基于GaSe和GaSe_(0.7)S_(0.3)单晶的单脉冲CO_2激光倍频器(英文)

描述了使用电感储能发生器和半导体转换开关泵浦的工作波长为10.6μm的高效CO2激光器。给出了激光泵浦的非线性晶体GaSe和GaSe0.7S0.3的二次谐波振荡的实验数据和理论估算结果。结果显示,GaSe晶体在输入能量为180mJ时,最大能量转换效率为0.38%,倍频激光的峰值功率为8 kW。     

GaSe晶体的双光子吸收对太赫兹输出的影响

根据光整流效应,利用超快激光脉冲泵浦GaSe晶体实现了0.2~2.5 THz的宽带太赫兹辐射输出。禁带中的电子在两个800 nm光子的作用下激发到导带中形成自由载流子,进而吸收所产生的太赫兹辐射,最终导致太赫兹的输出随泵浦功率的增加而趋于饱和。为了研究双光子吸收对太赫兹输出的影响,测量了800 nm处的GaSe晶体的双光子吸收系数,结果为 0.165 cm/GW。通过对太赫兹输出实验数据的拟合,得到GaSe晶体中自由载流子对太赫兹输出的吸收截面为1×10^-15 cm²。本文的研究结果可用于优化GaSe晶体在强激光泵浦下的太赫兹转换效率。     

Al、S和Te掺杂GaSe晶体的光学及倍频特性

对不同浓度Al、S和Te掺杂GaSe晶体的透过率和倍频特性进行了研究.结果表明,适宜浓度的掺杂晶体在透明波段内吸收系数约为α≤0.1~0.2cm-1,适于非线性应用.GaSe∶S晶体透过率曲线向短波方向移动,且更适于高浓度掺杂,而Al和Te掺杂晶体透明范围的波段截止波长向长波方向移动,且移动幅度小于S掺杂晶体,当掺杂浓度达到GaSe∶Al(0.5mass%)和GaSe∶Te(5mass%)时,晶体光学质量明显下降.通过fs Ti∶Sapphire激光和CO2激光泵浦下I类倍频实验发现,S掺杂晶体相位匹配曲线向短波方向移动,倍频输出功率比纯GaSe晶体有明显提高,最佳掺杂浓度为2mass%.Al和Te掺杂晶体相位匹配角与纯GaSe晶体相比没有明显变化,实验结果与理论曲线符合较好.利用非线性方法研究发现当掺杂浓度不超过5mass%时,GaSe∶Te晶体与纯GaSe同样属于六角形结构.三种掺杂方式最佳掺杂浓度分别为GaSe∶Al(0.1mass%),GaSe∶S(2mass%)和GaSe∶Te(0.5mass%),在CO2激光泵浦下,三者频率转换效率之比约为1∶0.6∶0.5.在所使用的晶体样本中,GaSe∶S(2mass%)晶体性能最佳,其频率转换效率可达纯GaSe晶体的3倍左右.     

GaSe：AgGaSe_2晶体的光学性能及应用（英文）

从GaSe∶AgGaSe₂熔体(质量掺杂浓度为10%)中生长的非线性光学晶体ε-GaSe∶Ag晶体(质量掺杂浓度≤0.04%)是一种非中心对称晶体,可用于相位匹配频率转换。Ag的掺入使GaSe晶体的显微硬度提高了30%,从而使其可以在任意方向上进行切割和抛光。本文研究了GaSe∶AgGaSe₂晶体在可见、中红外及太赫兹波段的光学性能。实验证明:GaSe∶AgGaSe₂晶体的吸收系数是纯GaSe晶体的2倍,其CO₂激光倍频效率是ZnGeP₂晶体的1.7倍。     

相位失配与材料吸收对利用GaSe差频产生太赫兹波功率影响的研究

从理论上分析了相位失配与材料吸收在利用GaSe非线性差频产生太赫兹(THz)波中的影响,计算得到了4种不同情况下的晶体最佳长度值和相应THz最大功率,计算了角度失配对于相位失配的影响,计算结果为非线性光学差频实验提供了重要参考依据和理论设计基础. 关键词： 太赫兹波 GaSe晶体 相位失配 材料吸收     

线性缀加平面波方法对GaSe晶体电子结构的计算

在密度泛函理论(DFT)广义梯度近似(GGA)下,用全势线性缀加平面波(FP-LAPW)方法计算了Ⅲ～Ⅳ族层状化合物GaSe晶体ε相的能带结构.计算得到的能隙宽度(1.015eV)以及布里渊区高对称点处的能量值,与最近的理论计算结果和实验数据符合得较好.     

基于GaSe和ZnGeP2晶体差频产生可调谐太赫兹辐射的理论研究

基于非线性光学频率变换理论,采用已报道的利用非线性光学差频方法产生可调谐太赫兹波的实验条件作为理论分析的实验模型,计算模拟出在不同相位匹配条件下,GaSe和ZnGeP₂晶体差频的相位匹配角、走离角、允许角和有效非线性系数,并对计算结果进行了分析比较,总结出对应输出不同太赫兹波长的最佳相位匹配方式.计算结果为利用非线性晶体差频产生可调谐太赫兹辐射的实验研究提供深入和全面的理论基础. 关键词： 太赫兹波 GaSe晶体 2晶体')" href="#">ZnGeP₂晶体 差频     

基于GaSe和ZnGeP2晶体差频产生可调谐太赫兹辐射的理论研究

基于非线性光学频率变换理论,采用已报道的利用非线性光学差频方法产生可调谐太赫兹波的实验条件作为理论分析的实验模型,计算模拟出在不同相位匹配条件下,GaSe和ZnGeP2晶体差频的相位匹配角、走离角、允许角和有效非线性系数,并对计算结果进行了分析比较,总结出对应输出不同太赫兹波长的最佳相位匹配方式.计算结果为利用非线性晶体差频产生可调谐太赫兹辐射的实验研究提供深入和全面的理论基础.     

太赫兹时域光谱技术研究S掺杂GaSe晶体的电导率特性

本文采用透射式太赫兹时域光谱技术研究0.3—2.5 THz范围内本征GaSe,S掺杂质量分数为2.5%GaSe(GaSe:S(2.5%))和S掺杂质量分数为7%GaSe(GaSe:S(7%))晶体的电导率特性,并利用Drude-SmithLorentz模型对复电导率进行拟合.研究发现GaSe晶体的电导率实部随S掺杂浓度的增大而减小,主要是由于S掺杂使GaSe晶体的费米能级逐渐向电荷中性能级转移,载流子浓度下降引起的.本征GaSe和GaSe:S(2.5%)在约0.56 THz处有明显的晶格振动峰,而GaSe:S(7%)在0.56 THz附近无晶格振动峰,这主要是由于S掺杂提高了晶体的结构硬度,减弱了晶体的层间刚性振动.且3个样品均在约1.81 THz处存在明显的窄晶格振动峰,强度随S掺杂浓度的增大先减小再增大,主要是由于S掺杂降低了GaSe的局部结构缺陷,减弱了窄晶格振动峰强度,而过量的S掺杂生成β型GaS晶体,进而增加晶体的局部结构缺陷,窄晶格振动峰强度随之增强.GaSe晶体约在1.07 THz和2.28 THz处的宽晶格振动峰强度随S掺杂浓度的增大而减弱甚至消失,主要是由于S掺杂产生...     

双掺Nd:Ce:YAG晶体激光输出特性

 为提高固体激光器的能量利用率,增大输出能量,将双掺Nd:Ce:YAG晶体的输出特性与普通Nd:YAG晶体进行了对比研究。分析了Nd³⁺和Ce³⁺的吸收光谱对激光晶体初始阈值反转粒子数的影响,结果显示:双掺Nd:Ce:YAG晶体可以提高晶体对泵浦光能量的利用率及激光器的输出能量,且可降低阈值泵浦能量。并分别检测了Nd:Ce:YAG激光晶体与Nd:YAG晶体的输出激光能量和阈值泵浦能量,实验结果表明：在输入电压为750 V时,Nd:Ce:YAG晶体与Nd:YAG晶体的输出能量分别为651.5 mJ 和390.4 mJ,能量利用率分别为2.31%和1.38%,激光振荡需要的泵浦能量阈值分别为10.56 mJ和15.21 mJ,且普通Nd:YAG晶体的斜效率为0.36%,而双掺Nd:Ce:YAG晶体的为0.49% 。     

Formation and development of laser physics at Tomsk University

The formation of the laser school in the Siberian Physical-Technical Institute at Tomsk State University is considered in historical perspective. The most important achievements and publications are discussed. The role of Siberian Conferences on Spectroscopy held regularly under the supervision of Prof. N.A. Prilezhaeva in the development of laser physics at Tomsk University and in the city of Tomsk is demonstrated. Tomsk State University; the V. D. Kuznetsov Siberian Physical-Technical Institute at Tomsk State University. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 8, pp. 4–13, August 1999.     

掺碲硒化镓晶体的光学性能

采用水平区熔法生长了碲（Te）掺杂浓度（质量百分比）分别为0.05%,0.1%,0.5%,1%,2%的硒化镓（GaSe）晶体,并分别对掺杂浓度为0.01%,0.07%,0.38%,0.67%,2.07%的GaSe∶Te晶体的光学性能进行了表征。首次研究了GaSe∶Te晶体中刚性层声子模式的转换。吸收光谱测试结果表明：当Te掺杂浓度小于0.38%时,振动中心位于0.59 THz附近的E＇（2）刚性模式吸收峰强度可达最大值,这一过程与GaSe∶Te晶体光学性能的提高密切相关。但Te掺杂浓度的进一步提高会导致E＇（2）刚性模式吸收峰强度逐渐减弱,当Te掺杂浓度为1%时,E＇（2）刚性模式吸收峰基本消失。这两个过程与GaSe∶Te晶体光学质量的下降密切相关。因此,E＇（2）刚性模式吸收强度达到最高时对应的掺杂浓度即是GaSe∶Te晶体中Te的最佳掺杂浓度,光整流产生太赫兹过程证实了此结论的正确性。     

Conceptual basis for regional monitoring of climatoecological measurements

A discussion is presented of the scientific, technological, and instrumental aspects of regional monitoring of climatoecological measurements of the Earth's atmosphere. By way of an example we present the observed trends in measurements of the average annual temperature in Tomsk, the Siberian region, and Russia over a period of several decades, and also the trends in the amount of cloud cover and the overall ozone content in the territory of Russia. Institute of Optical Monitoring, Siberian Branch of the Russian Academy of Sciences, Tomsk State University. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 9, pp. 61–70, September, 1998.     

Scattering of electromagnetic waves by a perfectly conducting body with a chiral coating

We propose a numerical method for solving problems of electromagnetic scattering in the resonance spectrum of frequencies by a 3D ideally conducting arbitrary-shaped body covered by a homogeneous chiral coating. A program package for calculating the characteristics of the scattered field and checking the accuracy of the obtained solution based on the above method is described briefly. Some results of numerical calculations are given, which are useful for a study of the influence of “chirality” on the scattering properties of absorbing coatings. Siberian Physical-and-Technical Institute at Tomsk State University, Tomsk, Russia. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 41, No. 4, pp. 495–506, April, 1998.     

Distortion deformations in the B2-R phase transition in titanium nickel alloys

Based on x-ray analysis, we have calculated the lattice distortions in Ti-Ni-Me (Me=Rh, Co, Fe) alloys during the B2-R phase transition. We find that, during the transition, the deformation decreases as the concentration of the alloying component increases in Ti-Ni-Rh and Ti-Ni-Co. No such correlation is observed in the Ti-Ni-Fe alloys. Tomsk State Architecture-Construction Academy. V. D. Kuznetsov Siberian Physicotechnical Institute, Tomsk State University. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 2, pp. 95–100, February, 1997.     

Some problems of spectral estimation

The main problems of spectral estimation are considered. It is shown that these problems arise from sample limitation and finiteness of the frequency band. We suggest that the signal spectrum composition should be described by the distribution function of oscillation density instead of the traditionally used complex spectrum and spectral power density. Siberian Physical and Technical Institute of Tomsk State University, Tomsk, Russia. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 40, No. 7, pp.925–930, July, 1997.     

Influence of nonhydrostatic stresses on the development of martensitic transformations and inelastic strains at various levels in Ti(Ni-Cu-Fe) polycrystalline intermetallic compounds

The levels of inelastic martensitic strain of polycrystals during a thermoelastic martensitic transformation under a load are discussed. The example ofTi(Ni-Cu-Fe) alloys with the B2 structure was used to study the role of microlevel and mesolevels in inelastic martensitic deformation during cooling of polycrystals under a load and loads in different initial structural states. V. D. Kuznetsov Siberian Physicotechnical Institute at Tomsk State University. Institute of Physics of Strength of Materials and Materials Science, Siberian Branch of the Academy of Sciences of the USSR, Tomsk. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 1, p. 35–46, January, 1998.     

A minimax approach in the theory of the excited states of many-electron systems

Theorems are stated and proved that allow one to determine the saddle points of energy functionals for excited states and to select the particular saddle point that provides a improvable upper bound to the characteristic eigenvalue of the Hamiltonian. A general minimax approach, based on the proved theorems, is proposed for calculating the excited states of many-electron systems having lower-lying states of the same symmetry.Tomsk Pedagogical Institute. V. V. Kuibyshev Tomsk State University. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 11, pp. 35–41, November, 1992.     

Instability of the crystal lattice of CuPd alloy

The results of structural investigations (x-ray structural analysis, small-angle scattering and electron microscopy) of the B2→Al deformation phase transition and the kinetics of the recovery processes of deformed CuPd alloy are presented. It is established that the phase transition occurs in regions of local plastic deformation and the B2→Al deformation transition helps to enrich these regions with palladium. Tomsk State Architecture-Construction Academy. V. D. Kuznetsov Siberian Physico-Technical Institute, Tomsk University. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 3, pp. 93–102, March, 1997.     

Design principles of tunable interference light filters

Tunable interference light filters [1–5] hold a special place among the multitude of light filters because they combine the advantages of light filters and dispersing prisms (diffraction gratings). Those light filters can monochromatize light in broad light beams and can smoothly vary the wavelength. V. D. Kuznetsov Siberian Physicotechnical Institute at Tomsk State University. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 3, pp. 3–10, March, 1997.