Robust 1-μm-Resolution Magnetic Probe Enabled by Optical Trapping of Nanodiamonds on a Tapered Fiber.

Fang, Die; Wang, Yibo; Wang, Xin; Gao, Yaoguo; Zhang, Zhengfei; Liu, Mengjia; Wang, Shuo; Xu, Feng et al. · Nano Lett · 2025

basic_science · Level V

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Abstract

High-resolution magnetic field scanning is critical for investigating nanoscale spin systems and characterizing defects in microelectronic devices. We present a fabrication-free approach to create robust magnetic probes with 1-μm spatial resolution by synergizing the quantum magnetic sensitivity of nitrogen-vacancy (NV) centers in nanodiamonds with the enhanced photon efficiency of tapered fibers. Through gradient-force optical trapping, nanodiamonds are precisely positioned at the fiber tip, where van der Waals forces immobilize them without requiring micro-nanoprocessing. In addition to possessing high spatial resolution, the probe exhibits a magnetic sensitivity reaching <math xmlns="http://www.w3.org/1998/Math/MathML"><mn>80</mn><mo>⁡</mo><mi>μ</mi><mi>T</mi><mo>/</mo><msqrt><mrow><mi>Hz</mi></mrow></msqrt></math>. By demonstrating a magnetic field scan of crossed microwires, this method can be extended to measure tiny magnetic structures or microcircuits, leveraging the integrated photonic enhancement of tapered fibers for robust high signal-to-noise sensing.