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Quantum sensing based on nitrogen-vacancy centers in diamond has shown excellent properties. Combined with the imaging technique, it shows exciting practicability. Here, we demonstrate the simultaneously imaging technique of magnetic field and temperature using a wide-field quantum diamond microscope. We describe the operating principles of the diamond microscope and report its sensitivity (magnetic field ${\sim}1.8~\mu \mbox{T/Hz}^{1/2}$ ∼ 1.8 μ T/Hz 1 / 2 and temperature ${\sim}0.4~\mbox{K/Hz}^{1/2}$ ∼ 0.4 K/Hz 1 / 2 ), spatial resolution (1.3 μm), and field of view ($400 \times 300~\mu \mbox{m}^{2}$ 400 × 300 μ m 2 ). Finally, we use the microscope to obtain images of an integrated cell heater and a PCB, demonstrating its ability in the application of magnetic field and temperature simultaneously imaging at wide-field.

We demonstrate a method for thermal detection that is the sensitivity 6.2 mK Hz−1 2, which uses the frequency lock closed-loop scheme to track Zeeman-split resonance of nitrogen-vacancy (NV) centers in diamond. The NV diamond surface acts as a temperature measurement sensor to transfer the temperature variation as D(T) parameter change to lead to the movement of the energy levels to detect the temperature. By frequency modulation technology and closed-loop feedback locking technology, automatic temperature detection and step signal reading are realized, with a resolution of 7.6 mK. It is found that the closed-loop output is basically unchanged, while the open-loop output has an error signal proportional to the laser fluctuation. The closed-loop feedback technique can improve the stability and resolution of the system and provides a method for measuring the actual temperature detection. Such a demonstration marks a vital advance in transitioning the NV thermometer from a laboratory system to a functional device for detecting temperature fields in a practical environment.

We demonstrate a three-axis vector magnetometer based on ensembles of negatively charged nitrogen vacancy centers in single-crystal diamond. A diamond with $\text{C}_{3v}$ symmetry was used to establish the coordinate system for vector magnetic field sensing. We control the external static magnetic field with three-axis Helmholtz coils. Four pairs of magnetic resonance peaks were obtained, which were used to calculate the three Cartesian components of the magnetic field with sensitivity of $\sim5\;\text{nT}/ \sqrt{\text{Hz}}$ for each Cartesian component, free of interaxis error. The magnetometer is suitable for single-chip manufacturing.

A method for enhancement of the sensitivity of a spin sensor based on an ensemble of nitrogen vacancy (NV) color centers was demonstrated. Gold nanoparticles (NPs) were deposited on the bulk diamond, which had NV centers distributed on its surface. The experimental results demonstrate that, when using this simple method, plasmon enhancement of the deposited gold NPs produces an improvement of ∼10 times in the quantum efficiency and has also improved the signal-to-noise ratio by approximately ∼2.5 times. It was also shown that more electrons participated in the spin sensing process, leading to an improvement in the sensitivity of approximately seven times; this has been proved by Rabi oscillation and optical detection of magnetic resonance (ODMR) measurements. The proposed method has proved to be a more efficient way to design an ensemble of NV centers-based sensors; because the result increases in the number of NV centers, the quantum efficiency and the contrast ratio could greatly increase the device’s sensitivity.

For quantum sensing based on nitrogen-vacancy (NV) centers in diamond, microwave irradiation with uniform power density and large detection volume is necessary to achieve ultrahigh sensitivity. We demonstrate the fabrication of a double magnetic ring stereoscopic antenna used for the tridimensional uniform control of NV spin ensembles with a 4π mm2 × 2 mm large volume. Compared with those of traditional microwave antennas (copper wire and single-loop antenna), the sensitivity of the sensor can be improved 4.93 and 9.98 times, and the linearity of the lock-in signal can be increased by 2.04 and 1.11%, respectively. Moreover, the proposed antenna can suppress the thermal noise generated by itself and is amenable to three-dimensional (3D) integration.

Sensing properties of nitrogen (N)-riched diamond as the core component of the sensors based on ensemble nitrogen vacancy (NV) color centers has direct impact on sensors' performance. The concentration of paramagnetic centers (mainly NV−, NV0, and N) in N-riched diamond plays a decisive role in diamond sensing properties. Here, we proposed a method to evaluate sensing properties of N-riched diamonds as the sensor sensitive unit by associating parameters R (contrast) and (inhomogeneous spin relaxation time) in the ideal sensing model with concentrations of paramagnetic centers. The results can be used to design high sensitivity solid-spin-based sensors and explore the novel spin functional materials.

A novel method is proposed to improve the scale factor of the resonant fiber optical gyroscope. By using erbium-doped fiber splicing into the fiber ring resonator, forming active resonator to increase the depth of transmission.

Using linear approximation method, we calculate the intensity correlation time of a single-mode laser driven by both colored pump noise with signal modulation and quantum noise with cross-correlation between its real and imaginary parts, and analyze the influence of the signal, noise and its cross-correlation form on the statistical fluctuation of the laser system. We detect that the "color" of pump noise is an important factor that affects the statistical fluctuation of the laser system. When the colored pump noise is short time correlation, within a determinate parameter range, the intensity correlation time can be prolonged, and the statistical fluctuation of the laser system can be restrained by increasing the amplitude of modulation signal. The specific frequency of input signal will result in intensity correlation time to appear maximum, and the statistical fluctuation of the laser system is least here. When the colored pump noise is long time correlation, within a determinate parameter range, the intensity correlation time can be also prolonged by increasing the frequency of modulation signal and decreasing its amplitude, and the statistical fluctuation of the laser system will decrease. In particular, when the intensity of quantum noise increases and the cross-correlation between its real and imaginary parts enhance, the intensity correlation time will prolong, and the statistical fluctuation of the laser system is restrained.

The resonant microsphere gyroscope is proposed based on a double Faraday rotator system for the resonant microsphere gyroscope (RMSG) that is characterized by low insertion losses and does not destroy the reciprocity of the gyroscope system. Use of the echo suppression structure and the orthogonal polarization method can effectively inhibit both the backscattering noise and the polarization error, and reduce them below the system sensitivity limit. The resonance asymmetry rate dropped from 34.2% to 2.9% after optimization of the backscattering noise and the polarization noise, which greatly improved the bias stability and the scale factor linearity of the proposed system. Additionally, based on the optimum parameters for the double Faraday rotator system, a bias stability of 0.04°/s has been established for an integration time of 10 s in 1000 s in a resonator microsphere gyroscope using a microsphere resonator with a diameter of 1 mm and a Q of 7.2×10sup6/sup.