Fabrication and characterization of high quality factor silicon nitride nanobeam cavities

TL;DR

This paper reports the fabrication and detailed characterization of silicon nitride nanobeam cavities with high quality factors suitable for nanophotonic applications involving diamond NV centers, achieving significant improvements in resonance tuning.

Contribution

It introduces a fabrication process for high-Q Si3N4 nanobeam cavities with tunable resonances, advancing nanophotonics at visible wavelengths.

Findings

Quality factors up to Q ~ 55,000 achieved

Cavity resonances tunable across 600-700nm

Order of magnitude improvement over previous SiNx cavities

Abstract

Si3N4 is an excellent material for applications of nanophotonics at visible wavelengths due to its wide bandgap and moderately large refractive index (n $\approx$ 2.0). We present the fabrication and characterization of Si3N4 photonic crystal nanobeam cavities for coupling to diamond nanocrystals and Nitrogen-Vacancy centers in a cavity QED system. Confocal micro-photoluminescence analysis of the nanobeam cavities demonstrates quality factors up to Q ~ 55,000, which is limited by the resolution of our spectrometer. We also demonstrate coarse tuning of cavity resonances across the 600-700nm range by lithographically scaling the size of fabricated devices. This is an order of magnitude improvement over previous SiNx cavities at this important wavelength range.