Nonlinear optical responses of all-inorganic lead halide perovskite nanostructures by time-resolved beam-deflection technique

TL;DR

This study explores the nonlinear optical responses of inorganic lead halide perovskite nanostructures using a novel beam deflection technique, revealing thermal effects and higher nonlinear refractive indices than hybrid perovskites.

Contribution

It introduces a new method to measure nonlinear refraction in inorganic perovskites and demonstrates significantly higher nonlinear indices under near-resonant excitation.

Findings

Quantum dots show higher nonlinear refraction than nanosheets.

Thermal lensing dominates the nonlinear response.

Nonlinear refractive indices exceed those of hybrid perovskites.

Abstract

We have investigated nonlinear refraction in all-inorganic halide perovskites, the CsPbBr$_3$ and CsPbBr$_{1.5}$I$_{1.5}$ nanosheet and quantum dot colloids in toluene, by a novel beam deflection technique using near-resonant continuous wave lasers. The nonlinear refraction and its time-evolution measured here have originated from thermal lensing effect. Nonlinear behaviour of heat transport in terms of intensity dependent thermal diffusion rate has been observed. Effects of convective heat flow have been measured at high intensities. Quantum dots have higher nonlinear refraction as compared to the corresponding nanosheet samples, presumably due to reduced dimensionality. The effective values of nonlinear refractive index, estimated here for near-resonant excitations, exceed those reported in the literature for organic-inorganic hybrid perovskites in the nonresonant excitation regime, by several orders of magnitude.