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Other areas of optics|5 Article(s)
Diagnosis of Cold Plasma Electromagnetic Parameters Based on Defective Microwave Photonic Crystal
Yanjing Zhu, Yong Mei, and Shenyun Wang
Plasma electromagnetic parameters are very important in development of plasma technology. In this paper, a testing method is presented based on a one-dimensional microwave photonic crystal with the cold plasma under test as a defective layer. The transfer matrix method (TMM) is used to simulate the relationship among plasma parameters, frequency offset of the defective peak, and the peak transmission intensity. The results indicate that the plasma and collision frequencies can be mapped into the frequency offset of the defective peak and the peak transmission intensity. Therefore, one can obtain the plasma electromagnetic parameter frequency by measuring the offset of the defective peak and the peak transmission intensity. This measuring approach provides a noncontact and sensitive way of sensing the electromagnetic parameters of cold plasma. Plasma electromagnetic parameters are very important in development of plasma technology. In this paper, a testing method is presented based on a one-dimensional microwave photonic crystal with the cold plasma under test as a defective layer. The transfer matrix method (TMM) is used to simulate the relationship among plasma parameters, frequency offset of the defective peak, and the peak transmission intensity. The results indicate that the plasma and collision frequencies can be mapped into the frequency offset of the defective peak and the peak transmission intensity. Therefore, one can obtain the plasma electromagnetic parameter frequency by measuring the offset of the defective peak and the peak transmission intensity. This measuring approach provides a noncontact and sensitive way of sensing the electromagnetic parameters of cold plasma.
Laser & Optoelectronics Progress
- Publication Date: Mar. 10, 2022
- Vol. 59, Issue 5, 0535001 (2022)
Numerical Simulation of Plasma Generated by Laser-Assisted Pulsed Discharge in Water
Yang Qian, Yinqi Feng, Minshuang Huang, and Youwen Xu
A laser-assisted pulsed discharge method for generating plasma in water is proposed. Combining with the classical Drude model, a two-dimensional fluid mathematical model of the plasma generated by laser injected into the water pulsed discharge system is established, and the corresponding mathematical equations are given. The COMSOL Multiphysics software is used to simulate the interaction process between charged particles and laser vertically injected into the plasma channel, The local electron density when the laser with a certain energy is applied to the water dielectric pulse discharge system is studied. The preliminary simulation results show that the peak value of electron density increases from 1.65 × 1021 m-3 to 8.29 × 1021 m-3 when a laser with 50 mJ energy and 0.1 mm spot diameter is added into the plasma channel. This process plays a significant role in improving the ionization rate of plasma, which indicates that the technical scheme of laser assisted pulse discharge in water to generate plasma is feasible. A laser-assisted pulsed discharge method for generating plasma in water is proposed. Combining with the classical Drude model, a two-dimensional fluid mathematical model of the plasma generated by laser injected into the water pulsed discharge system is established, and the corresponding mathematical equations are given. The COMSOL Multiphysics software is used to simulate the interaction process between charged particles and laser vertically injected into the plasma channel, The local electron density when the laser with a certain energy is applied to the water dielectric pulse discharge system is studied. The preliminary simulation results show that the peak value of electron density increases from 1.65 × 1021 m-3 to 8.29 × 1021 m-3 when a laser with 50 mJ energy and 0.1 mm spot diameter is added into the plasma channel. This process plays a significant role in improving the ionization rate of plasma, which indicates that the technical scheme of laser assisted pulse discharge in water to generate plasma is feasible.
Laser & Optoelectronics Progress
- Publication Date: Jan. 01, 2021
- Vol. 58, Issue 7, 0735001 (2021)
Algorithm for Screening Navigation Stars on Star Sensors
Wang Haiyong, and Xu Hao
In order to reduce the capacity of the navigation star database, an algorithm for screening navigation stars on star sensors is proposed. Uniformly distributed optical random vectors on the celestial sphere are generated and used for the Monte Carlo samples. The bright stars in the circumferential field of view （FOV） determined by each optical axis vector are in turn taken as the star subsets. The stars not found in the constructing star database are added to the constructing database in these star subsets and simultaneously the duplicate stars are discarded. After traversing all the implementation samples, one can finally obtain the navigation star database. The simulation condition is set as follows. The FOV of the star sensor is 15°×15°, the limiting star magnitude is 5.6 m, the angular distance threshold between stars is 1°, and the number of navigation stars required for star map matching is 15. The navigation star database constructed by this algorithm improves the uniformity of the navigation star′s distributions. In the necessary and sufficient sense of star map matching, the number of navigation stars in the star database reach the minimum. It thus reduces the number of matching pattern databases and reduces the memory requirements, which shows the engineering and practical value for the design of star sensors. In order to reduce the capacity of the navigation star database, an algorithm for screening navigation stars on star sensors is proposed. Uniformly distributed optical random vectors on the celestial sphere are generated and used for the Monte Carlo samples. The bright stars in the circumferential field of view （FOV） determined by each optical axis vector are in turn taken as the star subsets. The stars not found in the constructing star database are added to the constructing database in these star subsets and simultaneously the duplicate stars are discarded. After traversing all the implementation samples, one can finally obtain the navigation star database. The simulation condition is set as follows. The FOV of the star sensor is 15°×15°, the limiting star magnitude is 5.6 m, the angular distance threshold between stars is 1°, and the number of navigation stars required for star map matching is 15. The navigation star database constructed by this algorithm improves the uniformity of the navigation star′s distributions. In the necessary and sufficient sense of star map matching, the number of navigation stars in the star database reach the minimum. It thus reduces the number of matching pattern databases and reduces the memory requirements, which shows the engineering and practical value for the design of star sensors.
Laser & Optoelectronics Progress
- Publication Date: Jan. 01, 2021
- Vol. 58, Issue 1, 135001 (2021)
Statistical Characteristic Law of Average Deviation of Solar Elevation in Different Regions
Xingqing Zhang, Fang Pang, Weiping Lu, and Mengxiang Tan
In order to grasp the accuracy of solar radiation data from earth system simulation and remote sensing ground object inversion, it is necessary to discuss the regional representation of solar elevation caused by scale effect and the method for determining the data density of solar elevation. The calculation method of average deviation of regional solar elevation is designed and the sample data with reasonable distribution is established. The average deviation of regional solar elevation is calculated with the sample data selected according to the calculation method. Its regular characteristics are summarized according to the established statistical method. According to the statistics, the average deviation of regional solar elevation is substantially correlated with the regional diameter, they are nearly linear relation of positive correlation, and the linear coefficient slightly decreases with the increase of the regional diameter. When the regional diameter is less than 3000 km, the deviation has positive linear relation with the regional diameter with the coefficient of (1.8969-1.9084)×10 -3 (°)·km -1. The dispersion degree of the average deviation of solar elevation in the region with the same width is very small. The results show that the statistical law is simple, with high stability and high reliability. The scientific evidence is provided for determining the data density of solar elevation in the regional or global earth system simulation and ground object inversion. In order to grasp the accuracy of solar radiation data from earth system simulation and remote sensing ground object inversion, it is necessary to discuss the regional representation of solar elevation caused by scale effect and the method for determining the data density of solar elevation. The calculation method of average deviation of regional solar elevation is designed and the sample data with reasonable distribution is established. The average deviation of regional solar elevation is calculated with the sample data selected according to the calculation method. Its regular characteristics are summarized according to the established statistical method. According to the statistics, the average deviation of regional solar elevation is substantially correlated with the regional diameter, they are nearly linear relation of positive correlation, and the linear coefficient slightly decreases with the increase of the regional diameter. When the regional diameter is less than 3000 km, the deviation has positive linear relation with the regional diameter with the coefficient of (1.8969-1.9084)×10 -3 (°)·km -1. The dispersion degree of the average deviation of solar elevation in the region with the same width is very small. The results show that the statistical law is simple, with high stability and high reliability. The scientific evidence is provided for determining the data density of solar elevation in the regional or global earth system simulation and ground object inversion.
Laser & Optoelectronics Progress
- Publication Date: Feb. 15, 2020
- Vol. 57, Issue 3, 033501 (2020)
Extraordinary Transmission of TE-Polarization through Periodic Arrays of Metallic Slits Covered with Dielectric Medium
Wang Yawei, Deng Xiaobin, Wang Lifeng, Liu Mingli, and Hang Guangcai
Subwavelength periodic structures have many specific properties different from the traditional structures. Based on these properties,new nano-photonics devices can be designed. Using finite difference time domain (FDTD) numerical simulation methods,abnormal transmission phenomenon under TE polarized light excitation is realized by adding dielectric coating in the subwavelength peridic metallic slits. By comparing effects of adding dielectric in different locations such as left or right surface of metal films and metallic slits for extraordinary transmission phenomenon,it is proved that dielectric coatings on the metal films can excite a surface wave which transmits in dielectric waveguides in the metal slits,and results in extraordinary transmission phenomenon. Subwavelength periodic structures have many specific properties different from the traditional structures. Based on these properties,new nano-photonics devices can be designed. Using finite difference time domain (FDTD) numerical simulation methods,abnormal transmission phenomenon under TE polarized light excitation is realized by adding dielectric coating in the subwavelength peridic metallic slits. By comparing effects of adding dielectric in different locations such as left or right surface of metal films and metallic slits for extraordinary transmission phenomenon,it is proved that dielectric coatings on the metal films can excite a surface wave which transmits in dielectric waveguides in the metal slits,and results in extraordinary transmission phenomenon.
Laser & Optoelectronics Progress
- Publication Date: Jun. 03, 2020
- Vol. 47, Issue 4, 43101 (2010)
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