This article proposed a microwave (MW) detection method by utilizing the effect of the dual MW on nitrogen-vacancy (NV) centers in diamond. We established a theoretical model of dual MW superposition and experimentally discovered the unusual peak in the optically detected magnetic resonance (ODMR) spectrum. The peak frequency and the full-width at half-maximum of the unusual peak, as well as fluorescence intensity in the nonresonant frequency range of the ODMR spectrum, were systematically analyzed to obtain the frequency and amplitude of the measured MW signals. The broadband MW detection was realized in a wide range of 2240–4512 MHz by utilizing the linear relation between the magnetic field and the resonant frequency in the Zeeman splitting. The experiments showed that the minimum detection power was up to 1$\mu$W. The proposed approach can greatly improve the practicability of detecting MW fields on chip surfaces by quantum engineering techniques.
This article proposed a microwave (MW) detection method by utilizing the effect of the dual MW on nitrogen-vacancy (NV) centers in diamond. We established a theoretical model of dual MW superposition and experimentally discovered the unusual peak in the optically detected magnetic resonance (ODMR) spectrum. The peak frequency and the full-width at half-maximum of the unusual peak, as well as fluorescence intensity in the nonresonant frequency range of the ODMR spectrum, were systematically analyzed to obtain the frequency and amplitude of the measured MW signals. The broadband MW detection was realized in a wide range of 2240–4512 MHz by utilizing the linear relation between the magnetic field and the resonant frequency in the Zeeman splitting. The experiments showed that the minimum detection power was up to 1μW. The proposed approach can greatly improve the practicability of detecting MW fields on chip surfaces by quantum engineering techniques.
The efficient and reliable detection of microwave signals is a key element of the breakthrough in new-generation communication technology. In this article, we proposed an approach for the simultaneous identification of multiple microwave signals in a continuous frequency range based on the spectral hole-burning effect of nitrogen-vacancy (NV) centers. The protocol combines the quantum wide-field imaging method with magnetic gradient means, breaking the narrowband and discrete detection limitations of conventional optically detected magnetic resonance (ODMR) techniques. The frequencies of multiple microwave signals can be accurately decoupled by locating the relevant gaps on resonance frequency curves. Meanwhile, the effects induced by fixed-frequency signals with different powers on the resonance frequency curves were systematically analyzed. The experimental results indicated that the system realized a multiple-frequency resolution of 1 MHz and a minimum detectable power of 1 mW over a continuous bandwidth of 313-MHz. This proposal is capable of real-time and simultaneous detection of multiple microwave signals, which remarkably improves the utilization efficiency of spectrum resources.
Using continuous wave optical detection magnetic resonance (ODMR), diamond nitrogen-vacancy (NV) center has been widely used in magnetic field measurement at the experimental stage. Microwave and laser power have significant influence on the sensitivity of magnetic field measurement. A set of confocal magnetic field detection system based on the ensemble of NV center is established. By adjusting the microwave and laser power, it is observed that the contrast and the full width at half maximum (FWHM) of the ODMR spectra change obviously. The experiment indicates that the contrast has a maximum value under the change of microwave and laser power, while the FWHM is mainly dominated by microwave power at low light intensity. Adjusting the microwave power to obtain an applicable FWHM, then reducing the laser power appropriately, the light narrowing phenomenon could be observed, and the operation above could improve the sensitivity of magnetic field measurement effectively.
High-resolution wide-spectrum measurement techniques have important applications in fields such as astronomy, wireless communication, and medical imaging. Nitrogen-vacancy (NV) center in diamond is well known for its high stability, high sensitivity, real-time monitoring, single-point detection, and suitability for long-term measurement, and has an outstanding choice for spectrum analyzers. Currently, spectrum analyzers based on NV centers as detectors can perform real-time spectrum analysis in the range of several tens of gigahertz, but their frequency resolution is limited to a MHz level. In this study, we construct a quantum diamond microwave spectrum imaging system by combining continuous wave-mixing techniques. According to the spin-related properties of the NV center in diamond, we implement optical pumping by 532 nm green laser light illuminating the diamond NV center. A spherical magnet is used to produce a magnetic field gradient along the direction of the diamond crystal. By adjusting the size and direction of the magnetic field gradient, spatial encoding of the resonance frequency of the NV center is achieved. The magnetic field gradient induces the Zeeman effect on the diamond surface at different positions, generating corresponding ODMR signals. Through accurate programming, we coordinate the frequency scanning step size of the microwave source with the camera exposure and image storage time, and synchronize them circularly according to the order of image acquisition. Ultimately, after algorithmic processing, we successfully obtain comprehensive spectrum data in a range from 900 MHz to 6.0 GHz. Within the measurable spectrum range, the system employs continuous wave-mixing, simultaneously applying resonant microwaves and slightly detuning auxiliary microwaves to effectively excite the NV center. This method triggers off microwave interference effects, disrupting the balance between laser-induced polarization and microwave-induced spontaneous relaxation. Specifically, microwave interference causes the phase and amplitude of the fluorescence signal to change, leading to the generation of alternating current fluorescence signals. This further enhances the response of the NV magnetometer to weak microwave signals. The method enables the system to achieve a frequency resolution of 1 Hz in the measurable spectrum range, and it can separately measure the frequency resolution of multiple frequency points with a frequency step size of 1 MHz. The research results indicate that the wide-spectrum measurement based on NV centers can achieve sub-hertz frequency resolution, providing robust technical support for future spectrum analysis and applications.
This article presents a method to simultaneously determine multiple microwave signals using the hole-burning effect based on nitrogen-vacancy (NV) centers in diamonds. Tracking the anomalous peaks caused by fixed-frequency microwave signals in the optically detected magnetic resonance spectrum, the frequencies under test can be detected with high precision and accuracy in real time. Meanwhile, the applicability of the scheme in detecting microwave signals of different power is evaluated systematically by adjusting the power of measured fixed-frequency microwave signals. In addition, the frequency resolution of the system is characterized by modulating the frequency of one of the microwave signals. The experiment results indicate that the frequency resolution is as small as 5 kHz and the recognition deviation is less than 0.40 kHz. The method will provide a new idea in the field of electromagnetic compatibility testing, radio signal processing, and Internet of Things Engineering.
The nitrogen-vacancy (NV) center in diamond has attracted considerable attention as a highly sensitive quantum sensor that can operate at room temperature. In particular, continuous-wave optically detected magnetic resonance (CW-ODMR) is promising for a wide range of applications because of its simplicity. However, conventional AC magnetic-field sensing schemes based on CW-ODMR suffer from a limited detection bandwidth: the detectable frequency is either fixed by intrinsic physical parameters of the NV center or, even when tunable, restricted to a narrow range of only a few MHz. Here, we propose a broadband AC magnetometry scheme based on CW-ODMR with NV centers using microwave-driven dressed states.Through theoretical analysis and numerical simulations, we show that the proposed scheme enables the detection of AC magnetic fields with frequencies up to the order of 100 MHz, which has been difficult to achieve using conventional CW-ODMR-based methods.
Microwave (MW) magnetometry utilizing nitrogen-vacancy (NV) centers in diamond offers a broad, tunable detection bandwidth enabled by the magnetic-field-dependent electron spin resonances (ESR) of the NV centers. In this work, we present and experimentally demonstrate two NV-based protocols for spectral analysis of amplitude-modulated (MW) signals. The first protocol employs the NV center as a bandpass filter and reconstructs frequency-domain information of MW signals by sweeping the MW carrier frequency. The second protocol achieves optical imaging of the MW spectrum using an NV-based quantum spectrum analyzer, wherein a magnetic field gradient spatially maps the ESR frequencies of the NV centers, enabling parallel detection of multiple spectral components over a wide instantaneous bandwidth. Both protocols show results that agree well with reference measurements from a classical spectrum analyzer. Our approaches extend the application of spin-based quantum sensors to the field of modern communications and can be adapted for other spin-based quantum sensors.