Large birefringence and linear dichroism in TiS3 nanosheets

TL;DR

This paper reports that TiS3 nanosheets exhibit exceptionally large birefringence and linear dichroism, making them promising for polarization-sensitive optoelectronic applications, supported by experimental measurements and ab initio calculations.

Contribution

The study provides the first detailed measurement of the complex refractive index of TiS3 nanosheets, revealing their superior birefringence and linear dichroism compared to traditional materials.

Findings

TiS3 nanosheets have larger birefringence than TiO2 and calcite.

The optical properties are consistent with excitonic effects.

Experimental results agree with ab initio calculations.

Abstract

TiS3 nanosheets have proven to be promising candidates for ultrathin optoelectronic devices due to their direct narrow band-gap and the strong light-matter interaction. In addition, the marked in-plane anisotropy of TiS3 is appealing for the fabrication of polarization sensitive optoelectronic devices. Herein, we study the optical contrast of TiS3 nanosheets of variable thickness on SiO2/Si substrates, from which we obtain the complex refractive index in the visible spectrum. We find that TiS3 exhibits very large birefringence, larger than that of well-known strong birefringent materials like TiO2 or calcite, and linear dichroism. These findings are in qualitative agreement with ab initio calculations that suggest an excitonic origin for the birefringence and linear dichroism of the material.