中国物理学会80年

1932年8月，中国物理学会成立了．至今，它走过了整整80年．这80年是不平坦的80年，在经历了艰难发展时期和曲折发展时期之后，它进入了蓬勃发展时期．     

Competition between Radiative Power and Dissipation Power in the Refrigeration Process in Oxide Multifilms

The maximum refrigeration power dependence on the doping density in the p-BaTiO3/BaTiO3/SrTiO3/BaTiO3/ n-BaTiO3 system and in the p-AlGaAs/AlGaAs/GaAs/AlGaAs/n-AlGaAs system is obtained respectively based on the opto-thermionic refrigeration model. The results show that the maximum refrigeration power in the p-BaTiO3/BaTiO3/SrTiO3/BaTiO3/n-BaTiO3 system increases dramatically with the increase of doping density from 1.0×1018 cm-3 to 5.0×1019 cm-3 while that in the p-AlGaAs/AlGaAs/GaAs/AlGaAs/n-AlGaAs system is nearly a constant. It is found that the different Auger coefficients and the competition between radiative power and dissipation power lead to the different behavior of the maximum refrigeration power dependence on the doping density of the two systems.     

集成微光机电系统中的矢量光学问题

集成微光机电(MOEM) 系统是近年来迅速地发展起来的一门新兴的综合学科,它融合了微光学元件、微电子器件和微机械结构的优点.不但在技术上有重要的应用,还蕴涵着与小尺寸器件有关的力学、热学、电学、光学,以及材料科学等丰富的基础科学研究课题.文章探讨了MOEM 系统中典型的微光学元件,如衍射微透镜、折射微透镜和微光栅中的矢量光学问题,简要地介绍了相应的求解方法.     

激光分子束外延氧化物薄膜机理研究

实验结果表明外延结构复杂的氧化物薄膜,基片温度在600～650℃条件下,其表面原胞层的扩散时间是几十秒到上百秒.根据此特点,采用单原胞间歇式外延,用激光分子束外延制备原子尺度控制的高质量氧化物薄膜和超晶格材料.     

用衍射相位元件分离并聚焦偏振光

通过相位恢复的原理,设计了在平行光的照明下单轴双折射晶体做成的衍射相位元件以实现分离并聚焦ｏ偏振光和ｅ偏振光,讨论了相位量化对结果的影响。理论计算表明：这种方法可成功地实现偏振光的分离和聚焦。     

Ultraviolet photovoltaic characteristic of MgB2 thin film

Fast photoelectric effects have been observed in MgB₂ thin film fabricated by chemical vapour deposition. The rise time was $\sim $10 ns and the full width at half-maximum was \sim185\,ns for the photovoltaic pulse when the film was irradiated by a 308\,nm laser pulse of 25\,ns in duration. X-ray diffraction and the scanning electron microscope revealed that the film was polycrystalline with preferred c-axis orientation. We propose that nonequilibrium electron--hole pairs are excited in the grains and grain boundary regions for MgB₂ film under ultraviolet laser and then the built-in electric field near the grain boundaries separates carriers, which lead to the appearance of an instant photovoltage.     

LASER MOLECULAR BEAM EPITAXY SYSTEM AND ITS KEY TECHNOLOGIES

The laser molecular beam epitaxy system and its key technologies have been successfully developed in China. Atomically regulated unit-cell by unit-cell homoepitaxial SrTiO₃ (STO) and heteroepitaxial BaTiO₃ (BTO) films and STO/BTO superlattices were fabricated on STO (100) substrates by the laser molecular beam epitaxy. The fine streak patterns and more than 1000 cycles of undamping intensity oscillation were obtained by using in-situ reflection high-energy electron diffraction. The surfaces of films are atomically smooth.     

CRYSTALLIZATION OF DIELECTRIC SPHERES IN LASER STANDING WAVE FIELD

Experimental study on crystallization of polystyrene spheres and SrTiO₃ particles in laser standing wave field is presented. The diameter of polystyrene, which are able to be trapped, is 7 times smaller than that reported by Burns, the corresponding lattice constant is reduced to 1.5 μm. The crystallization effect of SrTiO₃ particles with a refractive coastant of 2.5 in the visible range is observed for the first time. Based on the results above we believe that it is possible to construct photonic crystal with lattice constant extended to visible wave range by this method.     

原子尺度控制钙钛矿氧化物薄膜的异质外延生长和特性研究

用激光分子束外延,原子尺度控制的外延生长出多种钙钛矿氧化物异质结.X射线衍射和原子力显微镜测量结果表明,在Si基底上生长的SrTiO3和LaAlO3薄膜具有很好的外延结构和取向,其表面达到原子尺度的光滑.YBCO/SrNb0.01Ti0.99O3、La0.9Sr0.1MnO3/SrNb0.01Ti0.99O3(LSMO/SNTO)等异质结,均观测到较好的p-n结I-V特性.首次观测到钙钛矿结构氧化物p-n结电流的磁调制和正巨磁电阻效应,在255K条件下,当外加磁场分别为5×10-4T、1×10-3T、1×10-2T和0.1T时,LSMO/SNTO p-n结的磁电阻变化率ΔR/R0达到:46.7%、59.7%、70.5%和83.4%;当外加磁场为3T时,在100K条件下,在LSMO/SNTO多层p-n异质结上观测465%的正磁电阻变化率.     

悼念我的恩师——胡宁先生

 胡宁先生去世了,我国理论物理学界失去了一位杰出的前辈.我失去了一位尊敬的师长.胡先生的音容笑貌宛在,他的治学精神、扶掖后人的高贵品质,令人终生难忘.五六十年代,我求学于北京大学.