Optical Measurement of Mass Density of Biological Samples

TL;DR

This paper introduces a novel all-optical method using stimulated Brillouin scattering to accurately measure the mass density of biological samples, overcoming limitations of previous techniques.

Contribution

It demonstrates that nonlinear gain in stimulated Brillouin scattering can be used to reliably estimate biological mass density, surpassing traditional refractive index-based methods.

Findings

Reduces mass density estimation error tenfold

Provides a more accurate and universal measurement technique

Shows that refractive index alone is insufficient for density determination

Abstract

Mass density is a vital property for improved biophysical understanding of and within biological samples. It is increasingly attracting active investigation, but still lacks reliable, non-contact techniques to accurately characterize it in biological systems. Contrary to popular belief, refractive index information alone is insufficient to determine a sample's mass density, as we demonstrate here theoretically and experimentally. Instead, we measured the nonlinear gain of stimulated Brillouin scattering to provide additional information for mass density estimation. This all-optical method reduces the estimation error tenfold, offering a more accurate and universal technique for mass density measurements.