Towards high spatial resolution magnetic imaging with a compact practical quantum diamond microscope

TL;DR

This paper introduces a practical quantum diamond microscope with a novel sensor holder design that achieves high spatial resolution below 500 nm, balancing ease of use and optical performance.

Contribution

The authors present a new co-axial sensor holder enabling high-resolution magnetic imaging with a compact diamond microscope, simplifying sensor-sample interfacing.

Findings

Achieved <500 nm spatial resolution with a millimeter-sized sensor.

Demonstrated the relationship between spatial resolution and optical NA.

Identified optical aberrations affecting high NA resolution.

Abstract

Widefield quantum diamond microscopy is a powerful technique for imaging magnetic fields with high sensitivity and spatial resolution. However, current methods to approach the ultimate spatial resolution ($<500\,$nm) are impractical for routine use as they require time-consuming fabrication or transfer techniques to precisely interface the diamond sensor with the sample to be imaged. To address this challenge, we have designed a co-axial sensor holder that enables simple, repeatable sensor-sample interfacing while being compatible with high numerical aperture (NA) optics. With our new design we demonstrate low standoffs $<500\,$nm with a millimetre sized sensor. We also explore the relationship between spatial resolution and NA spanning from 0.13 to 1.3. The spatial resolution shows good agreement with the optical diffraction limit at low NA but deviates at high NA, which is shown to be due to optical aberrations. Future improvements to our design are discussed, which should enable magnetic imaging with $<500\,$nm resolution in an accessible, easy-to-use instrument.