Table of contents

20 January 1996, Volume 5 Issue 1 Previous issue    Next issue

GENERAL

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DETERMINATION OF CAPTURE BARRIERS OF DEFECTS FOR GaAs ALLOYS AND TRANSIENT PHOTO-RESISTIVITY SPECTROSCOPY WANG HAI-LONG (王海龙), FENG SONG-LIN (封松林), ZHOU JIE (周洁), YANG XI-ZHEN (杨锡震) Acta Physica Sinica (Overseas Edition), 1996, 5 (1):  1-9.  DOI: 10.1088/1004-423X/5/1/001 Abstract ( 1236 )   PDF (229KB) ( 430 )   Si-doped Ga0.7Al0.3As grown by molecular beam epitaxy (MBE) and undoped Ga0.47Al0.53As grown by chemical beam epitaxy (CBE) have been investigated using a new deep level characterization method-transient photo-resistivity spectroscopy, which we recently developed. This method measures directly the capture process of deep centers. In GaAlAs, apparent capture barrier energy EB= 0.25eV of DX center was determined and intrinasic capture barrier energy E$\sigma$ = 0.16eV was directly measured. In GaInAs, a defect with capture barier energy EB= 0.2BeV was observed. The result proved that DX centers capture electron only from band L, belonging to small lattice relaxation model. The theoretical deduction of transient photo-resistivity spectroscopy was improved.

ATOMIC AND MOLECULAR PHYSICS

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EXAFS STUDY OF THE LOCAL STRUCTURE NANOCRYSTALLINE FeZrB(Cu) SOFT MAGNETIC ALLOYS HU XIAO-JUN (胡小军), WU QIU-LIN (邬秋林), JI YU (季雨), MAN YI-JUN (满一军), YU KE (虞科), LING GANG (凌刚), YANG GUO-BIN (杨国斌), WANG RUN (王润), XIE YA-NING (谢亚宁) Acta Physica Sinica (Overseas Edition), 1996, 5 (1):  10-14.  DOI: 10.1088/1004-423X/5/1/002 Abstract ( 1093 )   PDF (145KB) ( 465 )   The changes of local structures around Fe and Zr atoms in the nanocrystalline films of Fe85Zr9B6 and Fe84Zr9B6 Cu1 alloys during annealing process were investigated by extended X-ray absorption fine structure (EXAFS) technique. It is confirmed that Zr atoms always exist in amorphous phase and do not dissolve in the bcc $\alpha$-Fe crystalline phase. The addition of 1 at% Cu lowers the crystallization temperature.

CLASSICAL AREAS OF PHENOMENOLOGY

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SUPERRADIANCE EFFECT OF THE CRYSTAL-LIKE-GAS LING TIAN (凌天), GUO GUANG-CAN (郭光灿) Acta Physica Sinica (Overseas Edition), 1996, 5 (1):  15-23.  DOI: 10.1088/1004-423X/5/1/003 Abstract ( 1082 )   PDF (173KB) ( 323 )   Crystal-like-gas (CLG) is a new kind of matter in which the atoms are arranged periodically in the space and the electrons are bound to the corresponding atoms. In this paper, we study the superradiance effect of CLG and discuss some interesting new properties due to the periodic structure of CLG. The non-ideal situation is also discussed.

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ASYMMETRIC CONTROL CHARACTERISTICS OF DYE BDN ON THE TWO TRAVELLING WAVES IN A RING YAG LASER HUANG MAO-QUAN (黄茂全), ZHENG JIN-LING (郑晋玲), LI RUI-NING (李瑞宁), GAO JIANG-RUI (郜江瑞), ZHANG KUAN-SHOU (张宽收), SU DA-CHUN (苏大春), Acta Physica Sinica (Overseas Edition), 1996, 5 (1):  24-30.  DOI: 10.1088/1004-423X/5/1/004 Abstract ( 1210 )   PDF (142KB) ( 360 )   It is discovered experimentally that, when placing a plate of dye BDN in a ring YAG laser cavity, the dye shows asymmetric control actions on the clockwise and counter-clockwise travelling waves. Unidirectional dye Q-switched operation is realized in a ring cavity based on this property without the use of Faraday rotator, polarizer and half-wave plate. A simplified theoretical analysis of this phenomenon is presented.

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PHASE SPACE ANALYSIS OF FREE ELECTRON LASER EFFICIENCY REDUCTION DUE TO RANDOM FIELD ERROR HU SU-XING (胡素兴), FU EN-SHENG (傅恩生) Acta Physica Sinica (Overseas Edition), 1996, 5 (1):  31-38.  DOI: 10.1088/1004-423X/5/1/005 Abstract ( 1073 )   PDF (206KB) ( 438 )   Considering the random field error of the wiggler, we deduce the equation of phase motion and calculate the phase volume of interaction in a real helical wiggler. The result was compared with the case of the ideal wiggler field. We analyze how the random field error causes the efficiency of free electron laser (FEL) to reduce, and simulate the FEL efficiency reduction effect according to the mechanisms which we present in this paper. The consequence agrees excellently with the experiment.

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EXPERIMENTAL STUDY ON THE SELF-MODE-LOCKED Ti:SAPPHIRE LASER XING QI-RONG (邢岐荣), ZHANG WEI-LI (张伟力), LU WEI (卢炜), K.M.YOO, J.LUENG Acta Physica Sinica (Overseas Edition), 1996, 5 (1):  39-45.  DOI: 10.1088/1004-423X/5/1/006 Abstract ( 1188 )   PDF (223KB) ( 429 )   The role of gain aperture in self-mode-locked Ti:sapphire laser was verified in our experiments. The observation of self-Q switching of self-mode-locked Ti:sapphire laser is reported. And tuning pulse duration from 50fs to 14.5ps was achieved.

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THEORETICAL INVESTIGATION OF SOLID FEMTOSECOND LASER AMPLIFIER ZHAO YING-QIAO (赵应桥), ZHANG RUO-BIN (章若冰), WANG QING-YUE (王清月) Acta Physica Sinica (Overseas Edition), 1996, 5 (1):  46-57.  DOI: 10.1088/1004-423X/5/1/007 Abstract ( 1206 )   PDF (355KB) ( 360 )   In this article, we present a theoretical description of the various effects on femtosecond light pulse during its propagating through a long solid gain medium on the basis of Maxwell equations and rate equations, By numerical simulation, we analyzed the variation of pulse energy, pulse duration. pulse shape and spectral distribution due to gain saturation, spectral narrowing, phase-shift induced by gain, group-velocity dispersion and self-phase modulation.

PHYSICS OF GASES, PLASMAS, AND ELECTRIC DISCHARGES

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THE DECISIVE ROLE OF m= 1 AND 2 PERTURBATIONS IN DENSITY LIMIT DISRUPTIONS ON TEXTOR KUANG GUANG-LI (匡光力), G.WAIDMANN Acta Physica Sinica (Overseas Edition), 1996, 5 (1):  58-70.  DOI: 10.1088/1004-423X/5/1/008 Abstract ( 1205 )   PDF (433KB) ( 373 )   The behavior of magnetohydrodynamic phenomena associated with disruptions of ohmically heated density limit discharges (qa=3.9) in the TEXTOR tokamak has been investigated in detail. A minor disruption is demonstrated to be only due to an m = 2 mode instability, possibly due to the magnetic reconnection of an m=2 island. When the m = 2 mode oscillations cease, the internal m = 1 kink mode instability is drastically enhanced at once, twisting the plasma core considerably. If the twisting is too strong, the twisted plasma core is inevitably displaced to the outside and brings cold plasma to the central region, leading to the energy quench at a major disruption.