共查询到20条相似文献,搜索用时 31 毫秒
1.
V. S. Zemlyanskiĭ I. A. Khramtsovskiĭ A. N. Gorlyak A. A. Stepanchuk 《Optics and Spectroscopy》2008,105(2):320-325
The basic regularities of changes in the main ellipsometric parameters of a light beam reflected from inhomogeneous surface layers of silicate glasses have been described on the basis of the Drude-Born theories of polarized light reflection. A method of physicomathematical modeling of the refractive index profile in an inhomogeneous surface layer of silicate glasses is reported, which makes it possible to determine, with the lowest second-kind error probability, a model of an inhomogeneous reflecting system that is adequate to the object of study. 相似文献
2.
Reflecting a single attosecond pulse by using periodic Mo/Si multilayer mirrors with different layers 下载免费PDF全文
The reflecting of a single attosecond pulse from a periodic Mo/Si multilayer was investigated. By changing the number of bi-layers, the periodic multilayer showed greatly different spectral and temporal responses of the attosecond pulse reflection, which has been discussed in detail in this paper. The capability of attosecond pulse reflection of the periodic multilayers with different bi-layer numbers has been evaluated using suitable temporal parameters. In addition, the condition for obtaining high-efficiency reflected pulses has been analyzed by comparing the pulse responses of the periodic multilayer with different layers. The transfer-matrix method together with the fast Fourier transform has been used in our simulation. 相似文献
3.
Reflecting single attosecond pulse by periodic Mo/Si multilayer mirrors with different layers 下载免费PDF全文
The reflecting of single attosecond pulse from a periodic Mo/Si multilayer was investigated. With changing the number of bi-layers, the periodic multilayer showed greatly different spectral and temporal responses of the attosecond pulse reflection, which has been discussed in detail in this paper. The capability of attosecond pulse reflection of the periodic multilayers with different bi-layer numbers has been evaluated using suitable temporal parameters. In addition, the condition for obtaining high-efficiency reflected pulses has been analyzed by comparing the pulse responses of the periodic multilayer with different layers. The transfer-matrix method together with the fast Fourier transform has been used in our simulation. 相似文献
4.
Much effort is being made in the study of light propagation in human tissue due to the development and wide use of lasers for surgical and therapeutic applications. When a picosecond light pulse is incident on biological tissue, part of the light is reflected back owing to specular surface reflection and the rest of the light penetrates the tissue and encounters multiple scattering and absorption processes. An analysis has been presented for modeling of light distribution in human tissue. The influence of the refractive index, scattering phase function and scattering albedo on light distribution in laser irradiated tissue has been demonstrated. 相似文献
5.
Norihiro Fukuchi Ye Biqing Yasunori Igasaki Narihiro Yoshida Yuji Kobayashi Tsutomu Hara 《Optical Review》2005,12(5):372-377
We have developed optically-addressed and electrically-addressed liquid crystal spatial phase-only light modulators having
no pixelized structures. We obtained a large depth of phase-only modulation and high diffraction efficiency based on the electro-optical
characteristics of a parallel-aligned nematic liquid crystal. These spatial light modulators (SLM) are of the reflection type,
so there would be a loss of power in the readout light from the half mirror, which was set up so as to separate the incident
and reflected lights. To optimize the characteristics of a reflection type spatial phase-only light modulator, we have proposed
an oblique incident optical readout setup. We have examined the effect of conditions such as the polarization direction and
the incidence angle of the readout light, and the orientation of liquid crystal molecules in the SLM. High diffraction efficiency
close to the theoretical maximum value was obtained by adjusting the above conditions. The simulation analysis can well explain
the experimental results of phase modulation. 相似文献
6.
Behmke M an der Brügge D Rödel C Cerchez M Hemmers D Heyer M Jäckel O Kübel M Paulus GG Pretzler G Pukhov A Toncian M Toncian T Willi O 《Physical review letters》2011,106(18):185002
When a laser pulse hits a solid surface with relativistic intensities, XUV attosecond pulses are generated in the reflected light. We present an experimental and theoretical study of the temporal properties of attosecond pulse trains in this regime. The recorded harmonic spectra show distinct fine structures which can be explained by a varying temporal pulse spacing that can be controlled by the laser contrast. The pulse spacing is directly related to the cycle-averaged motion of the reflecting surface. Thus the harmonic spectrum contains information on the relativistic plasma dynamics. 相似文献
7.
The transformation of the envelope of a Gaussian pulse incident on and reflecting from a nonlinear dispersive medium is studied.
It is shown that the pulse envelope transforms considerably upon reflection near the optical resonance frequency and the nonlinearity
of the medium may appreciably distort the reflected pulse. Away from the resonance frequency, conditions may arise when the
shift of the reflected pulse does not lead to the loss of the Gaussian form. In this case, the influence of nonlinearity is
insignificant. 相似文献
8.
Improving attosecond pulse reflection by large angle incidence for a periodic multilayer mirror in the extreme ultraviolet region 下载免费PDF全文
The improvement of attosecond pulse reflection by large angle incidence for a periodic multilayer mirror in the extreme ultraviolet region has been discussed. Numerical simulations of both spectral and temporal reflection characteristics of periodic multilayer mirrors under various incident angles have been analyzed and compared. It was found that the periodic multilayer mirror under a larger incidence angle can provide not only higher integrated reflectivity but also a broader reflection band with negligible dispersion, making it possible to obtain better a reflected pulse that has a higher pulse reflection efficiency and shorter pulse duration for attosecond pulse reflection. In addition, by increasing the incident angle, the promotion of attosecond pulse reflection capability has been proven for periodic multilayer mirrors with arbitrary layers. 相似文献
9.
根据皮肤组织解剖结构特性建立了六层层状模型,并给出了皮肤组织各层的特性参数;考虑了氧合血红蛋白和还原血红蛋白的吸收特性,依据皮肤组织各层的水、血、脂肪、血氧饱和度含量以及血管大小给出了皮肤组织各层的光谱吸收系数;对不同波长散射系数做了适当简化,给出了皮肤组织各层的光谱散射系数。利用蒙特卡罗方法仿真血管组织在收缩与舒张两种状态下, 400~1 000 nm波长光在皮肤组织多层模型中的传输过程,并通过统计大量光子的分布特性,获得了皮肤组织光谱反射系数,并利用模拟所得的两种状态下的反射系数计算得到了光谱容积脉搏波幅度。仿真结果表明,当入射光强一定时,绿光的容积脉搏波幅度优于红光和蓝光。通过计算不同波长光沿皮肤组织深度方向光能流率衰减为1/e时对应的皮肤组织深度,获得了皮肤组织光谱穿透深度。结果显示,血管舒张状态下蓝光和绿光的穿透深度较小,蓝光大部分只能达到表皮层,绿光能到达微循环层,红光可直达真皮层。考虑到光在皮肤组织中传播包含了一个从收缩到舒张的动态过程,基于此,根据穿透深度定义了脉搏波信号产生深度,利用血管舒张与收缩两种不同状态下的穿透深度计算得到了光谱产生深度。结果表明,不同波长光产生深度大于其穿透深度,蓝光产生深度较浅,且其受到的血液吸收调制较小,因而其获得的脉搏信号易受噪声干扰;红光的容积脉搏波产生深度较大,但是相比于绿光其受血液吸收调制较小,且绿光产生深度足够达到真皮血管层,因而红光容积脉搏波的幅度小于绿光。上述仿真结果明确了皮肤组织部分光谱特性,为皮肤组织多光谱容积脉搏波的精确获取及其他相关研究提供了一定的理论基础。 相似文献
10.
Improving attosecond pulse reflection by large angle incidence for periodic multilayer mirror in the extreme ultraviolet region 下载免费PDF全文
The improvement of attosecond pulse reflection by large angle incidence for periodic multilayer mirror in the extreme ultraviolet region has been discussed. Numerical simulations of both spectral and temporal reflection characteristics of periodic multilayer mirrors under various incident angles have been analyzed and compared. It was found that the periodic multilayer mirror under larger incidence angle can provide not only higher integrated reflectivity but also broader reflection band with negligible dispersion, making it possible to obtain better reflected pulse that owns higher pulse reflection efficiency and shorter pulse duration for attosecond pulse reflection. In addition, with increasing of incident angle, the promoting of attosecond pulse reflection capability has been proven for periodic multilayer mirrors with arbitrary layers. 相似文献
11.
The reflection of light particles bombarding heavy targets has been investigated with the single-collision model, which assumes straight line trajectories between the surface and the large angle scattering event upon incidence and exit of the swift particle. This model allows analytical integration, under some approximations, to yield energy and angular distributions of reflected particles as well as particle and energy reflection coefficients in terms of analytical formulae. The results are compared with data from the Monte Carlo computer program TRIM for H and He incident on Au. This comparison shows that the model can be applied for reduced energies larger thanε=5, and that it is well suited for any higher energy up to relativistic energies, in contrast to previous theoretical or empirical formulae. 相似文献
12.
《Superlattices and Microstructures》1994,16(1):17-20
The resonant spectra of light reflected and transmitted by a heterostructure with a finite system of equidistant quantum wells have been calculated. Recurrence relations have been derived connecting the amplitude reflection coefficients from N and N - 2 quantum wells, and analytical properties of the reflection coefficient as a function of the complex frequency ω have been established. A method has been proposed which allows one to find complex frequencies of coupled exciton-photon nonstationary modes, or exciton-polaritons. It has been shown that the resonant Bragg structures represent a particular case where among N eigenmodes only one is radiative. 相似文献
13.
宽带飞秒脉冲双折射干涉滤波的研究 总被引:1,自引:1,他引:0
对宽带飞秒脉冲双折射干涉滤波进行了理论和实验研究。首先给出了一种新型的双折射干涉滤波器的原理和设计,得到了输出滤波光谱强度分布的解析表达式。然后进行了15fs宽带脉冲的干涉滤波的实验研究,实验得到了一组性能良好的透射和反射输出的干涉滤波谱图,实验测量与理论计算基本一致。同时还分析了群速失配以及色散对宽带飞秒脉冲双折射干涉滤波的影响。结果表明这种滤波器对宽带飞秒脉冲有很好的干涉滤波作用,能同时前向透射和侧向反射干涉滤波输出,且无插入功率损耗,可以用来获得波长稳定的多波长可调谐超短脉冲光源。对于飞秒脉冲干涉滤波器的设计和应用具有重要的参考价值。 相似文献
14.
15.
The 0-order transmission of a 1D metallic grating, on a high-resistivity silicon wafer in optical contact with a silicon plate, has been characterized by terahertz time-domain spectroscopy with subpicosecond resolution over a 400 ps scan range. Two new long-time-delay, powerful pulses are observed after the second reflected pulse. In the frequency domain, these two strong and fast-ringing structures correspond to the bandwidth ranges between the [0, 1] and [0, 2] surface plasmon modes and the range above [0, 2], respectively. A physical optics ray analysis provides an intuitive understanding of these new four-step (reflection, diffraction, total reflection, and diffraction) pulses, caused by fractional-order surface plasmon type beam coupling. 相似文献
16.
The interaction of intense, ultra-short laser pulses (USLP) with a surface of transparent dielectrics is considered. The combination of multi-photon absorption and impact ionization generates a plasma layer at the dielectric boundary. Interaction with the plasma self-consistently determines the amount of reflected, transmitted and absorbed light, and the spatial distribution of electron density. In the present paper, we model the interaction of USLP with transparent dielectrics. We calculate the evolution of electron density profiles and the variation of reflection, transmission and absorption of laser radiation during the pulse. We show that the laser-created surface plasma acts as a filter transmitting only the leading edge of the laser pulse. The transmitted energy is approximately fixed, nearly independent of input pulse energy. The transmitted energy increases with pulse duration. This increased energy is manifested in the formation of cylindrical shock waves directly applicable to recent experiments investigating absorption and shock generation in water. PACS 79.20.Ds; 81.15.Fg; 05.45.Pg 相似文献
17.
机载激光测深系统的最小可探测深度研究 总被引:3,自引:2,他引:1
针对回波特性进行理论分析和数值模拟,讨论影响机载激光测深系统的最小可探测深度的各种因素和解决的技术途径。采用窄激光脉冲,高速探测器,小接收视场角,可以改善海表和海底反射信号的叠加。分析海表和海底反射脉冲的特征,提出采用双高斯脉冲拟合方法,从叠加的回波信号中分离海表、海底反射信号,降低机载激光测深系统的最小可探测深度,满足海岸带测绘应用。利用实验室模拟装置进行测量实验,利用提出的方法分离表面和底部反射信号,得到0.4m的最小可探测深度。同时比较了雪崩二极管和光电倍增管的测量结果,两者的测量精度相当。 相似文献
18.
V. P. Afanas’ev A. V. Lubenchenko S. D. Fedorovich A. B. Pavolotskii 《Technical Physics》2002,47(11):1444-1452
The energy spectra of electrons reflected from multilayer targets are studied theoretically and experimentally. A self-consistent theory of electron reflection from multilayer surfaces is constructed. Simple analytical models of electron reflection that illustrate the feasibility of the depth profiling of multilayer targets are presented. The energy spectra of electrons normally incident on Nb/Si and Nb/Al/Nb/Si targets and reflected from them at an angle of 45° to the normal are taken. A method for the depth profiling of such structures is elaborated. 相似文献
19.
Peculiarities of Gaussian pulse reflection from a thin film with a resonance frequency dependence of the permittivity on a substrate with material parameters not depending on frequency are studied. Results of numerical analysis of equations determining the light field distribution in the reflected pulse are presented. The effect of the angle of incidence, carrier frequency, and duration of the incident pulse on the shift and transformation of the reflected pulse envelope is considered. 相似文献