Yingpeng Zhao

The Cold Atom Interference Gyroscope (CAIG) offer substantial potential for rotation measurement due to the high sensitivity and stability. The CAIG with a fountain configuration realized by 4-pulse could provide a larger interference-loop area, and enhanced performance. However, this kind of CAIG is usually much larger and higher since it requires a vacuum chamber with sufficient height to achieve a long Raman pulse interval. We demonstrate a 4-pulse CAIG based on a miniaturized vacuum chamber that enables portable and transportable rotation rate measurements. The main vacuum chamber is realized by whole glass material. The height of the vacuum unit is 0.7 m, the volume is 8.86 × 10 ⁴ cm ³ and the mass is 75 kg. Then, we estimated the performance of our portable CAIG in the environment of the underground laboratory and the fifth-floor office building. In the laboratory, the sensitivities of the homemade CAIG is 4.44 × 10 ⁻⁶ rad/s/√Hz with an interrogation time of 55 ms and an interference area of 25 mm ² . In addition, we measured the angular velocity of the Earth, the relative error is 2.4%. Furthermore, we transported the CAIG to the fifth floor of the office building, which is near the subway. Ultimately, the CAIG achieved a sensitivity of 5.47 × 10 ⁻⁴ rad/s/√Hz. Additionally, the theoretical maximum interrogation time achieved by this CAIG is 124 ms corresponding to a sensitivity of 5.62 × 10 ⁻⁸ /√Hz. Our new design of the compact CAIG could provide novel insights into the miniaturization of CAIGs, while also pointing out areas for further improvement.

Marine gravity survey is of great significance to the fields of geophysics research, marine geological mapping, and so on. Usually, accuracy calibration is required since the gravity measurements remain relative at present. For this application, the absolute gravity reference point is necessary, which can be established with classical optical absolute gravimeters. In this paper, an absolute gravity benchmark is constructed through a gravity measurement system based on a homemade atomic gravimeter at the quay of Zhoushan Archipelago. Even in the rugged environment of seaboard, a measurement sensitivity of 0.76 mGal/√Hz is obtained. Besides, the estimated absolute accuracy of gravity is better than 30 μGal. Interestingly, it is found that the accuracy has been affected greatly by the ocean tidal loading (OTL) effect, especially the absence of an accurate OTL model in the observation region. In order to further investigate the OTL effect, the continuous absolute gravity observations are carried out for 7 days, collecting tidal heights as well. Notably, a peak-to-peak amplitude of approximately 170 μGal is obtained even when the gravity variations caused by solid tide effect have been corrected. However, the calculated values with the existing OTL models seem much smaller than the actual gravity variation data. To solve this problem, an optimized OTL model for offshore gravity measurement has been proposed through an analysis of the existing models. With the improved model of OTL, the calculated results agree well the experimental data. These findings offer valuable insights for the high-precision calibration of marine gravimeters.

The Earth’s gravity field is complex and variable. Performance evaluation of gravimeter requires gravity fields with well-known absolute gravity values. The aim of this study is to utilize an in-house developed Cold Atom Gravimeter (CAG-E) in conjunction with CG-5 to establish a comprehensive test field consisting of 13 gravity datums at different altitudes. This absolute gravity field can be used for testing multiple relative gravimeters at the same time. The additional theoretical model calculations of this test field can provide a reference for gravity values at different heights, and a three-dimensional test field can be constructed in the future. In addition, a detailed performance evaluation of CAG-E was performed where the accuracy of the instrument repeatability was found to be 4.8 μGal. Finally, a correction of the geological density of the mountain was carried out using the absolute gravity values, and a minimum gravity difference residual of 0.9 μGal was obtained. These results verify the reliability of this test field for relative gravimeters.

Laser diffraction (LD) has many obvious advantages for measuring. However, the measurement accuracy is limited by a number of factors, such as imaging noise, sensor threshold, and fitting methods. In this paper, we present a novel method for measuring filament diameter based on image-based fitting, which maintains more information. Before fitting the diffraction image, image processing is applied to solve the problem of image noise and the non-linear response of the charge-coupled device (CCD). Then, a fitting formula is established based on the distribution of laser intensity on a diffraction image, and the fitted results are solved with the Levenberg–Marquardt (LM) algorithm. Finally, the initial parameters of a fit are obtained by calculation, which speeds up the calculation and improves the accuracy of the fitting. The measurement accuracy of this method is verified by experimental and theoretical analysis. In experiments, the filament diameters of 125 and 125.2 μm are measured with a relative error of approximately 0.12%, Furthermore, the superiority of this method is demonstrated by comparing the measurements with other methods. To verify the stability of the measurements, filament diameters of 110–180 μm are chosen to be measured with a relative standard deviation of less than 0.14%.

In this paper, a compact laser system for ⁸⁷Rb atom interferometry based on only one free-space electro-optic modulator (EOM) was realized, where repumping and Raman beams were generated with a free-space EOM. In addition, this laser system does not require a laser amplifier compared to fibered EOM since fibered EOM cannot transmit high-power lasers. However, due to the narrow modulation linewidth of free-space EOM, it is impossible to obtain the frequencies of repumping and Raman beams separately, which would lead to some complicated effects. Therefore, a theoretical analysis was carried out to solve this problem, and a new frequency scheme for AI is proposed. For the experiment, the laser system of AI was built up. Moreover, the atomic interference fringes were obtained with a contrast of 20.7% (T = 60 ms) and the fitted phase resolution is approximately 1.25 mrad. The presented laser system could provide a new solution for compact AI systems in the future.