共查询到20条相似文献,搜索用时 15 毫秒
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利用双温方程对激光烧蚀Si靶的过程进行了数值模拟,并结合合适的初始条件和边界条件,研究了在飞秒、皮秒激光作用下,脉冲波形(矩形、梯形、三角形和高斯形)对Si靶表面载流子和晶格温度分布的影响。结果表明:激光功率密度是影响载流子温升的主要因素,矩形脉冲激光烧蚀Si靶表面载流子的峰值温度最高,而高斯分布的脉冲引起靶面载流子峰值温度最低。可见,激光脉冲波形对Si靶表面载流子的温度分布具有重要影响。所得结果可为制备高质量的薄膜提供理论依据。 相似文献
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为研究多物理参数(耦合系数、电子热导率、电子热容、晶格热容)同时随温度变化对短脉冲激光辐照金属材料产生温度场分布的影响,基于双温耦合理论,建立了短脉冲激光辐照金属材料金的加热过程的有限元求解模型。在同时考虑脉冲激光的空间、时间分布和多参数同时随温度变化的情况下,得到短脉冲激光辐照金属材料金激励产生的温度场二维瞬态分布,并进一步比较了多物理参数同时随温度变化和采用室温物理参数两种情况下温度场分布的区别。数值结果表明:多物理参数同时随温度变化使电子温度和晶格温度的上升变快,最大值变大,而且使得材料中激光穿透直接辐照到的区域温度变高。 相似文献
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Stefan J. Rupitsch Reinhard Lerch 《Applied Physics A: Materials Science & Processing》2009,97(4):735-740
A novel Inverse Method for the determination of material parameters characterizing discoidal piezoceramic actuators is presented.
In contrast to the common identification method, no specially shaped test samples are required. The Inverse Method is based
on a finite element simulation. Both the measured mechanical and the electrical behavior of the actuator serve as input quantities
of the new procedure. The presented results show the efficiency and correctness of the developed Inverse Method. 相似文献
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This Letter investigates the problem of synchronization in complex dynamical networks with time-varying delays. A periodically intermittent control scheme is proposed to achieve global exponential synchronization for a general complex network with both time-varying delays dynamical nodes and time-varying delays coupling. It is shown that the sates of the general complex network with both time-varying delays dynamical nodes and time-varying delays coupling can globally exponentially synchronize with a desired orbit under the designed intermittent controllers. Moreover, a typical network consisting of the time-delayed Chua oscillator with nearest-neighbor unidirectional time-varying delays coupling is given as an example to verify the effectiveness of the proposed control methodology. 相似文献
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超短脉冲染料放大器中的参数研究 总被引:1,自引:0,他引:1
对超短脉冲染料放大器(DLA)中放大的自发辐射(ASE)随泵浦强度变化的关系进行了实验研究,为了求得具有高储能、低自发辐射背景噪声的染料激光放大器的泵浦强度,我们用速率方程对实验结果进行了解析分析,获得了染料激光放大器的泵浦强度与染料参数(浓度、增益长度等)的近似关系式,以及相应条件下染料激光放大器储能和小信号增益的表达式,并与实验进行了比较.二者符合较好,从而为染料激光放大器的设计提供了参考. 相似文献
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A novel method for obtaining a single shot multi-point high dynamic range pulse contrast measurement is presented. We use Dammann gratings to generate multiple beamlets by division of amplitude on ultrashort laser pulses. The analysis results show that this method can achieve high dynamic range in pulse contrast measurement on a single shot by using photomultiplier tube (PMT) detectors and the long working distances to minimize cross talk between channels. Some distortion of pulse shape is also analyzed detailedly with the Dammann grating and its compensation grating, which may degrade the pulse contrast measurement in some degree by pulse stretching and spectrum clipping. 相似文献
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A. Schoonderbeek C.A. Biesheuvel R.M. Hofstra K.-J. Boller J. Meijer 《Applied Physics A: Materials Science & Processing》2005,80(4):769-775
After the development of a novel XeCl excimer laser with a nearly diffraction-limited beam and 175 ns pulse length, research was done on different industrial applications of this laser. Hole drilling, one of these applications, was studied extensively. A better understanding of the drilling process is necessary to optimise the drilling efficiency and to control the quality of the holes. A shadowgraphic imaging technique was used for studying the removal of material from the hole and the absorption of the laser beam by this removed material. Images were made at successive times both during and after the laser pulse.In drilling of thin foils, it was shown that the material was ejected mainly after the laser pulse. A comparison of different materials showed that the drilling process should be optimised for each material independently. Furthermore, the plume was found to be not fully transparent for processing materials with a strong absorption line at or near the laser wavelength. The correlation between material and drilling speed suggests improved energy transfer and improved melt ejection for the materials with this absorption. PACS 42.62.Cf; 52.38.Dx; 52.38.Mf 相似文献
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An algorithm in the form of inverse problem to estimate the surface emissivity versus temperature of solids of variable thermal properties separated by a non-participating medium is proposed. The estimations are reproduced by the connection of variable slope stretches (piece-wise function) with no information of the temperature dependence of the emissivity. The input data (measurements) come from the solution of the direct problem by adding a random error to the temperature field. Both the direct and inverse problem are numerically solved by means of the network simulation method. The influence of different parameters in the estimation is studied and the resulting estimations are compared with exact solutions in order to verify the effectiveness of the proposed method. 相似文献
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The light pulse generation by a laser controlled by shutter from a finite-thickness absorbing layer with thermal nonlinearity has been studied theoretically. The layer placed in the cavity is oriented with respect to the mirror so that conditions for nonlinear total internal reflection of generated radiation are created. In the plane-wave approximation, a self-consistent system of nonlinear truncated equations for the field amplitudes together with constitutive equations has been obtained. Numerical simulation with the use of the obtained system has shown that it is possible to control the form and duration of the generated pulse by varying the absorption coefficient of the nonlinear medium and the angle of incidence on the absorbing layer, as well as the layer thickness.Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 71, No. 6, pp. 771–777, November–December, 2004.This revised version was published online in April 2005 with a corrected cover date. 相似文献
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A. M. Silaev 《Radiophysics and Quantum Electronics》1995,38(7):450-461
The problem of optimal estimation of the parameters of a nonstationary sequence of random pulses observed additively with the noise is considered with the step change in average pulse repetition rate taken into account. A recurrent algorithm is derived for optimal estimation of the pulse repetition rate and time of its jump in real time. The optimal assessment of the Bernoulli trial parameters is shown as an example. The results of computer simulation experiments are presented.Lobachevsky State University, Nizhny Novgorod. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 38, No. 7, pp. 678–694, July, 1995. 相似文献
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Philip L. Varghese Ronald K. Hanson 《Journal of Quantitative Spectroscopy & Radiative Transfer》1984,31(6):545-559
A tunable infrared diode laser was used to record 17 fully resolved vibration-rotation transitions in the v1 fundamental band of HCN at 3μ. The experiments were conducted in an absorption cell on room temperature mixtures of HCN diluted by N2 and Ar. The v1 fundamental band strength of HCN was determined to be 267±8 cm-2 atm-1 at 273.2 K. Small but significant reductions in the residual errors were obtained by using the Galatry profile rather than the Voigt profile to fit the experimentally recorded line shapes. Collisional broadening and narrowing parameters were determined simultaneously from Galatry profile fits to the data. The collision-broadened linewidths of HCN lines in N2 and Ar were determined as a function of rotational quantum number of transitions ranging from P(14) to R(14) (3268.22-3353.29 cm-1). The optical diffusion coefficients of HCN in N2 and Ar at 300 K were determined from the collisional narrowing parameters and were 0.074±0.01 and 0.016±0.03 cm2s-1 respectively. 相似文献
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利用麦克斯韦-布洛赫耦合方程,研究了激光脉冲在4,4′-二甲氨基二苯乙烯分子材料中的共振传播,探讨了激光脉冲在传播中的时空演化情况.在数值计算中考虑了各种阻尼效应. 相似文献
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This paper deals with the problem of heating a finite slab using laser radiation in relation to the parameters characterizing the laser pulse, namely: qmax(W/m2), the maximum laser power density, t0 the time interval required to reach qmax and td, the pulse time duration. The pulse shape q(t) is suggested in the form: q(t)=βqmax(t/td)(1-(t/td))exp-B(t-t0/td), where β and B are parameters. Fitting with published experimental pulse [Ready JF. Effects due to absorption of laser radiation. J Appl Phys 1965;36:462–68] is made. Fourier series expansion technique is considered to solve the problem. The critical time required to initiate melting tm is estimated for four metallic elements and five semiconductors, namely: Al, Cu, Ag, Au (aluminum, copper, silver, and gold), cadmium sulfide, germanium, silicon, alpha beryllium oxide, and silicon carbide. Five pulses with different characteristic parameters are considered.Computations revealed that the thermal response of the targets is highly affected by qmax and to, while the pulse time duration is less effective in determining the value of tm. Moreover, it is revealed that the relation between tm and the melting temperature for the same laser pulse is nonlinear for the considered targets under the indicated conditions. 相似文献
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