Nano-fabricated solid immersion lenses registered to single emitters in diamond

TL;DR

This paper presents a precise fabrication method for creating nano-structures around single quantum emitters in diamond, significantly enhancing photon collection efficiency for quantum applications.

Contribution

The authors develop a technique combining confocal microscopy and FIB etching for accurately fabricating structures around single diamond defects with nanometer precision.

Findings

8-fold increase in photon count rate after hemisphere fabrication

Positional accuracy of hundreds of nanometers in structure placement

Demonstration of improved photon collection efficiency in diamond defects

Abstract

We describe a technique for fabricating micro- and nano-structures incorporating fluorescent defects in diamond with a positional accuracy in the hundreds of nanometers. Using confocal fluorescence microscopy and focused ion beam (FIB) etching we first locate a suitable defect with respect to registration marks on the diamond surface and then etch a structure using these coordinates. We demonstrate the technique here by etching an 8 micron diameter hemisphere positioned such that a single negatively charged nitrogen-vacancy defect lies at its origin. This type of structure increases the photon collection efficiency by removing refraction and aberration losses at the diamond-air interface. We make a direct comparison of the fluorescence photon count rate before and after fabrication and observe an 8-fold increase due to the presence of the hemisphere.