Nano-engineered Diamond Waveguide as a Robust Bright Platform for Nanomagnetometry Using Shallow Nitrogen Vacancy Centers

TL;DR

This paper introduces a nano-engineered diamond waveguide platform that significantly enhances photon collection from shallow nitrogen vacancy centers, boosting nanomagnetometry sensitivity and enabling advanced diamond-based quantum sensing applications.

Contribution

The study presents the first optimized tapered nano-waveguides directly fabricated on diamond, achieving record photon flux and preserving spin properties for improved quantum sensing.

Findings

Achieved a photon flux of ~1.7 million photons/sec from single NV centers.

Demonstrated no adverse effects on NV center spin coherence times.

Enhanced nanomagnetometry sensitivity by approximately five times.

Abstract

Photonic structures in diamond are key to most of its application in quantum technology. Here, we demonstrate tapered nano-waveguides structured directly onto the diamond substrate hosting shallow-implanted nitrogen vacancy (NV) centers. By optimization based on simulations and precise experimental control of the geometry of these pillar-shaped nano-waveguides, we achieve a net photon flux up to ~ $1.7 \cdot 10^6 /s$. This presents the brightest monolithic bulk diamond structure based on single NV centers so far. We observe no impact on excited state lifetime and electronic spin dephasing time ($T_2$) due to the nanofabrication process. Possessing such high brightness with low background in addition to preserved spin quality, this geometry can improve the current nanomagnetometry sensitivity ~ 5 times. In addition, it facilitates a wide range of diamond defects-based magnetometry applications. As a demonstration, we measure the temperature dependency of $T_1$ relaxation time of a single shallow NV center electronic spin. We observe the two-phonon Raman process to be negligible in comparison to the dominant two-phonon Orbach process.