共查询到20条相似文献,搜索用时 31 毫秒
1.
Haiyan Chen 《International Journal of Infrared and Millimeter Waves》2005,26(8):1141-1150
This paper addresses in the design of thin film filter for IR broadband integrated photonic amplifiers. A cascaded multilayer medium thin film filter structure is presented. This proposed filter consists of some different filtering unit cells with different central wavelength and bandwidth, and each cell can suppress certain peak gain at a specific wavelength. The intrinsical gain spectrum of amplifier is obtained by solving a set of rate and power propagation equations with finite difference time-domain(FDTD)-based overlapping integral-Runge Kutter(RK) method. The effect of transmittance spectrum of the proposed cascaded multilayer medium thin film filter on flattening gain is discussed. The transmission function of the cascaded multilayer medium thin film filter is obtained. Finally, a real device is fabricated, it is shown that the design is valid. 相似文献
2.
Lehman SK 《The Journal of the Acoustical Society of America》2005,117(5):2929-2936
Most diffraction tomography (DT) algorithms use a homogeneous Green function (GF) regardless of the medium being imaged. This choice is usually motivated by practical considerations: analytic inversions in standard geometries (Cartesian, spherical, etc.) are significantly simplified by the use of a homogeneous GF, estimating a nonhomogeneous GF can be very difficult, as can incorporating a nonhomogeneous GF into standard DT algorithms. Devaney has circumvented these issues by developing a purely numerical DT inversion algorithm [A. J. Devaney and M. Dennison, Inverse Probl. 19, 855-870 (2003)] that is independent of measurement system geometry, number of frequencies used in the reconstruction, and GF. A planar multilayer GF has been developed for use in Devaney's "Hilbert space" algorithm and used in a proof-of-principle nondestructive evaluation (NDE) experiment to image noninvasively a flaw in an aluminum/copper planar multilayer medium using data collected from an ultrasonic measurement system. The data were collected in a multistatic method with no beamforming: all focusing through the multilayer was performed mathematically "after-the-fact," that is, after the data were collected. 相似文献
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Peep Adamson 《Surface science》2006,600(3):735-742
The reflection of linearly polarized light from a multilayer system of ultrathin dielectric surface films is investigated both analytically in the long-wavelength limit and numerically by the standard way of calculating the reflection characteristics for the layered medium. The second-order approximate formulas for reflection coefficients and characteristic reflection angles are derived and their accuracy is estimated. It is shown that approximate expressions obtained for reflection parameters of multilayer system in the long-wavelength limit are of immediate interest to the solution of the inverse problem for ultrathin layered surface structures. Innovative possibilities for optical diagnostics are generated by means of polarizing and principal angles. For determining the parameters of multiple surface layers an appropriate method is found by combining differential reflectance with ellipsometry. 相似文献
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A write/read system using high-productivity multilayer optical discs was developed. The recording medium used in the system consists of planar recording layers and a separated guide layer, and is fabricated by web coating and lamination process. The recording layers in the medium are made of one-photon-absorption material, on which data can be recorded with a normal laser diode. The developed system is capable of focusing and tracking on the medium and amplifying readout signals by using phase-diversity homodyne detection. A highly layer-selective focusing method using homodyne detection was also proposed. This method obtains stable focus-error signals with clearly separated S-shaped curves even when layer spacing is quite narrow, causing large interlayer crosstalk. Writing on the medium and reading with the signal amplification effect of homodyne detection was demonstrated. In addition, the effectiveness of the method was experimentally evaluated. 相似文献
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A new method of the eigenvalue problem solution for a resonator with inhomogeneous active medium is given. The approach is based on Maxwell's wave equation and impedance boundary conditions of resonance-type at open resonator ends. A resonator equipped with mirrors in the form of infinite long strips is studied as an example. A rigorous solutions for the cases of stepped and bounded parabolic active medium profiles are obtained. Transcendental eigenvalue equations are investigated, distributions of field amplitude of active resonator modes are found. Asymptotic behavior of rigorous solutions is investigated. A multilayer approximation method is proposed for the eigenvalue problem solution for a resonator with an arbitrary gradient profile of active medium. The testing of this method was carried out with the rigorous solutions for the bounded parabolic profile. 相似文献
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Metal oxide thin films, suitable for use on solar
energy converters and photocatalitic applications, have been
characterized on-line by ellipsometric monitoring system. Ellipsometry
is a powerful and non-invasive technique of film analysis but it is
indirect tool. The most interesting parameters such as film thickness
and complex refractive indices can be determined only by computer sample
modelling. The complex reflection coefficients obtained from model
calculation were compared with ellipsometric measurements. We discuss
composition of multilayer film structure using various models and
fittings method. The implementation of effective medium approximation
procedure enables to interpret multilayer oxides structure formation
during passivation process. It is shown that an accurate model fitting
was obtained using Levenberg-Marquardt optimization algorithm and
multidimensional mean square error. 相似文献
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V. P. Afanas’ev D. S. Efremenko A. V. Lubenchenko 《Journal of Surface Investigation: X-ray, Synchrotron and Neutron Techniques》2013,7(2):285-289
The equations of light transfer in a turbid medium and transfer equations for electrons undergoing only elastic collisions in a solid body are shown to be equivalent. The angular distributions of elastically reflected electrons were calculated using the DISORT and MDOM optical codes. The calculation data are compared with the results of experimental measurements for the angular distributions of elastically reflected electrons and with calculations according to the Monte-Carlo method. Optical codes are shown to be highly efficient in calculating the angular distributions of electrons elastically reflected from multilayer media. 相似文献
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A. V. Filippov 《Journal of Experimental and Theoretical Physics》2016,122(4):716-721
The factors affecting the slope of the dispersion curve of the spin-wave resonance spectrum in multilayer films are determined. It is shown that an increase in the slope of the curve for the transverse orientation of the constant magnetic field relative to the film upon an increase in frequency is due to enhancement of dynamic as well as dissipative mechanisms of spin pinning. It is found that an increase in the damping parameter increases the degree of spin pinning in the case when the pinning layer is a reactive medium for spin oscillations and can decrease the degree of pinning when it is a dispersive medium. The conditions ensuring a higher degree of accuracy in determining the exchange interaction constant from the spin-wave resonance spectrum in multilayer films are determined. 相似文献
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V. I. Belotelov A. K. Zvezdin V. A. Kotov A. P. Pyatakov 《Physics of the Solid State》2003,45(10):1957-1965
Nongyrotropic magneto-optical effects are investigated in metal-insulator magnetic multilayer thin films. These effects manifest themselves in changes in the coefficients of transmission and reflection of electromagnetic radiation from the surface of a multilayer film due to the crossover of the magnetic structure from an antiferromagnetic configuration to a ferromagnetic configuration. The nongyrotropic magneto-optical effect observed in reflected light is analyzed theoretically. It is assumed that the multilayer structure is exposed to radiation of a monochromatic plane wave polarized along the direction of magnetization of the film. The magneto-optical effect is described in terms of the permittivity tensor of the multilayer medium, which depends only on the light frequency. The Boltzmann kinetic equation is treated with allowance made for spin-dependent electron scattering both inside conducting layers and at rough interfaces. Using an Fe/C multilayer as an example, it is demonstrated that the nongyrotropic magneto-optical effect is equal in order of magnitude to the equatorial Kerr effect or other strong magneto-optical effects. 相似文献
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S. A. Lysenko 《Optics and Spectroscopy》2018,124(1):129-139
A method for rapid calculation of a flux of stimulated fluorescence of a multilayer optically dense medium with inhomogeneous distribution of the fluorophore has been developed. The light field in the medium at the excitation wavelength of fluorescence is represented by a superposition of incident collimated, incident diffuse, and reflected diffuse fluxes. A two-stream approximation is used to describe the light field in the medium at the wavelength of emission of the fluorescence. Fluxes in adjacent elementary layers of the medium and on its surface are connected by simple matrix operators that are obtained using a combination of engineering approaches of radiation-transfer theory and single-scattering approximation. The calculations of fluorescence fluxes of a four-layer biotissue that are excited and recorded at 400–800 nm are compared with their Monte Carlo simulation with a discrepancy of 1%. The effect of the propagation medium on the fluorescence spectra of 5-ALA-induced protoporphyrin IX that are recorded from human skin was studied, and a technique for their correction that is based on measurements and quantitative analysis of the diffuse reflectance spectrum of skin was proposed. 相似文献
13.
Transformation acoustics are concentrated for the purpose of designing novel acoustic devices to tailor acoustic waves to achieve desirable characteristics. However, these devices require fluid or fluid-like materials with an anisotropic density that generally does not exist in nature. Therefore, we introduce pentamode metamaterials into an alternating multilayer isotropic medium model to build fluid-like metamaterials with an anisotropic density. A 2D acoustic bending based on transformation acoustics is established and investigated to verify our method. This idea provides a method to design broadband and physically realizable acoustic metamaterials with an anisotropic density and is meaningful for the design of acoustic metamaterials. 相似文献
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A. M. Zyuzin M. A. Bakulin V. V. Radaikin S. N. Sabaev N. V. Yantsen 《Bulletin of the Russian Academy of Sciences: Physics》2010,74(10):1431-1433
It is shown that effective spin pinning in a multilayer can be provided by both the layer that is in the state of reactive
(elastic) medium and (at a sufficiently large difference in the uniform-resonance fields) by the layer serving a dispersive
medium for spin waves. 相似文献
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提出了将冰层进行多孔介质等效方法,对冰层、液体/波导层/压电基底多层乐甫(Love)波导结构建立分层介质模型,利用部分波理论和边界条件精确推导,分析不同状态下的传感响应,求解结冰过程Love波速度及声波衰减的变化,获得结冰过程中的声学传感机制。为了验证理论分析,实验制作了200 MHz的36°LiTaO3/SiO2波导结构的Love波器件,并构建模拟环境的试验系统对研制器件进行了实验测试。实验结果表明,利用Love波的工作频率以及插入损耗瞬变这一特征可以实现对结冰状态的准确监测。 相似文献
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实际应用中的薄膜或多或少存在体折射率不均匀缺陷,其准确表征对于镀膜工艺参数调校、低损耗薄膜设计与制备分析等具有影响。从Schr-der近似出发,推导了体折射率弱不均匀薄膜的膜系特征矩阵,通过特征矩阵法推广,建立了体折射率弱不均匀多层膜光谱特性计算的近似模型。利用基于有效介质理论的多层均匀膜近似方法,讨论了上述近似模型的有效性、计算精度和时间消耗特性。结果表明,上述模型矩阵计算中引入体折射不均匀度这一参数,为多层膜体折射率不均匀缺陷反演提供了一种有效的手段,为基于宽带光谱测量数据拟合的膜层缺陷数值反演应用奠定了基础。 相似文献
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