We study the dynamical evolution of cold atoms in crossed optical dipole trap theoretically and experimentally. The atomic transport process is accompanied by two competitive kinds of physical mechanics, atomic loadin...We study the dynamical evolution of cold atoms in crossed optical dipole trap theoretically and experimentally. The atomic transport process is accompanied by two competitive kinds of physical mechanics, atomic loading and atomic loss.The loading process normally is negligible in the evaporative cooling experiment on the ground, while it is significant in preparation of ultra-cold atoms in the space station. Normally, the atomic loading process is much weaker than the atomic loss process, and the atomic number in the central region of the trap decreases monotonically, as reported in previous research. However, when the atomic loading process is comparable to the atomic loss process, the atomic number in the central region of the trap will initially increase to a maximum value and then slowly decrease, and we have observed the phenomenon first. The increase of atomic number in the central region of the trap shows the presence of the loading process, and this will be significant especially under microgravity conditions. We build a theoretical model to analyze the competitive relationship, which coincides with the experimental results well. Furthermore, we have also given the predicted evolutionary behaviors under different conditions. This research provides a solid foundation for further understanding of the atomic transport process in traps. The analysis of loading process is of significant importance for preparation of ultra-cold atoms in a crossed optical dipole trap under microgravity conditions.展开更多
Circular-polarization discrimination appears in many antennas＇ applications. A compensation approach based on multilayer film structure is proposed to improve the axial ratio of the magnitude of the two perpendicular...Circular-polarization discrimination appears in many antennas＇ applications. A compensation approach based on multilayer film structure is proposed to improve the axial ratio of the magnitude of the two perpendicular modes of the lump ports. The goal is to widen the beamwidth of radiation that has an axial ratio less than 3 dB and thus reducing the complexity at the receiver. A transfer matrix method was developed to represent the multilayer film and characterize its performance. Simulation using high frequency structure simulator shows that a crossed dipole, as an example, can achieve a beamwidth of more than 30° at the frequency of 12.45 GHz after compensation. Finally, conclusions and future work about this compensation method are presented.展开更多
基金Project supported by the National Natural Science Foundation of China(Grant Nos.92365208,11934002,and 11920101004)the National Key Research and Development Program of China(Grant Nos.2021YFA0718300 and 2021YFA1400900)+1 种基金the Science and Technology Major Project of Shanxi(Grant No.202101030201022)the Space Application System of China Manned Space Program。
文摘We study the dynamical evolution of cold atoms in crossed optical dipole trap theoretically and experimentally. The atomic transport process is accompanied by two competitive kinds of physical mechanics, atomic loading and atomic loss.The loading process normally is negligible in the evaporative cooling experiment on the ground, while it is significant in preparation of ultra-cold atoms in the space station. Normally, the atomic loading process is much weaker than the atomic loss process, and the atomic number in the central region of the trap decreases monotonically, as reported in previous research. However, when the atomic loading process is comparable to the atomic loss process, the atomic number in the central region of the trap will initially increase to a maximum value and then slowly decrease, and we have observed the phenomenon first. The increase of atomic number in the central region of the trap shows the presence of the loading process, and this will be significant especially under microgravity conditions. We build a theoretical model to analyze the competitive relationship, which coincides with the experimental results well. Furthermore, we have also given the predicted evolutionary behaviors under different conditions. This research provides a solid foundation for further understanding of the atomic transport process in traps. The analysis of loading process is of significant importance for preparation of ultra-cold atoms in a crossed optical dipole trap under microgravity conditions.
基金supported by the Hi-Tech Research and Development Program of China(2006AA01Z246)the National Natural Science Foundation of China(60702005)
文摘Circular-polarization discrimination appears in many antennas＇ applications. A compensation approach based on multilayer film structure is proposed to improve the axial ratio of the magnitude of the two perpendicular modes of the lump ports. The goal is to widen the beamwidth of radiation that has an axial ratio less than 3 dB and thus reducing the complexity at the receiver. A transfer matrix method was developed to represent the multilayer film and characterize its performance. Simulation using high frequency structure simulator shows that a crossed dipole, as an example, can achieve a beamwidth of more than 30° at the frequency of 12.45 GHz after compensation. Finally, conclusions and future work about this compensation method are presented.
