# A Fiber-coupled Scanning Magnetometer with Nitrogen-Vacancy Spins in a Diamond Nanobeam

## TL;DR

This paper introduces a fiber-coupled diamond nanobeam sensor with nitrogen-vacancy spins for high-efficiency optical magnetic imaging, suitable for challenging environments like cryostats or biological systems.

## Contribution

It presents a novel scanning-NV sensor design that integrates a diamond nanobeam with tapered optical fiber for efficient optical access and magnetic sensing.

## Key findings

- Demonstrated through-fiber optically interrogated electron spin resonance.
- Achieved proof-of-principle magnetometry by imaging spin waves.
- Sensor design enables operation in challenging environments.

## Abstract

Magnetic imaging with nitrogen-vacancy (NV) spins in diamond is becoming an established tool for studying nanoscale physics in condensed matter systems. However, the optical access required for NV spin readout remains an important hurdle for operation in challenging environments such as millikelvin cryostats or biological systems. Here, we demonstrate a scanning-NV sensor consisting of a diamond nanobeam that is optically coupled to a tapered optical fiber. This nanobeam sensor combines a natural scanning-probe geometry with high-efficiency through-fiber optical excitation and readout of the NV spins. We demonstrate through-fiber optically interrogated electron spin resonance and proof-of-principle magnetometry operation by imaging spin waves in an yttrium-iron-garnet thin film. Our scanning-nanobeam sensor can be combined with nanophotonic structuring to control the light-matter interaction strength, and has potential for applications that benefit from all-fiber sensor access such as millikelvin systems.