Diamond parabolic reflectors for nanoscale quantum sensing

The nitrogen-vacancy (NV) center in diamond is an atomic-scale atom-like system with an electronic spin that can be initialized and detected optically, making it an exceptional system for quantum sensing of magnetic phenomena requiring high field sensitivity, fine spatial resolution, quantitative imagery [1, 2]. A particularly powerful approach is to incorporate the NV sensor in a scanning probe, allowing for nanometer spatial resolution. Key challenges for such a system are to ensure high collection efficiency and NV-sample spacing below a few 10s of nm.

We address these challenges with all-diamond parabolic scanning probes containing single NVs. The parabolic shape redirects 80% of the NV emission into a strongly collimated mode [3]. To achieve a small NV-sample spacing we truncate the probe apex such that the NV sits at the focus of the parabola for optimal collection efficiency while achieving a tip-to-sample spacing of < 50 nm. We demonstrate the performance of these scanning probes through magnetometry on antiferromagnetic, thin-film Cr₂O₃ [4].

[1] Casola, F., van der Sar,T., Yacoby, A., Nat. Rev. Mat. 3, 17088 (2018)
[2] Rondin, L., et al., Reports on Progress in Physics, 77, 5 (2014)
[3] Wan, N., et al., Nano Lett. 18, 5 (2018)
[4] Appel, P., et al., Nano Lett. 19, 3 (2019)