# Nonlinear elasticity of silica nanofiber

## TL;DR

This paper explores the nonlinear elastic behavior of silica nanofibers under high tensile strain, revealing significant changes in elastic wave properties and proposing their potential for advanced optical strain sensors.

## Contribution

It provides the first comprehensive experimental and theoretical analysis of nonlinear elasticity effects in silica nanofibers at high strain levels.

## Key findings

- Elastic wave properties change dramatically beyond 2% strain.
- Brillouin strain coefficients are unexpectedly high.
- Theoretical analysis aligns well with experimental results.

## Abstract

Optical nanofibers (ONFs) are excellent nanophotonic platforms for various applications such as optical sensing, quantum and nonlinear optics, due to both the tight optical confinement and their wide evanescent field in the sub-wavelength limit. Other remarkable features of these ultrathin fibers are their surface acoustic properties and their high tensile strength. Here we investigate Brillouin light scattering in silica-glass tapered optical fibers under high tensile strain and show that the fundamental properties of elastic waves dramatically change due to elastic anisotropy and nonlinear elasticity for strain larger than 2%. This yields to unexpected and remarkable Brillouin strain coefficients for all Brillouin resonances including surface and hybrid waves, followed by a nonlinear evolution at high tensile strength. We further provide a complete theoretical analysis based on third-order nonlinear elasticity of silica that remarkably agrees with our experimental data. These new regimes open the way to the development of compact tensile strain optical sensors based on nanofibers.