Ultraviolet Mie resonances in computationally discovered boron phosphide nanoparticles

TL;DR

This paper identifies boron phosphide nanoparticles as promising ultraviolet Mie resonators through computational screening and experimental validation, enabling advanced UV nanophotonics.

Contribution

It introduces a systematic first-principles search for high-index materials and demonstrates UV Mie resonances in boron phosphide nanoparticles.

Findings

Boron phosphide exhibits high refractive index and low losses.

BP nanoparticles support Mie resonances at UV wavelengths.

Laser reshaping creates spherical BP nanoparticles with desired resonances.

Abstract

Controlling ultraviolet light at the nanoscale using optical Mie resonances holds great promise for a diverse set of applications, such as lithography, sterilization, and biospectroscopy. However, Mie resonances hosted by dielectric nanoantennas are difficult to realize at ultraviolet wavelengths due to the lack of both suitable materials and fabrication methods. Here, we systematically search for improved materials by computing the frequency dependent optical permittivity of 338 binary semiconductors and insulators from first principles, and evaluate their potential performance as high refractive index materials using Mie theory. Our analysis reveals several interesting candidate materials among which boron phosphide (BP) appears particularly promising. We then prepare BP nanoparticles and demonstrate that they support Mie resonances at visible and ultraviolet wavelengths using both far-field optical measurements and near-field electron energy-loss spectroscopy. We also present a laser reshaping method to realize spherical Mie-resonant BP nanoparticles. With a refractive index above 3 and low absorption losses, BP nanostructures advance Mie optics to the ultraviolet.