掺钕微球的受激辐射激光和自受激拉曼散射

采用溶胶-凝胶法在SiO_2微球表面覆盖上一薄层Nd~(3+)掺杂SiO_2,并经电极放电熔融后形成表面光滑的高Q值微球.采用锥光纤将808 nm的抽运激光耦合入钕离子掺杂的高Q值微球形成回廊模,激发产生了1080—1097 nm波段受激辐射激光.由于所产生的激光有足够高的功率密度,在高Q SiO_2微球中激发产生了波长为1120—1143 nm一级自受激拉曼散射激光.推导了锥光纤掺钕微球组合的自受激拉曼散射的输出功率和阈值公式.描述了输出激光的特性:阈值、输出功率、线宽、边模抑制比.     

光学微球腔的热光效应用于温度传感器研究

为研究光学微球腔的热光效应,采用1550nm波段可调谐激光器和宽带光源两种泵浦源,分别测量了二氧化硅、碲酸盐玻璃微球及其掺杂了稀土离子的微球在激励光功率、环境温度变化时其谐振峰波长的变化量,得到了二氧化硅微球激励功率灵敏度为32.4pm/mW,温度灵敏度为13.4pm/℃;铥离子的掺杂使激励功率灵敏度达到48.7pm/mW,温度灵敏度达到15.2pm/℃.相应的碲酸盐微球激励功率灵敏度为71.1pm/mW,温度灵敏度为0.0191nm/℃,比光纤光栅温度传感器的灵敏度10pm/℃大了将近1倍,若掺杂了稀土离子,则高1.1倍.本文研究对微腔在温度传感器方面的应用具有参考意义.     

曲面光学元件表面微缺陷透射式偏振检测

国内外近些年来,对于光学元件表面缺陷的检测技术越来越重视。由于光学元件表面质量的好坏会直接影响到光学系统的性能。文章主要针对曲面光学元件中球面和柱面光学元件表面微缺陷的检测问题,提出了一种基于光偏振特性的检测方法。利用光学元件表面缺陷与无缺陷区域之间透射光偏振态的差异,提高整幅图像中缺陷的对比度。首先基于光的偏振理论,利用偏振片获得偏振照明光,并采用共焦照明的方式获得同时对焦的曲面光学元件缺陷图像。其后,利用计算机对缺陷图像进行处理。结果表明采用光的偏振特性对曲面光学元件表面微缺陷的检测,能够获得高对比度、高分辨率的缺陷特征。此方法很好的提高了曲面光学元件表面微缺陷的检测准确度和检测效率,结果表明缺陷的检测准确率达到了95%。     

Production of 87Rb Bose-Einstein condensates in a hybrid trap

We report a rapid evaporative cooling method using a hybrid trap which is composed of a quadrupole magnetic trap and a one-beam optical dipole trap. It contains two kinds of evaporative coolings to reach the quantum degeneracy: initial radio-frequency (RF) enforced evaporative cooling in the quadrupole magnetic trap and further runaway evaporative cooling in the optical dipole trap. The hybrid trap does not require a very high power laser such as that in the traditional pure optical trap, but still has a deep trap depth and a large trap volume, and has better optical access than the normal magnetic trap like the quadrupole-Ioffe-configuration (QUIC) cloverleaf trap. A high trap frequency can be easily realized in the hybrid trap to enhance the elastic collision rate and shorten the evaporative cooling time. In our experiment, pure Bose-Einstein condensates (BECs) with about 1 × 105 atoms can be realized in 6 s evaporative cooling in the optical dipole trap.     

Effects of Atom-Atom Interaction on Localization and Adiabaticity of BEC in One-Dimensional Disorder Optical Lattice

We numerically simulate the dynamical behavior of BEC in one-dimensional incommensurable optical lattice by split-step Fourier method in a time-dependent one-dimensional Gross Pitaevskii equation. It is indicated that the atom-atom interaction will weaken the localization and broaden the wave function, and it will destroy the adiabaticity of the ramped loading process in both single lattice and incommensurate lattice due to the broadening effect. A band structure model can interpret the difference of the adiabatic condition with non-interacting BEC in these optical lattices.