[Paper Review] Millimeter-scale rigid diamond probe for high sensitivity endoscopic-magnetometry applications

Jihongbo Shen, Heng Yuan+7 more|arXiv (Cornell University)|Feb 4, 2026

Diamond and Carbon-based Materials Research0 citations

TL;DR

The paper demonstrates a millimeter-scale rigid diamond magnetometer probe that achieves 200 pT/Hz1/2 sensitivity by optimizing optical design, using a frustum diamond coupled to a mini CPC lens to boost fluorescence collection by 37% within a 4 mm diameter, aimed at endoscopic applications.

ABSTRACT

Magnetometry based on diamond nitrogen-vacancy (NV) centers has been extensively studied for applications requiring diverse capabilities, spanning from nanometer spatial resolution to subpicotesla sensitivity. Among various applications, diamond magnetometers can demonstrate high sensitivity magnetic sensing within millimeter-scale size for endoscopic applications. However, the trade-off between sensitivity and spatial resolution of diamond magnetometry makes it difficult to achieve such a probe. In this study, we present a millimeter-scale rigid diamond magnetometer probe with enhanced sensitivity via optimizing the optical design. By coupling the frustum diamond with the miniaturized compound parabolic concentrator (CPC) lens, we enhance the fluorescence collection efficiency by 37% within 4 mm diameter, and the achieved sensitivity is 200 pT/Hz1/2 based on the sample with the resonance linewidth of ~8 MHz. With this verified structure, endoscopes with mm-size probe and picotesla sensitivity can be projected for surgical and industrial applications in the future.

Motivation & Objective

• Motivate high-sensitivity magnetic sensing within millimeter-scale probes for endoscopic applications.
• Balance optical design to improve sensitivity without sacrificing spatial resolution.
• Demonstrate a rigid mm-scale diamond probe by optimizing fluorescence collection.
• Quantify sensitivity improvements and collection efficiency with a frustum diamond-CPC configuration.

Proposed method

• Couple a frustum diamond to a miniaturized compound parabolic concentrator (CPC) lens to boost fluorescence collection.
• Characterize fluorescence collection efficiency improvements (reported as 37% within 4 mm diameter).
• Measure magnetic resonance linewidth (~8 MHz) and infer magnetometer sensitivity (200 pT/Hz1/2).
• Validate the rigid mm-scale probe structure for potential integration with endoscopes.

Experimental results

Research questions

• RQ1 Can a millimeter-scale diamond magnetometer achieve high sensitivity suitable for endoscopic use?
• RQ2 How does optical design optimization, specifically frustum diamond coupling with CPC, affect fluorescence collection and overall sensitivity?
• RQ3 What are the achievable sensitivity and linewidth constraints for mm-scale NV-center-based magnetometers in endoscopic configurations?
• RQ4 Is the proposed probe geometry compatible with mm-scale endoscopes and future picotesla-level sensitivity?

Key findings

• Achieved 200 pT/Hz1/2 sensitivity with a resonance linewidth of ~8 MHz.
• Enhanced fluorescence collection efficiency by 37% within a 4 mm diameter via frustum diamond and CPC lens.
• Demonstrated a millimeter-scale rigid diamond magnetometer probe with improved optical design for potential endoscopic deployment.
• Suggests that endoscopes with mm-size probes could reach picotesla sensitivity in future work.
• Provides a verified structure as a step toward mm-scale endoscopic magnetometry applications.