Design and Focused Ion Beam Fabrication of Single Crystal Diamond Nanobeam Cavities

TL;DR

This paper designs high-Q, small mode volume nanobeam photonic crystal cavities in single crystal diamond for quantum applications, and demonstrates two focused ion beam fabrication methods to realize these structures.

Contribution

It introduces a novel design for diamond nanobeam cavities with high quality factors and demonstrates two FIB fabrication strategies to produce them from bulk diamond.

Findings

Achieved a high Q (~10^6) and small mode volume (~0.5 ({ lambda}/n)^3) in the design.

Demonstrated two FIB fabrication methods: side-milling and lift-off.

Discussed fabrication challenges impacting high-Q/V realization.

Abstract

We present the design and fabrication of nanobeam photonic crystal cavities in single crystal diamond for applications in cavity quantum electrodynamics. First, we describe three-dimensional finite-difference time-domain simulations of a high quality factor (Q ~ 10^6) and small mode volume (V ~ 0.5 ({\lambda}/n)^3) device whose cavity resonance corresponds to the zero-phonon transition (637nm) of the Nitrogen-Vacancy (NV) color center in diamond. This high Q/V structure, which would allow for strong light-matter interaction, is achieved by gradually tapering the size of the photonic crystal holes between the defect center and mirror regions of the nanobeam. Next, we demonstrate two different focused ion beam (FIB) fabrication strategies to generate thin diamond membranes and nanobeam photonic crystal resonators from a bulk crystal. These approaches include a diamond crystal "side-milling" procedure as well as an application of the "lift-off" technique used in TEM sample preparation. Finally, we discuss certain aspects of the FIB fabrication routine that are a challenge to the realization of the high-Q/V designs.