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1
Pechprasarn, Suejit, Acharawan Panlomso, Suttipong Aiam-Um, Phitsini Suvarnaphaet, Sani Boonyagul, Michael G. Somekh, and Naphat Albutt. "Rigorous Coupled Wave Analysis for Plasmonic Nanoparticles." Applied Mechanics and Materials 866 (June 2017): 341–44. http://dx.doi.org/10.4028/www.scientific.net/amm.866.341.
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Electromagnetic simulation packages for nanoparticles have become of interest for science and engineering community because of interesting properties of nanomaterials, such as, plasmonics and localized field enhancement. There are several approaches to calculate electromagnetic wave responses including time domain and frequency domain; each approach does have its own pros and cons. In this paper, we discuss basic principle of Rigorous coupled wave analysis (RCWA) and some key issues of 2D Rigorous Coupled Wave Analysis (RCWA) for nanoparticle simulation, such as, the computing demands (long computation time and memory consumption) and staircase approximation. We also suggest some feasible approaches to get around the issues and speed up the calculation, such as, employing Li Feng Li’s RCWA algorithm for circular and elliptical rods, making use of the symmetry of spherical shape particles to reduce redundancies in computation and building up an Eigenvector/Eigenvalue database of difference radii of disks, so that these disks can be stacked together to form various sizes of nanospheres.
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Kazanskiy, N. L., and P. G. Serafimovich. "Cloud Computing for Rigorous Coupled-Wave Analysis." Advances in Optical Technologies 2012 (July 2, 2012): 1–7. http://dx.doi.org/10.1155/2012/398341.
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Design and analysis of complex nanophotonic and nanoelectronic structures require significant computing resources. Cloud computing infrastructure allows distributed parallel applications to achieve greater scalability and fault tolerance. The problems of effective use of high-performance computing systems for modeling and simulation of subwavelength diffraction gratings are considered. Rigorous coupled-wave analysis (RCWA) is adapted to cloud computing environment. In order to accomplish this, data flow of the RCWA is analyzed and CPU-intensive operations are converted to data-intensive operations. The generated data sets are structured in accordance with the requirements of MapReduce technology.
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Chen, De Wei. "Rigorous Coupled Wave Analysis of Surface Plasmon Resonance Sensor Based on Metallic Grating." Advanced Materials Research 211-212 (February 2011): 465–68. http://dx.doi.org/10.4028/www.scientific.net/amr.211-212.465.
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Since the development almost a decade ago of the first biosensor based on surface plasmon resonance (SPR), the use of this technique has increased steadily. In this study, we theoretically investigated the sensing character of SPR sensor with reflection type metallic with Rigorous Coupled Wave Analysis (RCWA) method, and the mechanism is analyzed by the field distribution. It is found that the sensitivity of negative diffraction order, which goes higher quickly as the resonant angle increases, is much greater than that of positive diffraction order.
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Gou, Jun, Hilal Cansizoglu, Cesar Bartolo-Perez, Soroush Ghandiparsi, Ahmed S. Mayet, Hossein Rabiee-Golgir, Yang Gao, et al. "Rigorous coupled-wave analysis of absorption enhancement in vertically illuminated silicon photodiodes with photon-trapping hole arrays." Nanophotonics 8, no. 10 (September 25, 2019): 1747–56. http://dx.doi.org/10.1515/nanoph-2019-0164.
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AbstractIn this paper, we present a rigorous coupled-wave analysis (RCWA) of absorption enhancement in all-silicon (Si) photodiodes with integrated hole arrays of different shapes and dimensions. The RCWA method is used to analyze the light propagation and trapping in the photodiodes on both Si-on-insulator (SOI) and bulk Si substrates for the datacom wavelength at about 850 nm. Our calculation and measurement results show that funnel-shaped holes with tapered sidewalls lead to low back-reflection. A beam of light undergoes a deflection subsequent to the diffraction in the hole array and generates laterally propagating waves. SOI substrates with oxide layers play an important role in reducing the transmission loss, especially for deflected light with higher-order diffraction from the hole array. Owing to laterally propagating modes and back-reflection on the SiO2 film, light is more confined in the thin Si layer on the SOI substrates compared to that on the bulk Si substrates. Experimental results based on fabricated devices support the predictions of the RCWA. Devices are designed with a 2-μm-thick intrinsic layer, which ensures ultrafast impulse response (full-width at half-maximum) of 30 ps. Measurements for integrated photodiodes with funnel-shaped holes indicate an enhanced external quantum efficiency of more than 55% on the SOI substrates. This represents more than 500% improvement compared to photodiodes without integrated phototrapping nanoholes.
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Jin, Xiao Min, Douglas Alan Cattarusa, and Michael James Marshall. "Study of Top Triangular Nano-Grating on Solar Cell Using Rigorous Coupled Wave Analysis." Advanced Materials Research 571 (September 2012): 427–32. http://dx.doi.org/10.4028/www.scientific.net/amr.571.427.
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This paper presents the simulation results of top nano-grating on solar cell using rigorous coupled wave analysis (RCWA) method. However, compared to other simulation results, we calculated weighted total transmission of solar cell according to Sun spectrum and Silicon photo detector responsivity. Our optimization shows that the top grating with period 200nm, width 40nm, and height 150nm is the optimization structure. This case has 0.45544 total weighted transmission powers and is about 70.9% improvement compared to the non-grating case.
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Lokar, Ziga, Benjamin Lipovsek, Marko Topic, and Janez Krc. "Performance analysis of rigorous coupled-wave analysis and its integration in a coupled modeling approach for optical simulation of complete heterojunction silicon solar cells." Beilstein Journal of Nanotechnology 9 (August 28, 2018): 2315–29. http://dx.doi.org/10.3762/bjnano.9.216.
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A variety of light management structures have been introduced in solar cells to improve light harvesting and further boost their conversion efficiency. Reliable and accurate simulation tools are required to design and optimize the individual structures and complete devices. In the first part of this paper, we analyze the performance of rigorous coupled-wave analysis (RCWA) for accurate three-dimensional optical simulation of solar cells, in particular heterojunction silicon (HJ Si) solar cells. The structure of HJ Si solar cells consists of thin and thick layers, and additionally, micro- and nano-textures are also introduced to further exploit the potential of light trapping. The RCWA was tested on the front substructure of the solar cell, including the texture, thin passivation and contact layers. Inverted pyramidal textures of different sizes were included in the simulations. The simulations rapidly converge as long as the textures are small (in the (sub)micrometer range), while for larger microscale textures (feature sizes of a few micrometers), this is not the case. Small textures were optimized to decrease the reflectance, and consequently, increase the absorption in the active layers of the solar cell. Decreasing the flat parts of the texture was shown to improve performance. For simulations of structures with microtextures, and for simulations of complete HJ Si cells, we propose a coupled modeling approach (CMA), where the RCWA is coupled with raytracing and the transfer matrix method. By means of CMA and nanotexture optimization, we show the possible benefits of nanotextures at the front interface of HJ Si solar cells, demonstrating a 13.4% improvement in the short-circuit current density with respect to the flat cell and 1.4% with respect to the cell with double-sided random micropyramids. We additionally demonstrate the ability to simulate a combination of nano- and microtextures at a single interface, although the considered structure did not show an improvement over the pyramidal textures.
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Su, Wei, Gai Ge Zheng, and Xiang Yin Li. "Photonic Crystal Biosensor Using Surface Plasmon Resonance Effect." Advanced Materials Research 669 (March 2013): 246–49. http://dx.doi.org/10.4028/www.scientific.net/amr.669.246.
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We have proposed a biosensor using a one-dimensional (1D) photonic crystal with surface plasmon resonance (SPR) effect. The wavelength interrogation method has been used to study the performance of the sensor. Numerical simulations based on rigorous coupled wave analysis (RCWA) method show that the sensitivity of the optimized sensor is 137 nm/RIU (per refractive index unit).
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Cai, Er Fei, Yong Qing Huang, Xiao Feng Duan, and Xiao Min Ren. "Design and Analysis of Optical-Communication-Band Sub-Wavelength Grating Polarizer." Advanced Materials Research 683 (April 2013): 207–10. http://dx.doi.org/10.4028/www.scientific.net/amr.683.207.
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According to the requirement of the optical communication devices, sub-wavelength grating polarizer was studied based on rigorous coupled-wave analysis (RCWA) and designed with SOI materials. The paper analyzes the grating parameters such as the period, depth, fill groove that influence the diffraction efficiency of the grating. The TM mode diffraction efficiency is more than 95%, and the TE mode diffraction efficiency is less than 5%, the pyramidal sub-wavelength polarizer grating has good polarizer performance than others shapes in the optical communication band of 1550nm. In this paper, we designed this kind of sub-wavelength grating polarizer has great potential applying in optical switching, optical memory, optical detectors and other photo-electronic devices.
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David, Christin. "TiO2 Self-Assembled, Thin-Walled Nanotube Arrays for Photonic Applications." Materials 12, no. 8 (April 24, 2019): 1332. http://dx.doi.org/10.3390/ma12081332.
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Two-dimensional arrays of hollow nanotubes made of TiO 2 are a promising platform for sensing, spectroscopy and light harvesting applications. Their straightforward fabrication via electrochemical anodization, growing nanotube pillars of finite length from a Ti foil, allows precise tailoring of geometry and, thus, material properties. We theoretically investigate these photonic crystal structures with respect to reduction of front surface reflection, achievable field enhancement, and photonic bands. Employing the Rigorous Coupled Wave Analysis (RCWA), we study the optical response of photonic crystals made of thin-walled nanotubes relative to their bare Ti foil substrate, including under additional charge carrier doping which might occur during the growth process.
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Zhu, Wenhua, Bo Wang, Chenhao Gao, Kunhua Wen, Ziming Meng, Zhaogang Nie, Qu Wang, et al. "Research on reflective three-output by packaged grating under second Bragg angle." Modern Physics Letters B 33, no. 25 (September 10, 2019): 1950305. http://dx.doi.org/10.1142/s0217984919503056.
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This paper designed a novel three-output reflective packaged grating. The optimized parameters such as the period and depth of the high-efficiency three-output grating with an incident wavelength of 1550 nm can be calculated by rigorous coupled-wave analysis (RCWA). According to the optimized result, the grating can diffract the incident light energy into three orders with an efficiency of nearly 33% under the premise of second Bragg angle incidence and the given duty ratio of 0.5. The diffraction efficiency of the packaged grating is improved compared to the surface-relief three-output grating under second Bragg angle incidence, especially for TE-polarized light.
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Lee, Chih Kung, C. L. Lin, D. Z. Lin, T. D. Cheng, Ching Kao Chang, L. B. Yu, and C. S. Yeh. "Developing a Nanowriter System: Simulation and Experimental Set-Up of a Plasmonic-Based Lens Design." Materials Science Forum 505-507 (January 2006): 1–6. http://dx.doi.org/10.4028/www.scientific.net/msf.505-507.1.
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The aim of this article is to introduce a nanowriter system that could lead to a sub-micrometer spot size using a visible light source under ambient conditions. The key component of the system is a focusing optical head, which incorporates a plasmonic-based lens instead of a conventional lens. Based on knowledge of the physical origin of extraordinary transmission and directional beaming, we theorize that the directional beaming phenomenon can be explained simply as a surface plasmon (SP) diffraction along the corrugations as long as the multiple scattering effects are taken into account to modify the dispersion relationship of the surface plasmon. We introduce a Rigorous Coupled Wave Analysis (RCWA) formulation to pursue a precise dispersion relationship needed for the lens design. Comparing the resultant theoretical data between Finite Difference Time Domain (FDTD) simulations and RCWA results, we found good agreement and the many important characteristic parameters needed for an innovative lens design. We also set up a writing-test optomechanical system to examine the photoresist exposure ability of the plasmonic-based lens.
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Kim, Sung Chul. "Simulation of Rough Surface of CIGS (CuInGaSe) Solar Cell by RCWA (Rigorous Coupled Wave Analysis) Considering the Incoherency of Light." Journal of the Optical Society of Korea 18, no. 2 (April 25, 2014): 180–83. http://dx.doi.org/10.3807/josk.2014.18.2.180.
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Gao, Yang, Qi Xia, Guang Lan Liao, and Tie Lin Shi. "Sensitivity Analysis of a Bioinspired Refractive Index Based Gas Sensor." Advanced Materials Research 268-270 (July 2011): 235–40. http://dx.doi.org/10.4028/www.scientific.net/amr.268-270.235.
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Nano-structures on the wing of Morpho butterflies generate bright blue color, and this color is sensitive to ambient gas, or more specifically, the refractive index of ambient gas. It was found that even slight change of the refractive index can lead to obvious change of the color. Such phenomenon has caught much attention and was employed as a sensing principle for detecting gas. In the present study, a typical nano-structure on the wing of Morpho butterflies is mimicked and simplified for constructing a refractive index based gas sensor. Moreover, partial derivative of the optical reflection efficiency with respect to the refractive index of ambient gas, i.e., sensitivity of the sensor, is utilized based on the rigorous coupled-wave analysis (RCWA) method. Finally, the effects of the nano-structure’s shape on the partial derivative are analyzed. The results can be applied to the design of the bioinspired refractive index based gas sensor.
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Xiong, Xue Hui, La Min Zhan, and Xuan Ke. "Effects of Grating Slant Angle on Surface Plasmon Resonance and its Applications for Sensors." Applied Mechanics and Materials 536-537 (April 2014): 342–45. http://dx.doi.org/10.4028/www.scientific.net/amm.536-537.342.
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In this study, we emphasized on effects of grating slant angle of tilted dielectric gratings (TG) on surface plasmon resonance (SPR). The momentum conservation for an optical wave exciting an SPR via TG is different from unslant gratings. The coupling condition induces the period along the grating surface (in the direction x) be decided not only by grating period but also by slant angle. The results calculated by rigorous coupled-wave analysis theory (RCWA) indicate that the resonant wavelength and the refractive index sensitivity are strongly dependent on the period in the direction x (noted Λx). And the refractive index sensitivity increases with the rise of the period Λx. The SPR sensor through TG offers high sensitivity about 800nm per refractive index unit and narrow full-width at half maximum (FWHM) about 5nm when monitoring biochemical liquid solutions.
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Bošnjaković, Dejan, Nerea Sebastián, and Irena Drevenšek-Olenik. "Magnetically Tunable Liquid Crystal-Based Optical Diffraction Gratings." Polymers 12, no. 10 (October 14, 2020): 2355. http://dx.doi.org/10.3390/polym12102355.
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We present a theoretical analysis of optical diffractive properties of magnetically tunable optical transmission gratings composed of periodically assembled layers of a polymer and a ferromagnetic liquid crystal (LC). The orientational structure of the LC layers as a function of an applied magnetic field is calculated by minimization of the Landau-de Gennes free energy for ferromagnetic LCs, which is performed numerically and also analytically by using the one-constant approximation and the approximations of the high and the low magnetic fields. Optical diffractive properties of the associated diffraction structure are calculated numerically in the framework of rigorous coupled-wave analysis (RCWA). The presented methodology provides a basis for designing new types of diffractive optical element based on ferromagnetic LCs and simulating their operation governed by the in-plane magnetic field.
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Li, Hongtao, Bo Wang, Hao Pei, Wenhao Shu, Li Chen, Liang Lei, and Jinyun Zhou. "Reflective three-port high-efficiency grating with two dielectric layers based on a sandwiched configuration." International Journal of Modern Physics B 30, no. 12 (May 6, 2016): 1650072. http://dx.doi.org/10.1142/s0217979216500727.
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In this paper, we describe a novel reflective sandwiched three-port grating with two dielectric layers. The two-layer sandwiched grating can separate incident wave into the [Formula: see text] and the 0th-order with high-efficiency beam splitting and good splitting ratios for both transverse electric (TE) and transverse magnetic (TM) polarizations. The grating parameters can be optimized by using rigorous coupled-wave analysis (RCWA) with a special duty cycle of 0.6. With the optimized results, efficiencies more than 32% in the [Formula: see text]st-orders and the 0th-order can be obtained. Furthermore, performance of the incident bandwidth and aspect ratio can be improved. Compared with conventional surface-relief grating, the grating with sandwiched structure is aimed at cleaning and protecting grating surface. The presented reflective two-layer sandwiched three-port grating would be put into practical applications for its beneficial performances.
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Shao, Ren Jin, Yan Ye, Xiao Xuan Dong, Yun Zhou, Su Shen, and Lin Sen Chen. "Color Filters Based on the Subwavelength Triangular-Lattice Cylinder Arrays in Metal-Dielectric Films." Key Engineering Materials 562-565 (July 2013): 737–43. http://dx.doi.org/10.4028/www.scientific.net/kem.562-565.737.
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Abstract: Color filter incorporating a subwavelength triangular-lattice cylinder arrays in metal-dielectric films on quartz substrate was proposed. The device consists of a quartz substrate, a triangular-lattice cylinder arrays in both dielectric layer of ZnS and a metallic layer of aluminum (Al). The broadband transmission characteristic of the proposed device in the visible wavelength range was investigated in detail by the rigorous coupled wave analysis (RCWA). Specially by discussing the effects of the structure parameters to the resonant wavelength, typical optimized structure parameters are obtained, in which more than 74.6% peak transmission efficiency with FWHM of ~ 80 nm were simultaneously achieved for the tricolor filters. The simulation results show that the peak transmission efficiency (PET) increases more than 17% with lower color cross-talk compared to the previous color filters.
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Tao, Zilong, Jun Zhang, Jie You, Hao Hao, Hao Ouyang, Qiuquan Yan, Shiyin Du, et al. "Exploiting deep learning network in optical chirality tuning and manipulation of diffractive chiral metamaterials." Nanophotonics 9, no. 9 (June 16, 2020): 2945–56. http://dx.doi.org/10.1515/nanoph-2020-0194.
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AbstractDeep-learning (DL) network has emerged as an important prototyping technology for the advancements of big data analytics, intelligent systems, biochemistry, physics, and nanoscience. Here, we used a DL model whose key algorithm relies on deep neural network to efficiently predict circular dichroism (CD) response in higher-order diffracted beams of two-dimensional chiral metamaterials with different parameters. To facilitate the training process of DL network in predicting chiroptical response, the traditional rigorous coupled wave analysis (RCWA) method is utilized. Notably, these T-like shaped chiral metamaterials all exhibit the strongest CD response in the third-order diffracted beams whose intensities are the smallest, when comparing up to four diffraction orders. Our comprehensive results reveal that by means of DL network, the complex and nonintuitive relations between T-like metamaterials with different chiral parameters (i. e., unit period, width, bridge length, and separation length) and their CD performances are acquired, which owns an ultrafast computational speed that is four orders of magnitude faster than RCWA and a high accuracy. The insights gained from this study may be of assistance to the applications of DL network in investigating different optical chirality in low-dimensional metamaterials and expediting the design and optimization processes for hyper-sensitive ultrathin devices and systems.
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Gao, Xu Min, Zheng Shi, Xin Li, Shu Min He, Hong Bo Zhu, and Yong Jin Wang. "An Electromechanical Tunable Grating on Silicon-on-Insulator Platform." Key Engineering Materials 609-610 (April 2014): 1277–82. http://dx.doi.org/10.4028/www.scientific.net/kem.609-610.1277.
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We report here the design and fabrication of an electromechanical tunable grating on silicon-on-insulator (SOI) wafer. The tunable grating consists of a submicron electrostatic comb actuator and an expandable freestanding grating. Rigorous coupled-wave analysis (RCWA) method is utilized to analyze the optical responses of freestanding grating with different periods and filling factors. Obvious shift of the resonant peaks is obtained by changing the grating period and the grating filling factor. The electromechanical tunable grating is realized on the silicon device layer by a combination of electron beam (EB) lithography, deep reactive ion etching (DRIE) and wet etching. Scanning electron microscope (SEM) micrographs indicate that the grating is well fabricated. Via applying biased voltage, the force generated by the electrostatic comb actuator can modulate periods and filling factors of the freestanding grating. The electromechanical tunable grating with simple fabrication process shows bright prospects for optical telecoms and miniaturized spectrometers.
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Fitio, Volodymyr, Iryna Yaremchuk, Andriy Bendziak, Michal Marchewka, and Yaroslav Bobitski. "Diffraction of a Gaussian Beam with Limited cross Section by a Volume Phase Grating under Waveguide Mode Resonance." Materials 14, no. 9 (April 27, 2021): 2252. http://dx.doi.org/10.3390/ma14092252.
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In this work, the diffraction of a Gaussian beam on a volume phase grating was researched theoretically and numerically. The proposed method is based on rigorous coupled-wave analysis (RCWA) and Fourier transform. The Gaussian beam is decomposed into plane waves using the Fourier transform. The number of plane waves is determined using the sampling theorem. The complex reflected and transmitted amplitudes are calculated for each RCWA plane wave. The distribution of the fields along the grating for the reflected and transmitted waves is determined using inverse Fourier transform. The powers of the reflected and transmitted waves are determined based on these distributions. Our method shows that the energy conservation law is satisfied for the phase grating. That is, the power of the incident Gaussian beam is equal to the sum of the powers of the reflected and transmitted beams. It is demonstration of our approach correctness. The numerous studies have shown that the spatial shapes of the reflected and transmitted beams differ from the Gaussian beam under resonance. In additional, the waveguide mode appears also in the grating. The spatial forms of the reflected and transmitted beams are Gaussian in the absence of resonance. It was found that the width of the resonance curves is wider for the Gaussian beam than for the plane wave. However, the spectral and angular sensitivities are the same as for the plane wave. The resonant wavelengths are slightly different for the plane wave and the Gaussian beam. Numerical calculations for four refractive index modulation coefficients of the grating medium were carried out by the proposed method. The widths of the resonance curves decrease with the increasing in the refractive index modulation. Moreover, the reflection coefficient also increases.
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Bošnjaković, Dejan, Mathias Fleisch, Xinzheng Zhang, and Irena Drevenšek-Olenik. "Electrically Tuneable Optical Diffraction Gratings Based on a Polymer Scaffold Filled with a Nematic Liquid Crystal." Polymers 13, no. 14 (July 13, 2021): 2292. http://dx.doi.org/10.3390/polym13142292.
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We present an experimental and theoretical investigation of the optical diffractive properties of electrically tuneable optical transmission gratings assembled as stacks of periodic slices from a conventional nematic liquid crystal (E7) and a standard photoresist polymer (SU-8). The external electric field causes a twist-type reorientation of the LC molecules toward a perpendicular direction with respect to initial orientation. The associated field-induced modification of the director field is determined numerically and analytically by minimization of the Landau–de Gennes free energy. The optical diffraction properties of the associated periodically modulated structure are calculated numerically on the basis of rigorous coupled-wave analysis (RCWA). A comparison of experimental and theoretical results suggests that polymer slices provoke planar surface anchoring of the LC molecules with the inhomogeneous surface anchoring energy varying in the range 5–20 μJ/m2. The investigated structures provide a versatile approach to fabricating LC-polymer-based electrically tuneable diffractive optical elements (DOEs).
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Ghmari, Faouzi, and Ilhem Mezni. "Study of the Absorptance of Si-gratings and of arrays of SiO2-filled trenches on Si-grating substrate." JOURNAL OF ADVANCES IN PHYSICS 12, no. 2 (August 30, 2016): 4278–90. http://dx.doi.org/10.24297/jap.v12i2.161.
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The purpose of this paper is to study the radiative properties of two model structures. The first model (A-1) is a rectangular grating of silicon (Si). The second one (A-2) is obtained from A-1 by filling their trenches by SiO2. These patterned wafers are characterized by three geometrical parameters, the period d, the filling factorand the thickness h. To derive and compute the radiative properties we use a rigorous coupled wave analysis (RCWA) method. Our attention is focused on the absorptance of these structures when they are illuminated by a monochromatic plane wave. We investigate the effect of the filling factor on the absorptance versus the direction of the incident wave. At specific angles of incidence the effect of the period is also studied. Besides, the influence of the thickness h on the absorptance is included throughout this work. At the wavelength = 632,8nm, we especially show that we can identify several perfect absorber model structures characterized by specific parameters and by accurate angle of incidence. We show that this will be done in both transverse electric (TE) and transverse magnetic (TM) polarization cases.
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Lee, ChaBum. "Total Internal Reflection-Based High Efficiency Grating Design for a Metal-Free Polarizing Filter Applications Using Hybrid Optimization Procedure." Advances in Optical Technologies 2014 (February 10, 2014): 1–7. http://dx.doi.org/10.1155/2014/393010.
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This paper presents a fast and rigorous design method for grating-based metal-free polarizing filter applications using two-step hybrid optimization techniques. Grating structures utilizing the total internal reflection in a lamellar configuration were used to achieve metal-free solution, which is a key technology in the chirped pulse amplification for high power laser system. Here two polarizing filters were designed: polarization sensitive and polarization insensitive. Those polarization performances were characterized by the rigorous coupled-wave analysis (RCWA), and the design parameters of grating structures, pitch, depth, and filling factor were optimized by two-step hybrid optimization procedure because the diffraction characteristics of grating-based polarizing filters are highly sensitive to small changes in design parameters. The Taguchi method is incorporated into selection process in the genetic algorithm, which indicates that the Taguchi method optimizes the design parameters in a coarse manner, and then, coarsely optimized parameters are finely optimized using the genetic algorithm. Therefore the proposed method could solve global numerical optimization problems with continuous variables. The proposed two-step hybrid optimization algorithm could effectively optimize the grating structures for the purpose of polarization filter applications, and the optimized grating structures could selectively filter the incident light up to 99.8% as to TE or TM waves.
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Zhou, Zhiguang, Enas Sakr, Omar Yehia, Anubha Mathur, and Peter Bermel. "Photonic Crystal Selective Structures for Solar Thermophotovoltaics." MRS Advances 1, no. 59 (December 21, 2015): 3883–89. http://dx.doi.org/10.1557/adv.2015.25.
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ABSTRACTSolar thermophotovoltaic (STPV) systems convert sunlight into electricity via thermal radiation. The efficiency of this process depends critically on both the selective absorber and the selective emitter, which are controlled by both the materials and the photonic design. For high concentration solar TPV applications, 2D photonic crystals (PhCs) made of refractory metals such as tungsten have demonstrated promising results. For even higher performance, we propose two photonic crystal-based designs to both collect solar heat and reradiate above-gap photons. First, a PhC selective structure (IPSS), which combines 2D photonic crystals and filters into a single device. Second, an Er-Yb-Tm co-doped fused silica coated with a 17-bilayer structure also offers significant selectivity with greater ease of fabrication. Finite difference time domain (FDTD) and rigorous coupled wave analysis (RCWA) simulations show that both can significantly suppress sub-bandgap photons. This increases sunlight-to-electricity conversion for photonic crystal-based emitters above 24.3% at 100 suns concentration or 27% at 1000 suns concentration using a Ga0.42In0.58As PV diode with a bandgap of 0.7 eV (nearly lattice-matched to InP).
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Gong, Bowen, and Huiying Wen. "Enhanced polarization-independent two-layer five-port grating with covering layer." Modern Physics Letters B 35, no. 25 (August 3, 2021): 2150348. http://dx.doi.org/10.1142/s0217984921503486.
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In this paper, an enhanced polarization-independent two-layer five-port grating with covering layer is proposed. The rigorous coupled-wave analysis (RCWA) is used to predict grating parameters. In addition, the total efficiency of the polarization-independent five-port grating with covering layer can exceed 80% with the good uniformity of 1.97% for TE and TM polarization. The inherent coupling mechanism and the electric field energy distribution of the gratings are explained well under TE and TM polarization by the simplified mode method (SMM) and the finite element method (FEM). According to the reported five-port gratings, the proposed transmission five-port grating with a covering layer has good uniformity for TE and TM polarization. Moreover, the grating can be protected and the groove of the grating can be kept clean by adding a covering layer during the actual fabrication. At the same time, the fabrication errors of the two-layer five-port diffraction grating are further considered. Therefore, the numerically simulated five-port grating with covering layer has a wide application prospect in precision displacement measurement and holographic projection imaging.
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Ying, Yu, Jiakai Wang, Nan Hu, Ke Xu, Liangliang Sun, and Guangyuan Si. "Determination of refractive index using surface plasmon resonance (SPR) and rigorous coupled wave analysis (RCWA) with a D-shaped optical fiber and a nano-gold grating." Instrumentation Science & Technology 48, no. 4 (February 19, 2020): 376–85. http://dx.doi.org/10.1080/10739149.2020.1728694.
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Jiang, Hao, Zhao Ma, Honggang Gu, Xiuguo Chen, and Shiyuan Liu. "Characterization of Volume Gratings Based on Distributed Dielectric Constant Model Using Mueller Matrix Ellipsometry." Applied Sciences 9, no. 4 (February 18, 2019): 698. http://dx.doi.org/10.3390/app9040698.
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Volume grating is a key optical component due to its comprehensive applications. Other than the common grating structures, volume grating is essentially a predesigned refractive index distribution recorded in materials, which raises the challenges of metrology. Although we have demonstrated the potential application of ellipsometry for volume grating characterization, it has been limited due to the absence of general forward model reflecting the refractive index distribution. Herein, we introduced a distributed dielectric constant based rigorous coupled-wave analysis (RCWA) model to interpret the interaction between the incident light and volume grating, with which the Mueller matrix can be calculated. Combining with a regression analysis with the objective to match the measured Mueller matrices with minimum mean square error (MSE), the parameters of the dielectric constant distribution function can be determined. The proposed method has been demonstrated using a series of simulations of measuring the volume gratings with different dielectric constant distribution functions. Further demonstration has been carried out by experimental measurements on volume holographic gratings recorded in the composite of polymer and zinc sulfide (ZnS) nanoparticles. By directly fitting the spatiotemporal concentration of the nanoparticles, the diffusion coefficient has been further evaluated, which is consistent to the result reported in our previous investigations.
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Cao, Bing, Gui Ju Zhang, Qin Han, Chin Hua Wang, Jian Feng Wang, and Ke Xu. "High Polaried Transmission Effects for Double-Layer Metallic Grating Films on GaN Substrate." Advanced Materials Research 295-297 (July 2011): 1289–93. http://dx.doi.org/10.4028/www.scientific.net/amr.295-297.1289.
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Highly polarized light transmission from GaN based light emitting diode is proposed using a double-layer metallic grating film and a dielectric transition layer. TM mode transmission and the polarized extinction ratio (ER) are calculated using commercial software, based on a full vector implementation of Rigorous Coupled Wave Analysis (RCWA) algorithm. Such a thin-film double-layer grating with subwavelength metallic stripes are designed and simulated by perfect parameters of period, thickness and filling factor for achieving good polarization properties. It is found that TM transmission and ER are almost stable and flat under different slit arrays of the double-layer grating. The polarized structure shows larger width of incident wavelength with a transition layer of a low refractive index than that of a high refractive index, but higher TM transmission and ER can be obtained for low refractive index transition layer. Flat sensitivity and high transmission of the TM mode on the double-layer metal grating thickness have been achieved. Up to 100nm range of the grating height can be employed to achieve TM transmission more than 92% while ER> 20dB. The results provide guidance in designing, optimizing and fabricating the integrated GaN-based and polarized photonic devices.
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Sakai, Daisuke, Hiroshi Kakiuchida, Kenji Harada, Jun Nishikawa, and Euichi Hirose. "Parallel plications may enhance surface function: physical properties of transparent tunics in colonial ascidians Clavelina cyclus and C. obesa." Journal of the Marine Biological Association of the United Kingdom 99, no. 8 (October 15, 2019): 1831–39. http://dx.doi.org/10.1017/s0025315419000833.
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AbstractAn array of nano-scale protrusions, called the nipple array, is found on the body surface of various invertebrates, and this structure is believed to decrease light reflectance and water wettability on the surface in the terrestrial environment. However, its potential functions have not been well studied in aquatic environments. Clavelina spp. are colonial ascidians that have the nipple array on their integumentary matrix (i.e. tunic). We examined the physical properties on the surface of the tunic of C. cyclus and C. obesa, such as hardness, wettability and refractive indices, to evaluate the functional importance of this structure. The tunic cuticle of both species was covered with the nipple array, and the cuticle of C. cyclus was bent into folds forming parallel plications. The Clavelina tunic was very soft and had high bubble- and oil-repellency. The refractive-index deviation between the tunic and seawater was 0.07–0.095 for 589-nm light (D-line). Rigorous coupled wave analysis (RCWA) showed that the nipple array slightly reduced reflectance on the surface and the parallel plications reduced the reflectance still more. The nanoimprinted plates imitating the parallel plications have higher bubble repellency and lower reflectance than the flat plates. These findings support the functional importance of the plications as well as the nipple array.
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Cao, Bing, Gui Ju Zhang, Chin Hua Wang, Jian Feng Wang, and Ke Xu. "Narrowband Notch Filters with Composite Nanostructure Layers on a GaN-Based Light Emitting Diode." Advanced Materials Research 486 (March 2012): 114–18. http://dx.doi.org/10.4028/www.scientific.net/amr.486.114.
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In this paper, novel active narrowband notch filters with triple-layer composite nanostructures on a GaN-based LED are obtained by mainly adjusting the grating period and duty cycle. The three layers consist of two dielectric thin layers and one metallic / dielectric grating layer. The grating layer composes of subwavelength period and thickness rectangular stripes, which lies between a transition layer and a protecting layer. Line-width and attenuation peak properties of the resonance filters are calculated and investigated by using a full vector implementation of Rigorous Coupled Wave Analysis (RCWA) algorithm. It is shown that the grating period can significantly change the filter peak wavelength, and the grating duty cycle heavily changes the filter line-width. The filter attenuation peak has a red shift with 23.3nm as the grating period increases 18nm. The FWHM (Full Width at Half Maximum) of the filter reduces from 1.9nm to 0.28nm as the duty cycle changes from 0.55 to 0.3, which compressed more than six times. Moreover, thickness of each composite nanostructure layer can also affect the narrowband width and peak wavelength of the filter. The results provide guidance in designing, optimizing and fabricating such an active narrowband filter with highly integrated photonic devices.
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Yang, Guanghua, Jing Li, Yu Wang, Minxia Ding, and Lina Zhong. "Analytic Design of Segmented Phase Grating for Optical Sensing in High-Precision Alignment System." Sensors 21, no. 11 (May 31, 2021): 3805. http://dx.doi.org/10.3390/s21113805.
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Ultra-precision measurement systems are important for semiconductor manufacturing processes. In a phase grating sensing alignment (PGA) system, the measurement accuracy largely depends on the intensity of the diffraction signal and its signal-to-noise ratio (SNR), both of which are associated with the grating structure. Although an equally segmented grating structure could increase the signal of a high odd order, it could also strengthen the signals at the zeroth and even orders which are the main contributors of stray light. This paper focuses on the practical problem of differently responding diffraction orders but in one grating structure. An analytical relationship has been established between the diffraction efficiency and the segment structure of phase grating. According to this analytic model, we then propose a design method to increase the diffraction signal at high odd orders and, meanwhile, to decrease it at the zeroth and even orders. The proposed method provides a fast and effective way to obtain the globally optimal grating structure in the valid scope. Furthermore, the design examples are also verified by means of numerical simulation tool–rigorous coupled-wave analysis (RCWA) software. As a result, the proposed method gives insight into the diffraction theory of segmented grating and the practical value to greatly improve the design efficiency.
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Sathukarn, Asmar, Chia Jia yi, Sakoolkan Boonruang, Mati Horprathum, Khwanchai Tantiwanichapan, Kiattiwut Prasertsuk, Chayut Thanapirom, Woraprach Kusolthossakul, and Kittipong Kasamsook. "The Simulation of a Surface Plasmon Resonance Metallic Grating for Maximizing THz Sensitivity in Refractive Index Sensor Application." International Journal of Optics 2020 (January 16, 2020): 1–8. http://dx.doi.org/10.1155/2020/3138725.
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Nowadays, the simplicity of both designing and fabrication process of a terahertz (THz) resonator-based sensing technique leads to its ongoing development. The consumable THz resonator needs to be easily integrated into an existing terahertz time domain spectroscopy (THz TDS) measurement system. It should also be able to be fabricated in a mass scale with a low production cost. In this work, a metal-coated surface plasmon resonance- (SPR-) based sensor is simulated and designed as a low-cost refractive index sensor utilizing rigorous coupled wave analysis (RCWA). To demonstrate our methodology, we design a gold-coated grating with a polydimethylsiloxane (PDMS) as a substrate, in order to perform quantitative analysis of gasoline-toluene mixture composition, which has a refraction index variation of 0.1 at THz frequency. The grating period is tuned such that its surface plasmon resonance (SPR) frequency matches with the peak frequency of the THz TDS system. Moreover, other grating parameters, i.e., a filling factor and a grating depth, are optimized to increase the sensor sensitivity and sharpen the resonance dip. High sensitivity up to 500 GHz/RIU with a refractive index resolution up to 0.01 is numerically revealed. The H-field of the designed grating is then evaluated to indicate a strong SPR excitation. The well-developed designed grating introduces a promising, low-cost, and easily fabricated THz refractive index sensor.
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Lee, ChaBum. "Design and Fabrication of Diffractive Light-Collecting Microoptical Device with 1D and 2D Lamellar Grating Structures." International Journal of Manufacturing Engineering 2014 (June 5, 2014): 1–7. http://dx.doi.org/10.1155/2014/101823.
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This paper presents the optimal design method of diffractive light-collecting microoptical device and its fabrication method by E-beam lithography, fast atom beam etching, and hot-embossing processes. The light-collecting device proposed in the paper is comprised of 9 (3 × 3) blocks of optical elements: 4 blocks of 1D lamellar grating structures, 4 blocks of 2D lamellar grating structures, and a single block of nonpatterned element at the center, which acts for lens to be able to collect the diffracted and transmitted lights from the lamellar grating structures into the focus area. The overall size of the light-collecting device is 300 × 300 μm2, and the size of each block was practically designed as 100 × 100 μm2. The performance of 1D and 2D lamellar grating structures was characterized in terms of diffraction efficiency and diffraction angle using a rigorous coupled-wave analysis (RCWA) method, and those geometric parameters, depth, pitch, and orientation, were optimized to achieve a high light-collecting efficiency. The master molds for the optimized structures were fabricated on Si substrate by E-beam lithography and fast atom beam etching processes. The 100 μm thick patterned polymethyl methacrylate (PMMA) film was then replicated by a hot-embossing process. As a result, the patterned PMMA film collected 63.0% more incident light than a nonpatterned one.
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Sakr, Enas, Deanna Dimonte, and Peter Bermel. "Metasurfaces with Fano resonances for directionally selective thermal emission." MRS Advances 1, no. 49 (2016): 3307–16. http://dx.doi.org/10.1557/adv.2016.526.
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ABSTRACTThermal emission impacts a wide variety of applications, including thermophotovoltaics, photovoltaics, photon-enhanced thermionic emission, selective solar absorption, incandescent lighting, and spectroscopy. Ordinary structures generally emit a broad range of wavelengths, angles, and polarizations. However, highly selective thermal emission has potential to greatly improve performance in many of these applications. While prior work has explored a wide range of structures to provide some degree of control of one or more of these attributes, there is an ongoing challenge in combining readily-fabricated, simple structures made of appropriate (e.g., heat-resistant) materials with the desired functionality. Here, we will focus on using metasurfaces in conjunction with refractory materials as a platform for achieving selective control of emission. These structures are built from sub-wavelength elements that support localization of surface plasmon polaritons or electromagnetic resonant modes with appropriate attributes. Modeling is performed using rigorous coupled wave analysis (RCWA), plus Kirchhoff’s law of thermal radiation, which is further validated using finite-difference time domain (FDTD) simulations and coupled-mode analysis. Such structures can be considered arbitrarily directional sources that can be carefully patterned in lateral directions to yield a thermal lens with a designed focal length and/or concentration ratio; the benefit of this approach is that it can enhance the view factor between thermal emitters and receivers, without restricting the area ratio or separation distance. This design and modeling platform is then applied to exclude thermal radiation over a certain range of angles. In this work, we study the effect of controlling the angular width and direction on the view factor, and we explore angular dependence of these angular selective structures.
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Hirose, Euichi, Daisuke Sakai, Tomohiro Shibata, Junji Nishii, Hiroyuki Mayama, Akihiro Miyauchi, and Jun Nishikawa. "Does the tunic nipple array serve to camouflage diurnal salps?" Journal of the Marine Biological Association of the United Kingdom 95, no. 5 (March 17, 2015): 1025–31. http://dx.doi.org/10.1017/s0025315415000119.
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The salp Thalia rhomboides is distributed in the shallow depths during the day, and is thus at increased risk of predation by visual predators and from the damaging effects of ultraviolet (UV) radiation compared with species distributed in deeper layers in the daytime. The integument (tunic) of T. rhomboides may have adaptive optical properties, but the absorption spectra of the unfixed tunic demonstrate that the tunic transmits UV as well as visible light, indicating that the tunic is not an effective barrier against UV radiation. Ultrastructural observation revealed that the surface of the tunic cuticle is covered in a nipple array consisting of hemispherical protuberances approximately 40 and 30 nm in diameter in solitary and aggregate zooids, respectively. Simulation of light reflection of a nipple array using rigorous coupled wave analysis (RCWA) indicated that the reflection is slightly lower for the nipple array than for a flat surface at high angles of incidence (θ > 80°). This result supports the idea that the nipple array serves to make the salp less visible. The simulation also indicated that the height and distribution of the salp nipple array do not have an optimal structure for causing an antireflection effect. A mechanical restriction might exist on the structures, and the nipple array could also serve another function. The size and distribution of nipples may be controlled by the need to meet the complex requirements of multiple essential functions.
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Yallapragada, Venkata Jayasurya, Ajith P. Ravishankar, Gajendra L. Mulay, Girish S. Agarwal, and Venu Gopal Achanta. "Observation of giant Goos-Hänchen and angular shifts at designed metasurfaces." Scientific Reports 6, no. 1 (January 13, 2016). http://dx.doi.org/10.1038/srep19319.
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Abstract Metasurfaces with sub-wavelength features are useful in modulating the phase, amplitude or polarization of electromagnetic fields. While several applications are reported for light manipulation and control, the sharp phase changes would be useful in enhancing the beam shifts at reflection from a metasurface. In designed periodic patterns on metal film, at surface plasmon resonance, we demonstrate Goos-Hanchen shift of the order of 70 times the incident wavelength and the angular shifts of several hundred microradians. We have designed the patterns using rigorous coupled wave analysis (RCWA) together with S-matrices and have used a complete vector theory to calculate the shifts as well as demonstrate a versatile experimental setup to directly measure the shifts. The giant shifts demonstrated could prove to be useful in enhancing the sensitivity of experiments ranging from atomic force microscopy to gravitational wave detection.
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Liu, Bo-Tau, and Sheng-Jie Tang. "Antireflective Optical Properties of Colloidal Subwavelength Nanostructured Surfaces." MRS Proceedings 1256 (2010). http://dx.doi.org/10.1557/proc-1256-n11-22.
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AbstractColloidal subwavelength nanostructured surfaces were fabricated by the deposition of uniform silica nanoparticles on a glass substrate by means of electrostatic attraction between charged colloidal particles and charged polyelectrolyte multilayers. The effects of surface morphology via the variation of nanoparticles on the antireflective properties of the nanostructured surfaces were investigated by the analysis of the reflection spectra and the SEM images. The Maxwell's equations were solved by a rigorous coupled-wave analysis (RCWA) to evaluate the experimental results. It was found that the reflective properties revealed by the simulation analysis were similar to the experimental results. The nanostructured surfaces with particles of ~120 nm in diameter yielded the most suitable performance for antireflection with respect to the visible-light region. In addition, the nanostructured surfaces showed the good anti-scratch when the nanoparticles were bound by polyethoxysiloxane.
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Liao, Wenyuan, Chuanchuan Li, Jian Li, Xiaofeng Guo, Wentao Guo, Xin Wei, and Manqing Tan. "Polarization control and mode optimization of 850 nm multi-mode VCSELs using surface grating." Applied Physics B 127, no. 2 (January 20, 2021). http://dx.doi.org/10.1007/s00340-020-07570-w.
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AbstractTo control the polarization of 850 nm multi-mode oxide-confined vertical-cavity surface-emitting lasers (VCSELs), monolithically integrated surface gratings are investigated. VCSELs with different grating parameters are simulated by the rigorous coupled-wave analysis (RCWA) method. Optical field intensity of two polarization orientations with different grating periods and duty cycles is obtained. The mode characteristics of VCSELs with different grating parameters are achieved by FDTD method. 850 nm surface grating VCSELs are fabricated and characterized, a maximum orthogonal polarization suppression ratio (OPSR) of 20.7 dB is observed. Meanwhile, VCSEL’s output mode characteristics are improved by integrating the surface grating. Application of integrated surface grating technique to achieve dynamically polarization-stable multi-mode VCSELs which enable polarization division multiplexed data transmission, the data throughput over a given link can be doubled.
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Wang, Puqun, Sara Azimi, Mark B. H. Breese, and Marius Peters. "Theoretical investigation of “nano-muffin” and inverted nano-pyramid surface textures for energy harvesting in very thin c-Si solar cells." MRS Proceedings 1638 (2014). http://dx.doi.org/10.1557/opl.2014.244.
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ABSTRACTNano-scale surface textures have been developed as photon management schemes for crystalline silicon (c-Si) solar cells with very thin absorber layers to compensate for light absorption losses. This paper investigates the optical properties of periodic “nano-muffin” and inverted nano-pyramid surface textures, simulated using the Rigorous Coupled Wave Analysis (RCWA) method. Obtained results are compared against those of a planar silicon film with equal thickness. The simulation results demonstrate that “nano-muffin” and inverted nano-pyramid surface textures with a small aspect ratio are able to achieve substantial absorption enhancement over a broadband wavelength range. Further investigation indicates that “nano-muffin” surface textures could trap light by concentrating light within a volume close to the texture (micro-lensing effect). With such nano-scale textures, light trapping similar to that of much larger scale textures can be achieved.
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Zhang, Yutao, and Yimin Xuan. "Spectral Features of an Omnidirectional Narrowband Emitter." Journal of Heat Transfer 134, no. 10 (August 7, 2012). http://dx.doi.org/10.1115/1.4006156.
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A microscale-structured surface consisting of heavily doped silicon rectangle grating and slotted silver layer is studied for omnidirectional narrowband emitter. Numerical simulation is implemented to obtain spectral emittance in mid-infrared region (6–16 μm) for the transverse magnetic incidence by using the rigorous coupled-wave analysis (RCWA) method. The effects of structural parameters and incident angle on its spectral emittance are investigated. In virtue of the microcavity effect, an omnidirectional narrowband emitter is proposed. By selecting a group of structural parameters, its peak emittance reaches as high as 0.998, and the peak width Δλ/λ of the emittance peak is as narrow as 0.03 at the specified wavelength. The results reveal that our proposed structured surface has the nice spectral features of angular uniformity and wavelength-selective characteristic, which can be applied to design novel narrowband thermal emitters and detectors in the infrared region.
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Yang, Peiyan, Hong Ye, and Zhuomin M. Zhang. "Experimental Demonstration of the Effect of Magnetic Polaritons on the Radiative Properties of Deep Aluminum Gratings." Journal of Heat Transfer 141, no. 5 (March 27, 2019). http://dx.doi.org/10.1115/1.4042698.
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Despite the abundant theoretical studies of magnetic polaritons (MPs) in tailoring the radiative properties of nanostructures, experimental investigation of MPs in deep metal gratings is still lacking. This work experimentally demonstrates the excitation of MP from several microfabricated aluminum gratings in the mid-infrared region by measuring the specular reflectance (zeroth-order diffraction) of the specimen using a Fourier-transform infrared (FTIR) spectrometer. The rigorous coupled-wave analysis (RCWA) and an LC-circuit model are employed to elucidate the mechanism of various resonant modes and their coupling effect. The influence of incidence angle, plane of incidence, polarization, and the trench depth on the spectral reflectance is also discussed. Moreover, the MP dispersion for off-plane layout has been investigated and demonstrated for the first time. The insight gained from this work may facilitate future design and applications of subwavelength periodic structures with desired radiative properties.
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Wang, Weijie, Ceji Fu, and Wenchang Tan. "Thermal Radiative Properties of a SiC Grating on a Photonic Crystal." Journal of Heat Transfer 135, no. 9 (July 26, 2013). http://dx.doi.org/10.1115/1.4024468.
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Spectral and directional control of thermal emission holds substantial importance in different kinds of applications, where heat transfer is predominantly by thermal radiation. Several configurations have previously been proposed, like using gratings, photonic crystals (PCs) and resonant cavities. In the present work, we investigate the thermal radiative properties of a microstructure consisting of a SiC grating on a photonic crystal. The emissivity of the microstructure is calculated with the rigorous coupled-wave analysis (RCWA) algorithm as a function of the angular frequency and the emission angle. The results reveal that thermal emission from the microstructure can exhibit very novel feature compared to those previously studied. Especially, significantly enhanced thermal emission can be achieved in a broad spectral band due to excitation of surface photon polaritons (SPhPs), PC modes, magnetic polaritons (MPs) and the coupling between them. We show that it is possible to flexibly control the thermal emission feature by adjusting the microstructure's dimensional parameters properly.
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Junfei Fang, Yuchun Gou, and Jianping Deng. "Complex trapezoid grating for light trapping in thin-film solar cells: super-fine structure." Optica Applicata 50, no. 3 (2020). http://dx.doi.org/10.37190/oa200305.
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The research of the optimal surface structure has attracted considerable interest because of its potential application in light trapping in thin-film solar cells (TFSCs). In this paper, a super-fine structure named complex trapezoid grating is proposed to improve the optical absorption comparing to the conventional simple trapezoid grating in a-Si:H TFSCs. The numerical calculation by utilizing rigorous coupled-wave analysis (RCWA) is conducted to obtain the optical absorption of the structured surface. The results demonstrate that, compared to a planar slab, the optimized-simple trapezoid grating shows 97% enhancement of power conversion efficiency η while the complex trapezoid grating shows 131% enhancement. Obviously, the complex trapezoid grating exhibits a better performance than the simple grating, which is due to the perfect antireflective effect and microcavity resonance effect. The angular response of the optical absorption in a-Si:H TFSCs was also investigated. The results further indicate that it is a better way to select the complex trapezoid grating in improving the optical absorption of silicon-based TFSCs.
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Watjen, J. I., X. L. Liu, B. Zhao, and Z. M. Zhang. "A Computational Simulation of Using Tungsten Gratings in Near-Field Thermophotovoltaic Devices." Journal of Heat Transfer 139, no. 5 (February 14, 2017). http://dx.doi.org/10.1115/1.4035356.
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Near-field thermophotovoltaic (NFTPV) devices have received much attention lately as an alternative energy harvesting system, whereby a heated emitter exchanges super-Planckian thermal radiation with a photovoltaic (PV) cell to generate electricity. This work describes the use of a grating structure to enhance the power throughput of NFTPV devices, while increasing the energy conversion efficiency by ensuring that a large portion of the radiation entering the PV cell is above the band gap. The device contains a high-temperature tungsten grating that radiates photons to a room-temperature In0.18Ga0.82Sb PV cell through a vacuum gap of several tens of nanometers. Scattering theory is used along with the rigorous coupled-wave analysis (RCWA) to calculate the radiation energy exchange between the grating emitter and the TPV cell. A parametric study is performed by varying the grating depth, period, and ridge width in the range that can be fabricated using available fabrication technologies. It is found that the power output can be increased by 40% while improving the efficiency from 29.9% to 32.0% with a selected grating emitter as compared to the case of a flat tungsten emitter. Reasons for the enhancement are found to be due to the enhanced energy transmission coefficient close to the band gap. This work shows a possible way of improving NFTPV and sheds light on how grating structures interact with thermal radiation at the nanoscale.
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Jiao, Y., L. H. Liu, and P. F. Hsu. "Widening Absorption Band of Grating Structure With Complex Dual-Groove Grating." Journal of Heat Transfer 135, no. 3 (February 8, 2013). http://dx.doi.org/10.1115/1.4007881.
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The wavelength-selective radiative property is becoming a noticeable requirement in various technological fields. There are many researches that have been focused on the radiative properties of metal periodic microstructure surface. However, the spectral bandwidth of high absorptance is often too narrow if excited by the conventional grating structures. In order to solve this problem, two novel periodic grating structures are proposed in this paper, which can increase the effective bandwidth of high absorption peaks. One of the new periodic grating structures, called dual-groove grating, is constructed by adding a rectangular groove at the bottom of the simple grating's groove through a secondary microscale processing. The other grating structure, which is called complex dual-groove grating, is constructed by superposing a dual-groove grating with a simple grating within one period. Aluminum grating structure is taken as an example to show the advantage of proposed structures on increasing effective bandwidth of high absorption peaks within mid-infrared and far-infrared spectra. The rigorous coupled-wave analysis (RCWA) is used to calculate the absorptance of periodic grating structures. The results shows that, two close absorption peaks and three connecting absorption peaks are obtained respectively for the two periodic grating structures. The effective bandwidth of high absorption peaks within interested wavelength band is improved obviously by these two microscale grating structures.