Terahertz Nonlinear Index Extraction via Full-Phase Analysis

TL;DR

This paper demonstrates a method to measure the nonlinear refractive index and absorption in the terahertz regime using full-phase analysis, revealing significantly larger nonlinear indices in liquids than in the near-infrared.

Contribution

It introduces a full-phase analysis technique for extracting nonlinear optical properties in the terahertz range, providing new experimental data for liquids and vapors.

Findings

Nonlinear index of liquid water exceeds near-infrared values by six orders of magnitude.

Measured nonlinear index of water vapor at atmospheric pressure is 6x10^-11 cm^2/W.

Results confirm unexpectedly large nonlinear responses in the terahertz regime.

Abstract

We experimentally show the spectrally averaged nonlinear refractive index and absorption coefficient for liquid water, water vapor, {\alpha}-pinene, and Si using a full-phase analysis in the terahertz regime through a standard time-domain spectrometer. Our results confirm that the nonlinear index of refraction of the liquid samples in this regime exceeds the near-infrared optical nonlinear index by six orders of magnitude. In the case of liquid water and water vapor at atmospheric pressure, we find a nonlinear index of 7.8x10^-10 cm^2/W and 6x10^-11 cm^2/W respectively, which are both much larger than expected.