Adjoint-optimized nanoscale light extractor for nitrogen-vacancy centers in diamond

TL;DR

This paper presents a novel nanoscale light extractor designed for efficient broadband light collection from nitrogen-vacancy centers in diamond, using adjoint optimization to achieve robust, high-enhancement outcoupling without damaging the diamond surface.

Contribution

The authors introduce a broadband, robust, and fabrication-tolerant nanoscale light extractor for NV centers, optimized via adjoint methods and applicable to other solid-state emitters.

Findings

Enhances optical power extraction by over 35 times.

Achieves beaming of emitted light into a +/-30° cone.

Design is robust to positioning and fabrication errors.

Abstract

We designed a nanoscale light extractor (NLE) for efficient outcoupling and beaming of broadband light emitted by shallow, negatively charged nitrogen-vacancy (NV) centers in bulk diamond. The NLE consists of a patterned silicon layer on diamond and requires no etching of the diamond surface. Our design process is based on adjoint optimization using broadband time-domain simulations and yields structures that are inherently robust to positioning and fabrication errors. Our NLE functions like a transmission antenna for the NV center, enhancing the optical power extracted from an NV center positioned 10 nm below the diamond surface by a factor of more than 35, and beaming the light into a +/-30{\deg} cone in the far field. This approach to light extraction can be readily adapted to other solid-state color centers.