Spectral properties of thermal fluctuations on simple liquid surfaces below shot noise levels

TL;DR

This paper investigates the spectral characteristics of thermal surface fluctuations on liquids, providing analytical insights and experimental validation at noise levels below shot noise, using a novel noise reduction technique.

Contribution

It offers new analytical descriptions of ripplon spectral functions and demonstrates their accuracy through experiments at unprecedented low noise levels.

Findings

Analytical spectral functions match experimental data well.

Thermal fluctuation spectra are accurately measured below shot noise.

The novel noise reduction method enables high-precision measurements.

Abstract

We study the spectral properties of thermal fluctuations on simple liquid surfaces, sometimes called ripplons. Analytical properties of the spectral function are investigated and are shown to be composed of regions with simple analytic behavior with respect to the frequency or the wave number. The derived expressions are compared to spectral measurements performed orders of magnitude below shot noise levels, which is achieved using a novel noise reduction method. The agreement between the theory of thermal surface fluctuations and the experiment is found to be excellent.