Surface charges greatly affect the discharge/flashover development process across an insulator. The relationship between surface charge distribution on insulating materials and measurement data based on Pockels techni...Surface charges greatly affect the discharge/flashover development process across an insulator. The relationship between surface charge distribution on insulating materials and measurement data based on Pockels technique is discussed, and an improved algorithm is built to calculate the real surface charge density from original data. In this algorithm, two-dimensional Fourier transform technique and Wiener filter are employed to reduce the amount of numerical calculation and improve the stability of computation, Moreover, this algorithm considers not only the influence of sample＇s thickness and permittivity, but also the impact of charges at different positions. The achievement of this calibration algorithm is demonstrated in details. Compared with traditional algorithms, the improved one supplies a better solution in the calibration of surface charge distribution on different samples with different thickness.展开更多
The invention of the laser unleashed the potential of optical metrology,leading to numerous advancements in modern science and technology.This reliance on lasers,however,also introduces a bottleneck for precision opti...The invention of the laser unleashed the potential of optical metrology,leading to numerous advancements in modern science and technology.This reliance on lasers,however,also introduces a bottleneck for precision optical metrology,as it requires sophisticated photonic infrastructure for precise laser-wave control,leading to limited metrology performance and significant system complexity.Here,we take a key step toward overcoming this challenge by demonstrating a Pockels laser with multifunctional capabilities that elevate optical metrology to a new level.The chip-scale laser achieves a narrow intrinsic linewidth down to 167 Hz and a broad mode-hop-free tuning range up to 24 GHz.In particular,it delivers an unprecedented frequency chirping rate of up to 20 EHz/s and an exceptional modulation bandwidth exceeding 10 GHz,both of which are orders of magnitude greater than those of existing lasers.Leveraging this laser,we successfully achieve velocimetry at 40 m/s over a short distance of 0.4 m,and measurable velocities up to the first cosmic velocity at 1m away—a feat unattainable with conventional ranging approaches.At the same time,we achieve distance metrology with a ranging resolution of<2 cm.Furthermore,for the first time to our knowledge,we implement a dramatically simplified architecture for laser frequency stabilization by directly locking the laser to an external reference gas cell without requiring additional external light control.This approach enables long-term laser stability with a frequency fluctuation of only±6.5 MHz over 60 min.The demonstrated Pockels laser combines elegantly high laser coherence with ultrafast frequency reconfigurability and superior multifunctional capability.We envision its profound impact across diverse fields including communication,sensing,autonomous driving,quantum information processing,and beyond.展开更多
光学电压互感器(Optical Voltage Transducer,OVT)是重要的电力系统测量设备。在使用过程中,因碰撞、连接不稳定或温度变化等问题,会导致传感光路或内部锗酸铋(BGO)晶体发生微小偏移。当偏移为0.5°时,所引起的最大积分电压误差可达...光学电压互感器(Optical Voltage Transducer,OVT)是重要的电力系统测量设备。在使用过程中,因碰撞、连接不稳定或温度变化等问题,会导致传感光路或内部锗酸铋(BGO)晶体发生微小偏移。当偏移为0.5°时,所引起的最大积分电压误差可达0.1%,这对于0.2%的标准要求而言是不可接受的。为了减小偏移带来的误差,并改善BGO晶体内电场的均匀性,文中针对110 kV纵向调制型OVT提出了一种方解石介质分层和氮化铝包裹法,两端采用Φ10 mm×75 mm的方解石对BGO晶体进行分压,并覆盖一层0.5 mm厚的氮化铝来避免与SF6气体直接接触。该结构模型成功解决了其他方法无法解决的晶体或者光路偏移导致的积分电压误差问题。根据仿真结果可知,其偏移误差降低至0.008%以下,并且通过实验所得到图像的标准差提高了35%以上,光强的分布均匀性得到了提高。仿真和实验结果均表明,这种优化改进方案显著提升了OVT的性能和稳定性,为电力系统的精准测量提供了可靠保障。展开更多
基金supported in part by National Natural Science Foundation of China(Nos.50937004,50777051)
文摘Surface charges greatly affect the discharge/flashover development process across an insulator. The relationship between surface charge distribution on insulating materials and measurement data based on Pockels technique is discussed, and an improved algorithm is built to calculate the real surface charge density from original data. In this algorithm, two-dimensional Fourier transform technique and Wiener filter are employed to reduce the amount of numerical calculation and improve the stability of computation, Moreover, this algorithm considers not only the influence of sample＇s thickness and permittivity, but also the impact of charges at different positions. The achievement of this calibration algorithm is demonstrated in details. Compared with traditional algorithms, the improved one supplies a better solution in the calibration of surface charge distribution on different samples with different thickness.
基金supported in part by the Defense Advanced Research Projects Agency(DARPA)LUMOS program under Agreement No.HR001-20-2-0044,and the National Science Foundation(NSF)(OMA-2138174,ECCS-2231036,OSI-2329017)This work was performed in part at the Cornell NanoScale Facility,a member of the National Nanotechnology Coordinated Infrastructure(National Science Foundation,ECCS-1542081)+1 种基金at the Cornell Center for Materials Research(National Science Foundation,Grant No.DMR-1719875)in the UCSB Nanofabrication Facility,an open access laboratory.
文摘The invention of the laser unleashed the potential of optical metrology,leading to numerous advancements in modern science and technology.This reliance on lasers,however,also introduces a bottleneck for precision optical metrology,as it requires sophisticated photonic infrastructure for precise laser-wave control,leading to limited metrology performance and significant system complexity.Here,we take a key step toward overcoming this challenge by demonstrating a Pockels laser with multifunctional capabilities that elevate optical metrology to a new level.The chip-scale laser achieves a narrow intrinsic linewidth down to 167 Hz and a broad mode-hop-free tuning range up to 24 GHz.In particular,it delivers an unprecedented frequency chirping rate of up to 20 EHz/s and an exceptional modulation bandwidth exceeding 10 GHz,both of which are orders of magnitude greater than those of existing lasers.Leveraging this laser,we successfully achieve velocimetry at 40 m/s over a short distance of 0.4 m,and measurable velocities up to the first cosmic velocity at 1m away—a feat unattainable with conventional ranging approaches.At the same time,we achieve distance metrology with a ranging resolution of<2 cm.Furthermore,for the first time to our knowledge,we implement a dramatically simplified architecture for laser frequency stabilization by directly locking the laser to an external reference gas cell without requiring additional external light control.This approach enables long-term laser stability with a frequency fluctuation of only±6.5 MHz over 60 min.The demonstrated Pockels laser combines elegantly high laser coherence with ultrafast frequency reconfigurability and superior multifunctional capability.We envision its profound impact across diverse fields including communication,sensing,autonomous driving,quantum information processing,and beyond.
