研究目的
To develop an optical broadband sensor for high-resolution and minimally invasive imaging of radio frequency (RF) magnetic fields using a diamond crystal with nitrogen-vacancy (NV) centers.
研究成果
The proposed optical broadband diamond sensor enables high-resolution RF magnetic field imaging with micrometer spatial resolution and minimized invasiveness. It achieves a sensitivity of approximately 230 ppm/Gauss and a detection sensitivity of 10 μT, with a 3 dB bandwidth of 15 MHz. The sensor is suitable for applications in extreme conditions due to diamond's inert properties. Future improvements could focus on noise suppression and bandwidth enhancement.
研究不足
The minimum measurable amplitude is limited by the noise floor of the avalanche photodetector, currently on the order of 0.1 Gauss. The bandwidth is limited to 15 MHz due to the fluorescence rate of NV centers. Spatial resolution is currently 50 μm but could be improved with smaller diamonds. The method requires a dc bias magnetic field and is sensitive to optical noise.
1：Experimental Design and Method Selection:
The technique is based on the modulation of fluorescence from NV centers in diamond under green laser excitation by an off-axis magnetic field at radio frequencies. A static magnetic field is applied to bias the system, and the fluorescence intensity is linearly modulated by the RF magnetic field.
2：Sample Selection and Data Sources:
A 60 μm diamond crystal containing NV centers is used as the sensor probe. The device under test (DUT) includes a circular spiral planar antenna and a 7-turns round loop for generating RF magnetic fields.
3：List of Experimental Equipment and Materials:
Equipment includes a green laser (532 nm), dichroic mirror, microscope objective, avalanche photodiode (APD) detector, manual and motorized translation stages, UV curable glue, Thorlab NEL01 noise eater, acoustooptic modulator (AOM), adjustable aperture, Keysight N9010A signal analyzer, long pass filter, and permanent magnets. Materials include the diamond crystal and RF cables.
4：Experimental Procedures and Operational Workflow:
The diamond is attached to a fiber end and placed near the DUT. The laser excites the NV centers, and fluorescence is collected and detected. The DUT is scanned using motorized stages for field mapping. Optical noise reduction methods are applied, and signals are analyzed using the signal analyzer or lock-in techniques.
5：Data Analysis Methods:
Fluorescence modulation depth is measured and normalized. Magnetic field sensitivity and bandwidth are characterized using the Biot-Savart law for calibration and signal analysis tools for frequency response.
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