here we show that cascaded third-harmonic generation results in an effective fifth order nonlinearity that is negative and significant. Higher-order harmonic cascading will also occur from the HOKE, and the cascading contributions may significantly modify the observed nonlinear index change. At lower wavelengths cascading increases the HOKE saturation intensity, while for longer wavelengths cascading will decrease the HOKE saturation intensity.