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Full wave analysis of plane wave diffraction by a finite sinusoidal grating: E-polarization case
摘要： Plane wave diffraction studies of a finite sinusoidal grating have previously assumed that the grating length is large in wavelengths and the depth of its corrugations is small compared to a wavelength. This paper introduces a rigorous technique, the Method of Analytical Regularization (MAR), which removes these restrictions. The solution obtained by this method is free from limitations on the parameters of sinusoidal grating and possesses the capability to achieve predetermined accuracy of computations uniformly in a wide frequency band. The results of previous studies, which employed the Wiener-Hopf technique combined with a perturbation method, are compared with those obtained by the MAR; excellent concordance of results in the common parameter regimes of applicability of both methods is found. The different regimes of applicability of each approach are identified; within these, the MAR provides effective and efficient solutions to benchmark problems for testing other approximate techniques.
关键词： efficient computational algorithm in wide frequency band,scattering of E-polarized plane wave,method of analytical regularization,Floquet modes for finite grating,finite sinusoidal grating,Wiener-Hopf technique combined with perturbation method
更新于2025-09-23 15:23:52
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Handheld pocket-size Fourier transform profilometry using projector-enabled smartphone
摘要： Surface Fourier transform profilometry (FTP) is a technique used for reconstructing three-dimensional (3-D) surface topography using light. It has been widely used in machine vision for biomedical and biometric automations, providing solutions beyond conventional 2-D imaging. This paper proposes an implementation of the handheld pocket-size FTP for 3-D surface profile imaging using a projector-enabled Samsung Galaxy Beam smartphone. In the implementation, a crossed-optical-axes geometry of the FTP is formed by using a mirror positioned over the phone’s projector via an adjustable tilt mounting bracket. Experimental proof-of-concept of the proposed profilometry is done by implementing conventional and non-phase shifting FTPs with different diffuse test objects. The experimental results obtained by using the non-phase shifting technique are in good agreement with those of the direct contact measurement. Besides having superiority of compactness, the proposed profilometry paves the way for the development of real-time 3-D profiling and printing through internet or Bluetooth interconnection.
关键词： 3-D profilometry,non-phase shifting technique,contrast function,sinusoidal grating,projector-enabled smartphone,3-D surface topography,Samsung galaxy beam,Fourier transform,shape measurement
更新于2025-09-23 15:21:01
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Rectangular and sinusoidal Au-Grating as plasmonic sensor: A comparative study
摘要： Sensitivity of surface plasmon resonance sensor (SPRS) is mainly associated to efficient excitation of surface plasmon polaritons (SPPs) waves. In this work, effect of 50 nm thick Au film designed as rectangular and sinusoidal grating structure on glass substrate has been explored by finite element analysis (FEA) using COMSOL Multiphysics 5.3a. The comparison between the rectangular and sinusoidal gratings for efficient sensing has been presented here. Slit width (SW) for grating device has been optimized by applying far-field and near-field analysis while periodicity of grating structure is kept constant. Far field transmission spectra for both devices have been analyzed by illuminating the grating device through excitation port from the substrate side. Resonance wavelength (RW) dips for plasmonic grating device has been examined in each transmission spectrum for different values of refractive indices (RI). The sensitivity of plasmonic grating device has been calculated by measuring the shift in resonance wavelength by varying refractive index of analyte. The sinusoidal grating supporting fundamental plasmonic mode is found to be more sensitive (717 nm/RIU) as compared to simple rectangular grating (693 nm/RIU). Being highly sensitive to minute change in refractive index, such devices are efficiently applicable in real life.
关键词： Plasmonic sensor,Sinusoidal grating,Finite element analysis,Refractive index sensing,Sensitivity,Rectangular grating
更新于2025-09-11 14:15:04