共查询到20条相似文献,搜索用时 15 毫秒
1.
The properties of a coplanar-pumped folded-slab laser under the influence of thermal lensing have been modeled and measured. It is shown that despite the formation of a strong astigmatic lens within the slab, the results can be used to design resonators capable of good TEM00 performance, suitable for a wide variety of applications. Good agreement is found between modeling and measurement of slab and laser parameters. Using a novel technique, the fraction of absorbed pump power converted to heat has been measured under diode-laser pumping 相似文献
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The slab geometry laser--Part I: Theory 总被引:6,自引:0,他引:6
Eggleston J. Kane T. Kuhn K. Unternahrer J. Byer R. 《Quantum Electronics, IEEE Journal of》1984,20(3):289-301
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In a practical circuit, the output noise due to the thermal noise of a resistor will depend on the actual transfer function of the noise source. The bandwidth will never be infinite because the transfer function of either the noise source or the device measuring the output noise will cause limitations. Consequently, the thermal noise voltage of a resistor in a finite bandwidth is maximum for a given resistor value. That maximum thermal noise voltage depends on the stop frequencies and decreases for both smaller and larger resistor values 相似文献
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《Microelectronics Journal》2002,33(1-2):161-170
The formula for quantum efficiency in a semiconducting material was first derived by Seib in 1974 for a semi-infinite slab of semiconducting material. Seib's first-order analysis considered the effect of absorption coefficient, minority carrier diffusion length and depletion width. However, for modern devices on epitaxial material, smart sensors, quantum well devices, etc., the semi-infinite slab approximation breaks down. Here, we present the derivation for a finite slab that considers the thickness of the layer as a fourth parameter. We present a case study analyzing quantum efficiency, and hence MTF, in epitaxial silicon versus bulk gallium arsenide. 相似文献
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Static gas conduction cooled slab geometry Nd:glass laser 总被引:1,自引:0,他引:1
We report on the first demonstration of a 10 Hz static gas cooled slab geometry Nd:glass laser. This cooling approach provides thermal control of the slab laser medium while eliminating mounting and optical problems associated with liquid cooling. 相似文献
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Tranquillo JV Burwell DO Henriquez CS 《IEEE transactions on bio-medical engineering》2005,52(2):334-338
Extracellular potentials are often used to assess the activation and repolarization of transmembrane action potentials in cardiac tissue under a variety of experimental conditions. An analytical model of the extracellular potentials arising from a planar wavefront propagating in a three-dimensional slab of cardiac tissue with a variably thick adjacent volume conductor or bath is presented. Starting with the transmembrane potential, the model yields the extracellular potentials at various points in the bath and inside tissue. The results show that the analytical model produces signal timecourses with trivial computational costs that are similar to those computed from a full reaction-diffusion bidomain model with different bath thicknesses for tissue with uniform properties and for tissue with an abrupt ionic inhomogeneity. 相似文献
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Reduced thermal focusing and birefringence in zig-zag slab geometry crystalline lasers 总被引:4,自引:0,他引:4
Replacing the rod in a Nd:YAG laser with a zig-zag slab resulted in a very substantial reduction of the thermally induced optical distortion without sacrifice of output power or efficiency. This reduction was possible after simple measures were taken to eliminate end and edge effects. 相似文献
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使用8条激光二极管(LD)阵列对Nd:YAG晶体进行双侧泵浦,分析晶体的温度、应力和热致折射率的变化.研究不同泵浦条件下放大器的放大系数,并在此基础上,重点讨论了热效应对晶体寄生振荡的影响.实验结果表明,在高功率泵浦的条件下,由晶体热效应引起的晶体变形及热致折射率变化可以在一定程度上抑制晶体的寄生振荡.不管振荡器输出光是直线通过放大器还是在放大器晶体表面反射一次通过晶体,均能得到2倍的单程放大系数. 相似文献
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《IEEE transactions on information theory / Professional Technical Group on Information Theory》1971,17(3):332-336
In this paper, an improved decoding algorithm for codes that are constructed from finite geometries is introduced. The application of this decoding algorithm to Euclidean geometry (EG) and projective geometry (PG) codes is further discussed. It is shown that these codes can be orthogonalized in less than or equal to three steps. Thus, these codes are majority-logic decodable in no more than three steps. Our results greatly reduce the decoding complexity of EG and PG codes in most cases. They should make these codes very attractive for practical use in error-control systems. 相似文献
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Construction of nonbinary cyclic, quasi-cyclic and regular LDPC codes: a finite geometry approach 总被引:1,自引:0,他引:1
Lingqi Zeng Lan Lan Ying Yu Tai Bo Zhou Shu Lin Abdel-Ghaffar K.A.S. 《Communications, IEEE Transactions on》2008,56(3):378-387
This paper presents five methods for constructing nonbinary LDPC codes based on finite geometries. These methods result in five classes of nonbinary LDPC codes, one class of cyclic LDPC codes, three classes of quasi-cyclic LDPC codes and one class of structured regular LDPC codes. Experimental results show that constructed codes in these classes decoded with iterative decoding based on belief propagation perform very well over the AWGN channel and they achieve significant coding gains over Reed-Solomon codes of the same lengths and rates with either algebraic hard-decision decoding or Kotter-Vardy algebraic soft-decision decoding at the expense of a larger decoding computational complexity. 相似文献
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以解析热分析理论为基础,建立了平板Nd:LuVO4晶体在激光二极管阵列双侧泵抽运时的导热微分方程。通过方程求解,得到平板Nd:LuVO4晶体内部温度场分布的解析式及热形变分布。温度场和热形变场的数值模拟表明:当泵浦光平均功率Po=10 W、泵浦区域为1 mm×1 mm时,四组激光二极管阵列光源在三处不同位置的一维温度场、二维温度场分布和热形变量有很大差异;将三处泵浦光源位置所产生的温度分布和热形变量对比,得到了泵浦光源在位置1、2处所产生的温升和热形变量相对较小,位置3处最大。所得结论可为平板Nd:LuVO4激光器的设计及热效应消除提供理论依据。 相似文献
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《Solid-State Circuits, IEEE Journal of》1985,20(4):865-870
The influence of random edge effects and oxide thickness variations on MOS transistor characteristics is investigated. The variance of the drain current is calculated as a function of the parameters of the stochastic geometry effects. Finally, the relation with the scaling down of the transistor dimensions is also included. 相似文献
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The focal length of the thermal lens and the beam quality factor (beam propagation factor) M2 for a multiple longitudinally diode pumped slab laser is deduced for pump and output powers up to 16 and 4.5 W, respectively. Due to the geometry of the arrangement, a stronger thermal lens is observed in the plane with the larger pump spot radius as predicted by an analytical model for slab geometries. In addition, the second stable zone of an asymmetric resonator is found to be advantageous for improved beam properties at high output powers 相似文献
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讨论了随机降雨层中的电磁波矢量辐射传输问题。根据一种具有两种降雨强度大小的随机降雨层模型,建立相应的矢量辐射传输方程,给出了一种求解方法。用Monte Carlo方法验证了该方法的正确性,讨论了随机降雨层和确定降雨层之间的区别和联系以及随机降雨层参数变化对结果的影响,最后讨论了随机介质和两种平均介质之间的关系。 相似文献
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Shu-Tao Xia Fang-Wei Fu 《Communications Letters, IEEE》2006,10(5):381-383
In this letter, the stopping sets and stopping distance of finite geometry LDPC (FG-LDPC) codes are studied. It is known that FG-LDPC codes are majority-logic decodable and a lower bound on the minimum distance can be thus obtained. It is shown in this letter that this lower bound on the minimum distance of FG-LDPC codes is also a lower bound on the stopping distance of FG-LDPC codes, which implies that FG-LDPC codes have considerably large stopping distance. This may explain in one respect why some FG-LDPC codes perform well with iterative decoding in spite of having many cycles of length 4 in their Tanner graphs. 相似文献
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Bozzetti M. Costantini G. D'Orazio A. De Sario M. Petruzzelli V. Prudenzano F. Renna E. 《Electronics letters》2003,39(6):488-490
The influence of the grounded dielectric substrate finite size on the surface-wave propagation in a microstrip patch antenna is investigated. A simple model that interprets this phenomenon is developed. To reduce surface mode levels and to improve the antenna gain and the radiation pattern, an electromagnetic bandgap structure consisting of a two-dimensional periodic pattern of circles etched in the ground plane of the antenna is adopted. 相似文献