Optothermal nonlinearity of silica aerogel

TL;DR

This paper characterizes the thermal optical nonlinearity of silica aerogel, showing it has a nonlinear coefficient comparable to glass, which can be enhanced with dye embedding to surpass many traditional nonlinear materials.

Contribution

It provides the first detailed measurement of silica aerogel's optical nonlinearity and demonstrates enhancement through dye embedding.

Findings

Silica aerogel has a nonlinear optical coefficient similar to glass.

Embedding dye increases the nonlinear coefficient by two orders of magnitude.

The nonlinear absorption in silica aerogel remains negligible.

Abstract

We report on the characterization of silica aerogel thermal optical nonlinearity, obtained by z-scan technique. The results show that typical silica aerogels have nonlinear optical coefficient similar to that of glass $(\simeq 10^{-12} $m$^2/$W), with negligible optical nonlinear absorption. The non\-li\-near coefficient can be increased to values in the range of $10^{-10} $m$^2/$W by embedding an absorbing dye in the aerogel. This value is one order of magnitude higher than that observed in the pure dye and in typical highly nonlinear materials like liquid crystals.