National Institute of Metrology

Abstract Ultranarrow linewidth fiber lasers have good application prospects in high-precision spontaneous Raman detection systems due to their excellent frequency stability and low phase noise characteristics. This study first presents a theoretical derivation of the influence between laser linewidth and Raman detection performance, focusing on signal-to-noise ratio. Subsequently, a self-developed ultranarrow linewidth fiber laser, featuring a linewidth of 650 Hz, is utilized to experimentally validate the influence of laser linewidth on signal-to-noise ratio. The results demonstrate that reducing the laser linewidth from 200 kHz to 650 Hz improves the signal-to-noise ratio of mid frequency spectra by a factor of 1.58. This work offers both a theoretical foundation and experimental evidence to support the optimization of Raman system design.

Abstract Lead halide perovskites have received widespread attention in the field of optoelectronics due to their high photoluminescent efficiency, tunable bandgap, and excellent color purity. However, the inherent toxicity and instability of lead significantly limit its practical applications. In an effort to resolve these concerns, we have developed a lead-free alternative by embedding Eu 3+ -doped CsMnBr 3 quantum dots (QDs) into a borosilicate glass matrix. The resulting materials exhibit intense red luminescence under ultraviolet excitation, and Eu 3+ doping enhances the photoluminescence quantum yield by a factor of 3.37 through effective excitation energy migration from Mn 2+ to Eu 3+ ions. Benefiting from glass encapsulation, the composites show remarkable thermal stability and water resistance, retaining their optical properties for more than 450 d. Furthermore, prototype light-emitting diodes fabricated with the doped glass powders demonstrate strong red emission and comparable red-light penetration to commercial phosphor-based devices. These findings highlight the excellent operational stability and practical potential of Eu 3+ -doped CsMnBr 3 glass QDs for applications in anticounterfeiting, solid-state lighting, and other optoelectronic technologies.

To enhance the accuracy of wind shear identification by coherent Doppler wind lidar (CDWL), it is necessary to clarify the variation characteristics of CDWL detection results under typical airflow disturbance conditions. This study first numerically simulated typical wind shear fields and generated the Plane Position Indication (PPI) results of CDWL through coordinate projection. Then, it compared the performance of the double-slope algorithm and the least squares algorithm on wind shear identification from the PPI data. The results showed that for wind fields with significant peak characteristics, the double-slope algorithm can more sensitively identify wind shear near the peak, compared with the least square algorithm. In contrast, for wind fields with stable, continuous and linear gradient characteristics, the least squares algorithm can better suppress noise and fit the wind speed gradient changes. Finally, a self-developed long-range CDWL was used to conduct wind shear detection experiments at a plateau airport. After the CDWL beam position was calibrated, its data were compared with those from the anemometer. The "least square + double-slope" scheme was adopted to analyze the typical wind shear case, and the effectiveness and reliability of the identification scheme were verified in combination with an aircraft crew report.