Beijing Zhenxing Metrology & Measurement Institute

Abstract Tapered lasers are extensively employed in high power single-mode lasing, yet still suffering from the potential formation of higher-order transverse modes in the tapered region, which severely degrades the laser beam quality. Herein, we propose a novel supersymmetric segmented tapered laser to achieve stable fundamental transverse mode operation. Our design features a three-segmented tapered waveguide along the light propagation direction, with sub-waveguides of varying widths flanking each main waveguide segment. The main waveguides measure 8 μm, 12 μm, and 16 μm in width. Specifically, the 8 μm main waveguide has a corresponding subsidiary waveguide of 2.67 μm; the 12 μm main waveguide has two subsidiary waveguides measuring 4.82 μm and 6.63 μm; and the 16 μm main waveguide has two subsidiary waveguides measuring 7.13 μm and 3.68 μm. Based on coupled-mode theory, we systematically analyzed the coupling coefficients under different inter-waveguide spacings, leading to an optimized spacing of 1.2 μm through comprehensive theoretical simulations and fabrication compatibility constraints. Furthermore, phase-shifted gratings were integrated between tapered waveguide segments to enable precise longitudinal mode selection. This synergistic design could successfully realize robust single-mode operation, offering a scalable framework for on-chip integrated high-power, high-beam-quality tapered lasers.

Spin-based quantum sensors have been applied to the quantum sensing of magnetic fields from DC to GHz with various schemes. The recently developed quantum spectrum analyzer (QSA) technique based on the nitrogen-vacancy (NV) centers in diamond shows an ultrawide frequency bandwidth in this application. Here, we improve this technique and develop a robust QSA via diamond engineering. This QSA exploits the electron spin resonance of NV centers in an engineered {111} industrial diamond, which cancels the complex process of magnetic arrangement and significantly enhances the robustness of QSA against spin mixing under high magnetic fields in practice. A tunable frequency bandwidth of up to 18 GHz with a maximum instantaneous bandwidth of 2 GHz is achieved as well as a frequency resolution of several MHz and a large dynamic range of 65 dB. Using this QSA, we realize the optical imaging of frequency-modulated microwaves. Our work provides a promising rapid-deployment architecture for QSA and extends its application to spectral analysis in modern communications.

As Synthetic Aperture Radar (SAR) now plays a significant role in the military, developing effective SAR jamming techniques has become a critical challenge. With the aim of addressing the poor adaptive capability of traditional jamming methods, this paper proposes a dynamic SAR jamming strategy selection technique based on signal feature analysis and a Convolutional Neural Network. This method transforms the jamming strategy selection problem into a pattern recognition problem for SAR imaging results, enabling the adaptive adjustment of jamming. A jamming effect evaluation model is constructed, and simulation results verify the effectiveness and adaptability of the proposed method.

In strong smoke-scattering environments, single-photon counting lidar faces the dual challenges of intense scattering noise and low echo photon counts, which result in extremely low signal-to-noise ratios (SNRs) and consequently severely limited smoke-penetrating imaging performance. The residual noise photons persist after the Gamma model fitting of the backscattering peak in smoke environments and interfere with the accuracy of the target Gaussian model fitting. To address this issue, this work proposed a smoke-penetrating 3D imaging algorithm based on DBSCAN residual clustering-guided Gaussian model fitting. First, a Gamma model was constructed to fit the echo photon data, provide an initial estimate of the target echo position, and separate the backscattering peak. Then, a DBSCAN density clustering algorithm was designed to analyze the fitting residuals and effectively identify and remove residual noise photons to precisely isolate the target signal peak. Finally, Gaussian model fitting was performed on the filtered target photons to achieve high-precision depth estimation. The proposed method effectively separates the signals from noise in smoke-scattering environments using DBSCAN density clustering. Experimental results on the Middlebury simulation dataset show that the proposed algorithm achieved lower root mean square error (RMSE) and higher structural similarity (SSIM) in both the Art and Bowling scenes across varying smoke particle sizes (0.4,1,10 and 20 µm) compared to conventional algorithms. Furthermore, real-world outdoor experiments under rainy and foggy conditions further confirmed its reconstruction capability. These improvements significantly enhanced the quality and accuracy of imaging in smoke-scattering environments.

Compared with the conventional three-dimensional magneto-optical trap (3D MOT), the grating magneto-optical trap (GMOT) enables the cooling and trapping of atoms with only a single beam of light, thereby significantly reducing the overall volume of the device. Here, a grating chip with high diffraction efficiency is designed, and its parameters are optimized through simulations, which effectively suppresses the power of the zero-order diffracted light. Subsequently, the grating chip is fabricated and characterized, and using this chip, we successfully trap 1.7×10⁶ atoms. The temperatures of the atomic cloud in the axial and radial directions are 5.6 mK and 17.0 mK, respectively. The successful implementation of the atom cooling and trapping experiment based on the diffraction grating provides important reference for the miniaturization of cold atom-based quantum sensors.

In this paper, a method for measuring the pose of roadheader is proposed, which using a laser beam and a multi-vision target. The multi-vision target consists of cameras, a biaxial inclinometer and a target screen. By sensing the gravity and light vector in the roadway, the pose of the roadheader relative to the roadway navigation coordinate frame can be obtained. The experiment was conducted in a closed dark channel simulating the environment of a coal mine tunnel, The multi-view target was positioned 100 meters away from the laser emission source. After repeated measurements at a sampling frequency of 30 Hz, the measurement precision of pose angle is better than 0.0683°, and the position measurement accuracy is better than 11 mm. All measurement functions involved in the method are realized inside the multi-vision target without changing the environment of coal mine roadway. Therefore, this method has strong on-site adaptability and can meet the requirements of pose measurement for roadheader.

This paper introduces an air-bearing spiral loading Rockwell hardness standard machine that employs advanced air bearing technology to reduce the frictional force during spindle operation. This not only extends the spindle’s lifespan but also significantly reduces the measurement error caused by test force, solving the problem of impact on hardness testing results due to spindle friction. The machine also features an independently designed spiral mass grading loading structure that, with different rotation angles, selects corresponding load masses for automatic scale load selection. A host computer, along with Siemens PLC, is used to complete the system control of the entire hardness standard machine, realizing self-adjusting detection processes. Field tests have shown that the precision of this air-bearing spiral loading Rockwell hardness standard machine is high, with stable performance and ease of use, meeting the requirements of value transfer and traceability.