Giant optical anisotropy in transition metal dichalcogenides for next-generation photonics

TL;DR

This paper reports exceptionally high optical anisotropy in transition metal dichalcogenides, especially MoS2, across infrared and visible spectra, opening new possibilities for advanced photonic devices.

Contribution

It demonstrates unprecedented birefringence in TMDCs, validated by experiments and first-principles calculations, advancing the understanding of their optical properties for photonics.

Findings

Birefringence of 1.5 in infrared for MoS2

Birefringence of 3 in visible light for MoS2

Potential for overcoming diffraction limits in photonics

Abstract

Large optical anisotropy observed in a broad spectral range is of paramount importance for efficient light manipulation in countless devices. Although a giant anisotropy was recently observed in the mid-infrared wavelength range, for visible and near-infrared spectral intervals, the problem remains acute with the highest reported birefringence values of 0.8 in BaTiS3 and h-BN crystals. This inspired an intensive search for giant optical anisotropy among natural and artificial materials. Here, we demonstrate that layered transition metal dichalcogenides (TMDCs) provide an answer to this quest owing to their fundamental differences between intralayer strong covalent bonding and weak interlayer van der Walls interaction. To do this, we carried out a correlative far- and near-field characterization validated by first-principle calculations that reveals an unprecedented birefringence of 1.5 in the infrared and 3 in the visible light for MoS2. Our findings demonstrate that this outstanding anisotropy allows for tackling the diffraction limit enabling an avenue for on-chip next-generation photonics.