Free-standing silicon nitride nanobeams with efficient fiber-chip interface for cavity QED

TL;DR

This paper reports the development of high-Q silicon nitride nanobeam photonic crystal cavities at visible wavelengths, coupled efficiently to fiber interfaces, enabling advanced cavity QED experiments with diamond color centers.

Contribution

It introduces a novel fabrication and characterization approach for high-Q nanobeam cavities with an efficient fiber coupling platform for cavity QED applications.

Findings

Achieved a quality factor of about 24,000 at the zero-phonon line of diamond centers.

Demonstrated a fiber-to-waveguide coupling efficiency of approximately 96%.

Enabled efficient integration of nanophotonic cavities with fiber interfaces.

Abstract

We present the design, fabrication and characterization of high quality factor silicon nitride nanobeam PhC cavities at visible wavelengths for coupling to diamond color centers in a cavity QED system. We demonstrate devices with a quality factor of about 24;000 around the zero-phonon line of the germanium-vacancy center in diamond. We also present an efficient fiber-to-waveguide coupling platform for suspended nanophotonics. By gently changing the corresponding effective indices at the fiber-waveguide interface, we achieve an efficiency of about 96% at the cavity resonance.