Journal articles on the topic 'Grating'
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1
Wang, Ye, Xiuhua Fu, Yongyi Chen, Hangyu Peng, Li Qin, Yongqiang Ning, and Lijun Wang. "Optimal Design and Analysis of 4.7 μm Hybrid Deep Dielectric High Efficiency Transmission Gratings." Micromachines 13, no. 10 (October 10, 2022): 1706. http://dx.doi.org/10.3390/mi13101706.
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There is currently no transmission grating with good diffraction efficiency in the 4.7 μm band. Metal gratings at this wavelength are all reflective gratings which has a diffraction efficiency of lower than 90% and lower laser damage threshold. In this paper, we bring up a design of a multi-layer transmission grating with both high diffraction efficiency and wide working wavelength band. We have proved that the transmission grating made of composite materials has an average diffraction effectiveness of more than 96% throughout the whole spectral range of 200 nm. Meanwhile, the theoretically computed transmission grating has a highest first-order diffraction efficiency of more than 99.77% at 4746 nm. This multilayer dielectric film transmission grating’s optimized design may further boost spectral beam combining power, providing a practical technique for increasing SBC power and brightness.
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Ichihara, Shigeru, and Kenji Susami. "Temporal-Discontinuity Detection with Contrast-Modulated Gratings." Perception 24, no. 11 (November 1995): 1257–64. http://dx.doi.org/10.1068/p241257.
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Three experiments on temporal-discontinuity detection were carried out. In experiment 1, temporal-discontinuity thresholds were measured for sinusoidal gratings by the use of the double-staircase method. A sinusoidal grating was presented twice successively. The subject judged whether or not an interval was present. The temporal-discontinuity threshold increased as the spatial frequency of the grating increased, but decreased as the contrast of the grating increased. In experiment 2, contrast-modulated gratings were used instead of the sinusoidal grating. The temporal-discontinuity threshold increased as the carrier frequency increased, and the threshold for each contrast-modulated grating was similar to that for the no-modulation (sinusoidal) grating whose contrast was the same as the maximum local contrast of the contrast-modulated grating. In experiment 3, temporal-discontinuity thresholds were measured for low-contrast (3%) sinusoidal gratings. The thresholds were very low, even for such low-contrast gratings. These results suggest that the low-spatial-frequency channels are not involved in detecting the modulation frequency of the contrast-modulated grating. Rather, the local contrast seems to be the determinant of the detection of the contrast-modulated grating itself.
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Kajkowska, Marta, Miłosz Sławomir Chychłowski, Sławomir Ertman, and Piotr Lesiak. "Dual-Period Polarization-Dependent Diffraction Gratings Based on a Polymer-Stabilized Liquid Crystal." Materials 16, no. 23 (November 24, 2023): 7313. http://dx.doi.org/10.3390/ma16237313.
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In this paper, we demonstrate the first ever dual-period diffraction gratings that do not require electrical tuning to obtain the effect of period change. Our method allows for multiplication of the base period by proper modification of the subsequent slits of the grating. The proposed elements are fabricated by selective photopolymerization of a composite based on a nematic liquid crystal. The gratings are formed by polymer stabilization of a liquid crystal in different orientations of the molecules in selected grating slits to allow for period manipulation. The operating principle is based on changing the phase delay introduced by the slits depending on polarization direction of incident light with respect to the director in each type of slit, which allows to change the grating’s period. The proposed technique was successfully utilized to obtain diffraction gratings with either doubling or tripling of the period.
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Ivanov, Oleg V., Paulo Caldas, and Gaspar Rego. "Simulation of the Transmission Spectrum of Long-Period Fiber Gratings Structures with a Propagating Acoustic Shock Front." Sensors 21, no. 21 (October 29, 2021): 7212. http://dx.doi.org/10.3390/s21217212.
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In this paper, we investigate modification of transmission spectra of long-period fiber grating structures with an acoustic shock front propagating along the fiber. We simulate transmission through inhomogeneous long-period fiber gratings, π-shift and reflective π-shift gratings deformed by an acoustic shock front. Coupled mode equations describing interaction of co-propagating modes in a long-period fiber grating structures with inhomogeneous deformation are used for the simulation. Two types of apodization are considered for the grating modulation amplitude, such as uniform and raised-cosine. We demonstrate how the transmission spectrum is produced by interference between the core and cladding modes coupled at several parts of the gratings having different periods. For the π-shift long-period fiber grating having split spectral notch, the gap between the two dips becomes several times wider in the grating with the acoustic wave front than the gap in the unstrained grating. The behavior of reflective long-period fiber gratings depends on the magnitude of the phase shift near the reflective surface: an additional dip is formed in the 0-shift grating and the short-wavelength dip disappears in the π-shift grating.
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Inneam, Chanikan, Keerayoot Srinuanjan, and Witoon Yindeesuk. "An application of reflective holographic gratings for measurement of cylindrical curvature." Journal of Physics: Conference Series 2145, no. 1 (December 1, 2021): 012054. http://dx.doi.org/10.1088/1742-6596/2145/1/012054.
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Abstract This paper presented an application of reflective holographic gratings for the measurement of cylindrical curvature. The surface of the fabricated holographic grating was coated with gold by the sputtering method, where it became a reflective holographic grating. The grating was attached to the surface of various radius cylindrical objects. The diffraction pattern produced by the bent grating with different radius was observed by illuminating a laser beam normal to the grating surface. The gratings constant were calculated from the observed diffraction pattern. The relationship between the grating constants and the radius of cylindrical objects was obtained. The grating constant and the reciprocal of the radius of cylindrical objects was a linear relationship, with the least R-square between 0.85-0.97. Moreover, the y-intercept of the relationship between the grating constants and the reciprocal radius was consistent with the grating constant of the non-bended grating. As the radius of the grating approach is infinite, the reciprocal of the radius approaches zero, which is a non-bend grating. We can apply this method to measure the radius of cylindrical objects.
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Yang, Zhiyong, Xiaochen Ma, Daguo Yu, Bin Cao, Qianqi Niu, Mengwei Li, and Chenguang Xin. "An Ultracompact Angular Displacement Sensor Based on the Talbot Effect of Optical Microgratings." Sensors 23, no. 3 (January 17, 2023): 1091. http://dx.doi.org/10.3390/s23031091.
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Here, we report an ultracompact angular displacement sensor based on the Talbot effect of optical microgratings. Periodic Talbot interference patterns were obtained behind an upper optical grating. By putting another grating within the Talbot region, the total transmission of the two-grating structure was found to be approximatively in a linear relationship with the relative pitch angle between the two gratings, which was explained by a transversal shift of the Talbot interference patterns. The influence of the grating parameters (e.g., the grating period, the number of grating lines and the gap between the two gratings) was also studied in both a simulation and an experiment, showing a tunable sensitivity and range by simply changing the grating parameters. A sensitivity of 0.19 mV/arcsec was experimentally obtained, leading to a relative sensitivity of 0.27%/arcsec within a linear range of ± 396 arcsec with the 2 μm-period optical gratings. Benefitting from tunable properties and an ultracompact structure, we believe that the proposed sensor shows great potential in applications such as aviation, navigation, robotics and manufacturing engineering.
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Tian, Zhenhua, Lingyu Yu, Xiaoyi Sun, and Bin Lin. "Damage localization with fiber Bragg grating Lamb wave sensing through adaptive phased array imaging." Structural Health Monitoring 18, no. 1 (February 19, 2018): 334–44. http://dx.doi.org/10.1177/1475921718755572.
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Fiber Bragg gratings are known being immune to electromagnetic interference and emerging as Lamb wave sensors for structural health monitoring of plate-like structures. However, their application for damage localization in large areas has been limited by their direction-dependent sensor factor. This article addresses such a challenge and presents a robust damage localization method for fiber Bragg grating Lamb wave sensing through the implementation of adaptive phased array algorithms. A compact linear fiber Bragg grating phased array is configured by uniformly distributing the fiber Bragg grating sensors along a straight line and axially in parallel to each other. The Lamb wave imaging is then performed by phased array algorithms without weighting factors (conventional delay-and-sum) and with adaptive weighting factors (minimum variance). The properties of both imaging algorithms, as well as the effects of fiber Bragg grating’s direction-dependent sensor factor, are characterized, analyzed, and compared in details. The results show that this compact fiber Bragg grating array can precisely locate damage in plates, while the comparisons show that the minimum variance method has a better imaging resolution than that of the delay-and-sum method and is barely affected by fiber Bragg grating’s direction-dependent sensor factor. Laboratory tests are also performed with a four–fiber Bragg grating array to detect simulated defects at different directions. Both delay-and-sum and minimum variance methods can successfully locate defects at different positions, and their results are consistent with analytical predictions.
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Xie, Hui Min, Yan Jie Li, Hua Du, Bing Pan, Qiang Luo, Chang Zhi Gu, and Hai Chang Jiang. "The Technique for Fabricating Submicron Moiré Grating Using FIB Milling." Advanced Materials Research 47-50 (June 2008): 710–13. http://dx.doi.org/10.4028/www.scientific.net/amr.47-50.710.
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In this study, focused gallium ion (Ga+) beam is utilised to fabricate micro/submicron spacing gratings on specimen surface. The grating types include: parallel, cross, and hybrid (grating with double-frequency). Several hybrid gratings with double frequency were produced in combination mode or superposition mode, which have a good potential to measure deformation within different range. Techniques for producing different type of gratings are discussed in detail. As an application, a 5000 lines/mm grating was fabricated on an amorphous SIC MEMS cantilever and was successfully used to measure its virtual strain with aid of digital moiré. The experimental results verify the feasibility of fabricating high frequency grating on metal or non-metal surface using the FIB milling and the resultant grating can be used to measure micro-deformation.
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Yang, Ying Li, and Guo Dong Wang. "Coupling Efficiency Analysis of Different Top Coupling Grating for Quantum Well Infrared Photo-Detector." Applied Mechanics and Materials 273 (January 2013): 515–18. http://dx.doi.org/10.4028/www.scientific.net/amm.273.515.
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The relative coupling efficiency of different top coupling grating for quantum well infrared photo-detector is calculated by finite difference time domain algorithms. The relative coupling efficiency respect to the grating parameters, such as, grating period and grating depth is analyzed for both square lattice and hexagonal lattice structure gratings. By comparison, it can be concluded that the optimization grating parameters is differential for different grating structure.
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ZHANG, GUOQUAN, FANG BO, FENG GAO, RONG DONG, YANFEI TU, and JINGJUN XU. "SLOW AND FAST LIGHTS WITH MOVING AND STATIONARY REFRACTIVE INDEX GRATINGS IN SOLIDS AT ROOM TEMPERATURE." International Journal of Modern Physics B 22, no. 05 (February 20, 2008): 447–68. http://dx.doi.org/10.1142/s0217979208038788.
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We reviewed the recent progress on slow and fast lights in solids at room temperature based on moving and stationary refractive index gratings. A dispersive photorefractive phase coupling associated with moving gratings results in slow and fast lights. In principle, such phase-coupling-induced slow and fast lights can be observed in any nonlinear wave mixing process with a dispersive phase coupling effect. The slow and fast lights in the stationary gratings are also discussed. One advantage of the stationary gratings is the possibility to engineer the dispersion slope of the grating through designing the grating structure and parameters. As an example, we show that the dispersion slope of the gratings is enhanced significantly by stratifying a series of identical volume index gratings with homogeneous optical buffer layers sandwiched between every two neighboring grating layers. The slow and fast lights, therefore, can be controlled more effectively in such specifically designed grating structures than in the homogeneous gratings. Another advantage is the high transparency of the slow and fast lights with appropriate grating structure and parameters. Issues such as the pulse broadening effect and the pulse distortion are addressed. The slow and fast light techniques have many important potential applications such as optical delay lines and optical buffers.
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Zhai, Tianrui, Liang Han, Xiaojie Ma, and Xiaolei Wang. "Low-Threshold Microlasers Based on Holographic Dual-Gratings." Nanomaterials 11, no. 6 (June 9, 2021): 1530. http://dx.doi.org/10.3390/nano11061530.
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Among the efforts to improve the performances of microlasers, optimization of the gain properties and cavity parameters of these lasers has attracted significant attention recently. Distributed feedback lasers, as one of the most promising candidate technologies for electrically pumped microlasers, can be combined with dual-gratings. This combination provides additional freedom for the design of the laser cavity. Here, a holographic dual-grating is designed to improve the distributed feedback laser performance. The holographic dual-grating laser consists of a colloidal quantum dot film with two parallel gratings, comprising first-order (210 nm) and second-order (420 nm) gratings that can be fabricated easily using a combination of spin coating and interference lithography. The feedback and the output from the cavity are controlled using the first-order grating and the second-order grating, respectively. Through careful design and analysis of the dual-grating, a balance is achieved between the feedback and the cavity output such that the lasing threshold based on the dual-grating is nearly half the threshold of conventional distributed feedback lasers. Additionally, the holographic dual-grating laser shows a high level of stability because of the high stability of the colloidal quantum dots against photobleaching.
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Ye, Weinan, Rong Cheng, Ming Zhang, Yu Zhu, Leijie Wang, Jinchun Hu, and Xin Li. "Grating Interferometer with Redundant Design for Performing Wide-Range Displacement Measurements." Sensors 22, no. 10 (May 14, 2022): 3738. http://dx.doi.org/10.3390/s22103738.
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Grating interferometers that use large two-dimensional grating splice modules for performing wide-range measurements have significant advantages for identifying the position of the wafer stage. However, the manufacturing process of large two-dimensional grating splice modules is very difficult. In contrast to existing redundant designs in the grating line dimension, we propose a novel interferometric reading head with a redundant design for obtaining wide-range displacement measurements. This interferometric reading head uses a one-dimensional grating splice module, and it was observed to be compatible with two orthogonal gratings. We designed a grating interferometer system composed of four reading heads to achieve a wide range of measurements and verified it using ZEMAX simulation. By conducting experiments, we were able to verify the compatibility of the reading head with gratings possessing different grating line directions; the measurement noise was found to be less than 0.3 nm.
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Bartelt, Hartmut. "Fiber Bragg Grating Sensors and Sensor Arrays." Advances in Science and Technology 55 (September 2008): 138–44. http://dx.doi.org/10.4028/www.scientific.net/ast.55.138.
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Fiber Bragg gratings have found widespread application in sensor systems, e. g. for temperature, strain or refractive index measurements. The concept of fiber Bragg gratings allows also in a simple way the realisation of arrays of such sensors. The development of such optical fiber sensor systems often requires special fibers and grating structures which may go beyond more conventional Bragg grating structures in typical communication fibers. Concerning fibers there is, for example., a need of achieving fiber gratings in small diameter fibers and fiber tapers as well as in microstructured fibers. Special fiber grating structures are of interest e.g. in the visible wavelength range, which requires smaller spatial structures compared to more conventional gratings in the near infrared wavelength region. Examples for such modern developments in fiber Bragg grating technology for sensor applications will be presented and discussed.
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Bartelt, Hartmut. "Trends in Bragg Grating Technology for Optical Fiber Sensor Applications." Key Engineering Materials 437 (May 2010): 304–8. http://dx.doi.org/10.4028/www.scientific.net/kem.437.304.
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Fiber Bragg gratings have found widespread and successful applications in optical sensor systems, e. g. for temperature, strain or refractive index measurements. Such sensor elements are fiber integrated, are applicable under harsh environmental conditions, and can be easily multiplexed. In order to further extend the field of applications, there is a great interest in specifically adapted Bragg gratings, in Bragg grating structures with increased stability, or in the use of special fiber types for grating inscription. The paper discusses such specific concepts for grating inscription, covers novel aspects of fiber gratings in small diameter fibers or in fiber tapers, of gratings in pure silica fibers without UV sensitivity, of grating inscription in different microstructured fibers or photonic crystal fibers, and investigates the concept of femtosecond inscription and the extension of the Bragg reflection wavelengths down to the visible range.
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Shou, Tiande, Xiangrui Li, Yifeng Zhou, and Bing Hu. "Adaptation of visually evoked responses of relay cells in the dorsal lateral geniculate nucleus of the cat following prolonged exposure to drifting gratings." Visual Neuroscience 13, no. 4 (July 1996): 605–13. http://dx.doi.org/10.1017/s0952523800008518.
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AbstractAdaptation of visual cortical cells' responses is observed following repeated presentation of grating stimuli. Grating adaptation is believed to exist only at the cortical level. The purpose of this study was to see if grating adaptation also occurs in the lateral geniculate nucleus. We studied the responses of 164 relay cells in layer A and A1 of the dorsal lateral geniculate nucleus (LGNd) to grating stimuli. Normal cats, as well as cats in which visual cortex was ablated, were studied. Adaptation was investigated using repeated presentation of gratings of different contrasts and orientations. The results showed the following: (1) Grating adaptation reduced the responses of 46% of the LGNd cells recorded. The responses normally decreased within 30 s and then stabilized. However, there was heterogeneity in the effects observed. About 38% of the cells studied were not affected by the adapting gratings. Some cells (16%) showed facilitation rather than habituation of their responses to test stimuli. (2) There was no significant difference between X and Y cells in their susceptibility to adaptation. This suggests that grating adaptation is a general property, independent of cell type. (3) The contrast-response curves of 57% of the LGNd cells studied shifted down after exposure to high-contrast adapting gratings. (4) Adapting gratings of the cells' preferred orientation decreased the orientation sensitivity of 56% of the orientation-sensitive cells. Adapting gratings at the nonpreferred orientation did not affect orientation sensitivity. (5) Prolonged grating adaptation also reduced the responses of 49% of the LGNd cells after inactivation of cortical inputs to the LGNd.
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Xie, Hui Min, Zhan Wei Liu, Ming Zhang, Peng Wan Chen, Feng Lei Huang, and Qing Ming Zhang. "Nano-Grating Fabrication Technique." Key Engineering Materials 326-328 (December 2006): 131–34. http://dx.doi.org/10.4028/www.scientific.net/kem.326-328.131.
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In this paper, a novel nano-moiré grating fabrication technique was proposed for nanometer deformation measurement. The grating fabrication process was performed with the aid of Atomic Force Microscope (AFM) on the basis of micro-fabrication technique. On the analysis of some correlative factors of influencing grating line quality, some important experimental parameters were optimized. In this study, some parallel and cross nano-gratings with frequencies of from 10000lines/mm to 20000lines/mm were fabricated. The successful experimental results demonstrate that the nano-grating fabrication technique is feasible and also indicated that these nano-gratings with nano-moiré method can be applied to deformation measurement, which offers a nanometer sensitivity and spatial resolution.
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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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Mateev, Georgi, Lian Nedelchev, Ludmila Nikolova, Branimir Ivanov, Velichka Strijkova, Elena Stoykova, Kihong Choi, Joongki Park, and Dimana Nazarova. "Two-Dimensional Polarization Holographic Gratings in Azopolymer Thin Films: Polarization Properties in the Presence or Absence of Surface Relief." Photonics 10, no. 7 (June 26, 2023): 728. http://dx.doi.org/10.3390/photonics10070728.
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During polarization holographic recording in azopolymer thin films, usually together with the volume anisotropic grating, a surface relief grating (SRG) is also formed. By using two consecutive exposures, it is possible to obtain a two-dimensional (2D) grating. To the best of our knowledge, the polarization properties of such gratings have not been studied yet. To determine the influence of the surface relief on the polarization selectivity of the 2D gratings, we propose two methods to suppress the SRG formation: by varying the recording conditions or varying the sample structure. In these experiments we have used the commercially available azopolymer PAZO, poly[1-4-(3-carboxy-4-hydrophenylazo) benzene sulfonamido]-1,2-ethanediyl, sodium salt] to perform the polarization holographic recording using a 442 nm He-Cd laser. As indicated by our results, when the surface relief is present, it strongly dominates the response of the 2D grating and it behaves almost as a scalar polarization insensitive grating. Conversely, when the SRG formation is suppressed, the polarization properties of the 2D grating in all four diffracted orders are very well pronounced. In this way, we demonstrate that we can easily control SRG formation and, if desired, obtain 2D grating with high surface relief modulation, or alternatively record polarization-selective 2D gratings with virtually no surface relief.
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Lei, Lihua, Lijie Liang, Liqin Liu, Yaoqiong Shen, Yuqing Guan, Yujie Zhang, Wenzhe Zou, Chuangwei Guo, and Yunxia Fu. "A Study on Length Traceability and Diffraction Efficiency of Chromium Gratings." Photonics 11, no. 3 (March 4, 2024): 233. http://dx.doi.org/10.3390/photonics11030233.
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Measurement traceability is a prerequisite for achieving accurate and reliable results as well as technical standardization. The period of Chromium (Cr) gratings fabricated by atomic lithography can be directly traced back to natural constants. Applying the Cr grating to grating interferometry can achieve nanometer measurement traceability. This research aims to analyze the diffraction efficiency characteristics of self-traceable Cr gratings to provide a theoretical basis for the fabrication and application of Cr gratings. In this regard, we establish the theoretical model of the laser beam incident angle and grating diffraction efficiency using the rigorous coupled-wave method. Then, we analyze the influence of the laser beam incident angle on grating diffraction efficiency by simulation, verify the accuracy of the theoretical model, and finally build a measurement system for grating diffraction efficiency. Through experiments, we find that the diffraction efficiency of the grating shows a rapid increase to reach a stable maximum value followed by a decrease, when a laser beam with a wavelength of 405 nm is incident on the surface of a self-traceable grating in Transverse Magnetic (TM) polarization and the incident angle changes within an effective range. The experimental results are consistent with the trend of theoretical calculation results.
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Wen, Han, Andrew A. Gomella, Ajay Patel, Douglas E. Wolfe, Susanna K. Lynch, Xianghui Xiao, and Nicole Morgan. "Boosting phase contrast with a grating Bonse–Hart interferometer of 200 nanometre grating period." Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 372, no. 2010 (March 6, 2014): 20130028. http://dx.doi.org/10.1098/rsta.2013.0028.
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We report on a grating Bonse–Hart interferometer for phase-contrast imaging with hard X-rays. The method overcomes limitations in the level of sensitivity that can be achieved with the well-known Talbot grating interferometer, and without the stringent spectral filtering at any given incident angle imposed by the classic Bonse–Hart interferometer. The device operates in the far-field regime, where an incident beam is split by a diffraction grating into two widely separated beams, which are redirected by a second diffraction grating to merge at a third grating, where they coherently interfere. The wide separation of the interfering beams results in large phase contrast, and in some cases absolute phase images are obtained. Imaging experiments were performed using diffraction gratings of 200 nm period, at 22.5 keV and 1.5% spectral bandwidth on a bending-magnetic beamline. Novel design and fabrication process were used to achieve the small grating period. Using a slitted incident beam, we acquired absolute and differential phase images of lightly absorbing samples. An advantage of this method is that it uses only phase modulating gratings, which are easier to fabricate than absorption gratings of the same periods.
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Swanston, Michael T., and Nicholas J. Wade. "Motion over the Retina and the Motion Aftereffect." Perception 21, no. 5 (October 1992): 569–82. http://dx.doi.org/10.1068/p210569.
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The motion aftereffect (MAE) was measured with retinally moving vertical gratings positioned above and below (flanking) a retinally stationary central grating (experiments 1 and 2). Motion over the retina was produced by leftward motion of the flanking gratings relative to the stationary eyes, and by rightward eye or head movements tracking the moving (but retinally stationary) central grating relative to the stationary (but retinally moving) surround gratings. In experiment 1 the motion occurred within a fixed boundary on the screen, and oppositely directed MAEs were produced in the central and flanking gratings with static fixation; but with eye or head tracking MAEs were reported only in the central grating. In experiment 2 motion over the retina was equated for the static and tracking conditions by moving blocks of grating without any dynamic occlusion and disclosure at the boundaries. Both conditions yielded equivalent leftward MAEs of the central grating in the same direction as the prior flanking motion, ie an MAE was consistently produced in the region that had remained retinally stationary. No MAE was recorded in the flanking gratings, even though they moved over the retina during adaptation. When just two gratings were presented, MAEs were produced in both, but in opposite directions (experiments 3 and 4). It is concluded that the MAE is a consequence of adapting signals for the relative motion between elements of a display.
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VICTOR, JONATHAN D., KEITH P. PURPURA, and MARY M. CONTE. "Chromatic and luminance interactions in spatial contrast signals." Visual Neuroscience 15, no. 4 (April 1998): 607–24. http://dx.doi.org/10.1017/s0952523898154032.
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We report VEP studies which delineate interactions between chromatic and luminance contrast signals. We examined responses to sinusoidal luminance gratings undergoing 4-Hz square-wave contrast reversal, upon which standing gratings with various admixtures of luminance and chromatic contrast were alternately superimposed and withdrawn. The presence of the standing grating induced a VEP component at the fundamental frequency of the contrast-reversal grating. This VEP component appeared without any appreciable lag, and did not vary in amplitude over the 4 s during which the standing grating was present. The observed fundamental response differed from the fundamental component that would be expected from the known interaction between the luminance component of the standing grating with the modulated grating (Bodis-Wollner et al., 1972; Bobak et al., 1988), in three ways: (1) The fundamental response was not nulled for standing gratings that were isoluminant or near-isoluminant. (2) The chromatic dependence of the fundamental response implied an S-cone input to the interaction. (3) No single mechanism (driven by a linear combination of cone signals) could account quantitatively for the size of this response, particularly when the standing grating strongly modulated two cones in phase.
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Hidrovo, I., J. Dey, H. Meyer, D. S. Hussey, N. N. Klimov, L. G. Butler, K. Ham, and W. Newhauser. "Neutron interferometry using a single modulated phase grating." Review of Scientific Instruments 94, no. 4 (April 1, 2023): 045110. http://dx.doi.org/10.1063/5.0106706.
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Neutron grating interferometry provides information on phase and small-angle scatter in addition to attenuation. Previously, phase grating moiré interferometers (PGMI) with two or three phase gratings have been developed. These phase-grating systems use the moiré far-field technique to avoid the need for high-aspect absorption gratings used in Talbot–Lau interferometers (TLI) that reduce the neutron flux reaching the detector. We first demonstrate, through theory and simulations, a novel phase grating interferometer system for cold neutrons that requires a single modulated phase grating (MPG) for phase-contrast imaging, as opposed to the two or three phase gratings in previously employed PGMI systems. The theory shows the dual modulation of MPG with a large period and a smaller carrier pitch P, resulting in large fringes at the detector. The theory was compared to the full Sommerfeld–Rayleigh diffraction integral simulator. Then, we proceeded to compare the MPG system to experiments in the literature that use a two-phase-grating-based PGMI with best-case visibility of around 39%. The simulations of the MPG system show improved visibility in comparison to that of the two-phase-grating-based PGMI. An MPG with a modulation period of 300 µm, the pitch of 2 µm, and grating heights with a phase modulation of ([Formula: see text], illuminated by a monochromatic beam produces visibility of 94.2% with a comparable source-to-detector distance (SDD) as the two-phase-grating-based PGMI. Phase sensitivity, another important performance metric of the grating interferometer, was compared to values available in the literature, viz. the conventional TLI with the phase sensitivity of 4.5 × 103 for an SDD of 3.5 m and a beam wavelength of 0.44 nm. For a range of modulation periods, the MPG system provides comparable or greater theoretical maximum phase sensitivity of 4.1 × 103 to 10.0 × 103 for SDDs of up to 3.5 m. This proposed MPG system appears capable of providing high-performance PGMI that obviates the need for the alignment of two phase gratings.
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Takata, Yoshiaki. "Conditions inducing reliable transient gratings of a LaCoO3 thin film using transient grating technique." Journal of Materials Research 19, no. 11 (November 1, 2004): 3149–51. http://dx.doi.org/10.1557/jmr.2004.0422.
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First, a grating decay rate and a thermal diffusion rate of the transient gratings are determined out of the energy-time trace observed by using a transient grating technique with 266-nm laser pulse inducing transient gratings in a LaCoO3 thin film. Second, the grating models aimed at studying two different thermal diffusion phenomena in contrast with the previous paper are described. The difference between both phenomena is attributable to the volume of photon scattering to characterize induced transient gratings. It is concluded that a reliable energy-time trace is observed when the transient gratings with a thickness smaller than a film are induced on the very surface of a thin film sample.
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Movchan, N. V., R. C. McPhedran, A. B. Movchan, and C. G. Poulton. "Wave scattering by platonic grating stacks." Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences 465, no. 2111 (August 12, 2009): 3383–400. http://dx.doi.org/10.1098/rspa.2009.0301.
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We address the problem of scattering of flexural waves obeying the biharmonic equation by a stack of a finite number of gratings. We express the solution of the scattering problem for a single grating in terms of reflection and transmission matrices, incorporating the effects of both propagating and evanescent incident waves. The plane wave expansion coefficients above and below the grating are linked to multipole coefficients within the grating using the grating sums and the Rayleigh identities. We derive the recurrence procedure giving the reflection and transmission matrices of the stack in terms of those of individual layers. Trapped waves between a pair of gratings are investigated.
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Zhu, Xiaojun, Shuai Li, Ang Sun, Yongquan Pan, Wen Liu, Yue Wu, Guoan Zhang, and Yuechun Shi. "A mid-infrared focusing grating coupler with a single circular arc element based on germanium on silicon." Beilstein Journal of Nanotechnology 14 (April 6, 2023): 478–84. http://dx.doi.org/10.3762/bjnano.14.38.
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A mid-infrared (MIR) focusing grating coupler (FGC) with a single circular arc element (CAE) in the front of the gratings based on a germanium-on-silicon (Ge-on-Si) platform is designed and demonstrated. It can be used equivalently to a traditional FGC with all-focusing gratings. By optimizing the structural parameters of the CAE, the combination of a tapered linear grating and the CAE can improve the coupling efficiency to 8.61%, which is twice as large as that of the traditional MIR grating couplers. To the best of our knowledge, it is the highest coupling efficiency in a full-etch grating coupler based on Ge-on-Si. Moreover, the proposed grating coupler can be used for refractive index (RI) sensing, and the maximum sensitivity is 980.7 nm/RIU when the RI changes from 1 to 1.04. By comparing with traditional grating couplers requiring secondary etching, the proposed full-etch grating coupler structure can reduce the complexity of fabrication and can provide a prospective platform for MIR photonic integration and photonic biosensor detection.
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Su, Shuenn-Kung, Feng-Ping Lin, Chih-Feng Huang, Chien-Hsing Lu, and Jem-Kun Chen. "Coordination between Surface Lattice Resonances of Poly(glycidyl Methacrylate) Line Array and Surface Plasmon Resonances of CdS Quantum on Silicon Surface." Polymers 11, no. 3 (March 25, 2019): 558. http://dx.doi.org/10.3390/polym11030558.
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In this work, a unique hybrid system is proposed for one-dimensional gratings comprising of poly(glycidyl methacrylate) (PGMA) brushes and CdS quantum dots (CQDs). Generally, the emission of QDs is too weak to be observed in a dry state. Plasmonic resonances of the grating structures can be used to enhance the light emission or absorption of CQDs. The interaction between PGMA plasmonic nanostructures and inorganic CQDs plays a crucial role in engineering the light harvest, notably for optoelectronic applications. Extinction measurements of the hybrid system consisting of a PGMA grating and CQDs are reported. We designed one-dimensional gratings with various resolutions to tune the absorptance peaks of grating. PGMA grating grafted from a 1.5 µm resolution of trench arrays of photoresist exhibited absorptance peak at 395 nm, close to the absorption peak of CQDs, resulting in the photoluminescence enhancement of CQDs on the grating due to high charge carriers’ recombination rate. Generally, the emission of quantum dots occurs under irradiation at characteristic wavelengths. Immobilizing QDs on the grating facilitates the emission of QDs under irradiation of full-wavelength light. Furthermore, the PGMA gratings with CQDs were immersed in various solvents to change the geometries resulting the shift of absorptance peak of grating. The proposed method could be applied for sensing the nature of the surrounding media and vice versa, as well as for various media of solvents.
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Mateev, G., L. Nedelchev, D. Nazarova, L. Nikolova, B. Ivanov, V. Strijkova, and E. Stoykova. "Polarization properties of two-dimensional polarization holographic gratings inscribed in azopolymer thin films." Journal of Physics: Conference Series 2487, no. 1 (May 1, 2023): 012011. http://dx.doi.org/10.1088/1742-6596/2487/1/012011.
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Abstract Azopolymers are efficient photoanisotropic materials and for this reason are commonly used for inscription of polarization-selective diffraction gratings by polarization holography. More often however, the characteristics of one-dimensional (1D) gratings are studied. Here, we present real time diffraction efficiency kinetics and polarization properties of two-dimensional (2D) polarization holographic gratings, each of them obtained by overlapping two perpendicular 1D gratings. The gratings are consecutively inscribed using as recording medium the azopolymer poly[1-[4-(3-carboxy-4-hydroxyphenylazo)benzenesulfonamido]-1,2-ethanediyl, sodium salt], or PAZO. To record the gratings, He-Cd laser (λ = 442 nm) was used with left and right circular polarizations (LCP and RCP) of the recording beams. Our results show that the volume polarization grating has lower influence on the polarization properties of the 2D grating than the surface relief scalar grating.
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Li, Y., and Li Jiang Zeng. "Analyzing the Grating Profile Parameters Based on Scanning-Electron Microscope Images." Key Engineering Materials 381-382 (June 2008): 299–300. http://dx.doi.org/10.4028/www.scientific.net/kem.381-382.299.
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Measuring grating profiles is very helpful for the analysis of specifications of gratings and improvement of grating fabrication techniques. We analyzed grating grooves by digitizing the scanning-electron microscope (SEM) images. Some kinds of filter and arithmetic were developed to extract the contour line of grating profile. In order to analyze the diffraction efficiency affected by the shape of grating profile, the calculated diffraction efficiency based on the SEM image and measured diffraction efficiency based on experiment was compared and analyzed.
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Yang, Yin Fei, Ye Cao, Zheng Rong Tong, and Xiu Feng Yang. "Experimental Study on Etched Micro-Structured Fiber Bragg Grating." Applied Mechanics and Materials 130-134 (October 2011): 4061–64. http://dx.doi.org/10.4028/www.scientific.net/amm.130-134.4061.
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Here based on the combination of Comsol and the transmission matrix of Matlab, the spectrums of etched micro-structured gratings are simulated and two different modes of etched micro-structured fiber gratings are made in experiment. Etched micro-structured fiber grating is formed by using hydrofluoric acid (HF)-based wet chemical etching or femtosecond laser etching. This can reduce the clad layer along a standard grating partly or entirely and change the transmission feature of the grating. As a result, the thinner cladding layer changes the core propagation features and thus induces a phase delay on the guided mode, leading to the formation of a defect state inside the original grating band-gap in agreement with the phase shift grating theory. The defect state is mainly influenced by three parameters: the length and depth of the perturbation and the surrounding refractive index (SRI).
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Wang, Bo, Yu-Ting Wang, Fu-Ting Yi, Tian-Chong Zhang, Jing Liu, and Yue Zhou. "Fabrication of absorption gratings with X-ray lithography for X-ray phase contrast imaging." International Journal of Modern Physics B 32, no. 13 (May 11, 2018): 1850163. http://dx.doi.org/10.1142/s0217979218501631.
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Grating-based X-ray phase contrast imaging is promising especially in the medical area. Two or three gratings are involved in grating-based X-ray phase contrast imaging in which the absorption grating of high-aspect-ratio is the most important device and the fabrication process is a great challenge. The material with large atomic number Z is used to fabricate the absorption grating for excellent absorption of X-ray, and Au is usually used. The fabrication process, which involves X-ray lithography, development and gold electroplating, is described in this paper. The absorption gratings with 4 [Formula: see text]m period and about 100 [Formula: see text]m height are fabricated and the high-aspect-ratio is 50.
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Zaidi, Qasim, and W. L. Sachtler. "Motion Adaptation from Surrounding Stimuli." Perception 20, no. 6 (December 1991): 703–14. http://dx.doi.org/10.1068/p200703.
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When a narrow uniform gap was surrounded by a moving grating, the gap appeared as a grating in the opposite phase to that of the surround, moving in the same direction with the same speed. Contrast thresholds for moving test-gratings placed in the region of the uniform gap were found to be elevated after prolonged viewing of this pattern, thus demonstrating the existence of motion adaptation in a retinal region surrounded by, but not covered by, a moving pattern. The amplitude of the moving induced-grating was measured by nulling with a real grating moving in the same direction and with the same speed as the surround. When the speed of the inducing grating was varied, the amplitude of the induced effect did not correlate with the magnitude of the threshold elevation. Therefore, it is unlikely that motion adaptation in the uniform gap was due to induced gratings. In some conditions, the adaptation effect of surrounding gratings was no less than the adaptation effect of gratings covering the test region. This result rules out an explanation involving scattered light, and indicates that motion adaptation occurs at a later stage than that consisting of simple motion mechanisms which confound the contrast and velocity of a moving stimulus.
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Tang, Min Jin, Hui Min Xie, Jian Guo Zhu, Peng Wan Chen, Qing Ming Zhang, and Xiao Jun Li. "A New Moiré Grating Fabrication Technique Using Hot Embossing Lithography." Applied Mechanics and Materials 83 (July 2011): 7–12. http://dx.doi.org/10.4028/www.scientific.net/amm.83.7.
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Moiré grating is a basic optical component, and can be used in various moiré methods. The conventional grating fabrication technology is based on photolithography and holographic interferometry, however, it requires complex optical components and is very difficult to put into practice. In this study, nanoimprint lithography (NIL), or rather, hot embossing lithography (HEL), is proposed for producing high frequency grating. Compared with silicon mold, holographic moiré grating mold costs less and is not easy to break, thus is chosen to be the mold in HEL. Using this mold and the hot embossing system, the grating structure can be transferred to the polymer after HEL process. Through a number of experiments, the process parameters were optimized and gratings were successfully fabricated. The multi-scale morphology of the fabricated gratings was then characterized by scanning electron microscope (SEM), atomic force microscope (AFM) and moiré interferometry. The microscale images observed by AFM and SEM show the regulate dots with equal spacing and the macroscale moiré patterns illuminate the excellent qualities of fabricated grating in a large area. The successful experimental results demonstrate the feasibility of the grating fabricated by HEL for the moiré measurement.
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SERGEEV, S. A., M. S. IOVU, and A. YU MESHALKIN. "SUPERIMPOSED EQUALLY ORIENTED DIFFRACTION GRATINGS FORMED IN As2S3 FILMS." Chalcogenide Letters 17, no. 1 (January 2020): 25–31. http://dx.doi.org/10.15251/cl.2020.171.25.
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Surface relief diffraction structures composed of two or three superimposed unidirectional gratings with unequal grating periods were produced using the electron beam recording and subsequent chemical etching. Diffraction patterns produced by different diffraction structures were studied. In addition to the main diffracted beams the low-intensity “ghost” diffracted beams were created by some grating structures. Their appearance was caused by a difference in spatial frequency between gratings and by summation of spatial frequencies as well. The calculated grating periods corresponding to “ghost” diffracted beams were found to agree well with those determined from diffraction patterns.
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Tutt, James H., Randall L. McEntaffer, Hannah Marlowe, Drew M. Miles, Thomas J. Peterson, Casey T. DeRoo, Frank Scholze, and Christian Laubis. "Diffraction Efficiency Testing of Sinusoidal and Blazed Off-Plane Reflection Gratings." Journal of Astronomical Instrumentation 05, no. 03 (September 2016): 1650009. http://dx.doi.org/10.1142/s2251171716500094.
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Reflection gratings in the off-plane mount have the potential to enhance the performance of future high resolution soft X-ray spectrometers. Diffraction efficiency can be optimized through the use of blazed grating facets, achieving high-throughput on one side of zero-order. This paper presents the results from a comparison between a grating with a sinusoidally grooved profile and two gratings that have been blazed. The results show that the blaze does increase throughput to one side of zero-order; however, the total throughput of the sinusoidal gratings is greater than the blazed gratings, suggesting the method of manufacturing the blazed gratings does not produce precise facets. The blazed gratings were also tested in their Littrow and anti-Littrow configurations to quantify diffraction efficiency sensitivity to rotations about the grating normal. Only a small difference in the energy at which efficiency is maximized between the Littrow and anti-Littrow configurations is seen with a small shift in peak efficiency towards higher energies in the anti-Littrow case. This is due to a decrease in the effective blaze angle in the anti-Littrow mounting. This is supported by PCGrate-SX V6.1 modeling carried out for each blazed grating which predicts similar response trends in the Littrow and anti-Littrow orientations.
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Yu, W., D. Wu, X. Duan, and Y. Yi. "Subwavelength grating wideband reflectors with tapered sidewall profile." MRS Advances 1, no. 23 (December 21, 2015): 1683–91. http://dx.doi.org/10.1557/adv.2015.18.
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AbstractOne main difference between practical device and ideal design for subwavelength grating structure is the tapered sidewall profile of grating, which is normally obtained by the practical CMOS-compatible fabrication and etching process. Our work has investigated the impacts of tapered sidewall profile on the subwavelength grating wideband reflector characteristics. Both zero-contrast gratings (ZCG) and high- contrast gratings (HCG) are numerically investigated in detail and the results show a distinct differences of the impacts of tapered sidewall profile of grating. The simulation results reveal that this factor play a critical role in determining the reflection bandwidth, average reflectance, and the band edge. Our study has potential in guiding the utilization of subwavelength grating wideband reflector on application of a variety of nanophotonic devices and their integration, as well as to facilitate the design of the fabrication process on the control of tapered sidewall profile.
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Zhiwen, Wang, Gong Jinliang, Dong Aimei, and Cui Bo. "Mechanism analyzation of the effects of grating parameters on polarization transmission of single-layer nanowire gratings." Proceedings of the Institution of Mechanical Engineers, Part N: Journal of Nanomaterials, Nanoengineering and Nanosystems 232, no. 1 (December 5, 2017): 41–47. http://dx.doi.org/10.1177/2397791417744966.
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Using equivalent medium theory, surface plasma resonance theory and Fabry–Pérot resonance theory, transmission mechanism of single-layer nanowire polarizer is systematically analyzed. Concept of skin depth is used to explain the effect of grating material on polarization transmission. Two transmission minimum points in the curve of grating period versus transverse magnetic transmission are analyzed quantitatively. Effects of grating duty cycle, height and type on polarization transmission of single-layer nanowire polarizer are also analyzed. The requirements of designing single-layer sub-wavelength metal gratings with good polarization properties are given. The analysis of the transmission mechanism of sub-wavelength metal gratings will be helpful for the design and fabrication of the gratings with good polarization properties.
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Zhang, Guo Sheng, and Yan Xu. "Optimization Design of Cylinder Grating Used for Non-Contact Speed Measurement." Applied Mechanics and Materials 312 (February 2013): 95–100. http://dx.doi.org/10.4028/www.scientific.net/amm.312.95.
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In order to realize the detection of diffractive light after the image segmentation using cylinder grating, the parameters of a cylinder grating was optimized using the wave optics theory. By analyzing the relation of optical path length variation with the diffraction angle of single cylinder lens diffraction, and by Fraunhofer approximation, the analytical expressions of cylinder lens diffraction was given. By setting parameters to calculate and simulate, it was found that to increase the ratio of curvature radius and grating period could effectively reduce the spatial distribution of the diffraction light intensity. For the gratings that already exist, by reducing the ratio of refractive index of the gratings material and environment, the spatial light distribution of the grating could be reduced. If the cylinder grating period is too small, the overlap part of images segmentation light diffraction intensity will increase. But it occupies smaller proportion of the total light intensity. After the optimization design of cylinder grating, the results showed that it could be used for non-contact speed measurement in the range of some parameter.
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Babu, Sachin, and Jeong-Bong Lee. "Axially-Anisotropic Hierarchical Grating 2D Guided-Mode Resonance Strain-Sensor." Sensors 19, no. 23 (November 28, 2019): 5223. http://dx.doi.org/10.3390/s19235223.
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Guided-mode resonance strain sensors are planar binary gratings that have fixed resonance positions and quality factors decided by material properties and grating parameters. If one is restricted by material choices, the quality factor can only be improved by adjusting the grating parameters. We report a new method to improve quality factor by applying a slotting design rule to a grating design. We investigate this design rule by first providing a theoretical analysis on how it works and then applying it to a previously studied 2D solid-disc guided-mode resonance grating strain sensor design to create a new slotted-disc guided-mode resonance grating design. We then use finite element analysis to obtain reflection spectrum results that show the new design produces resonances with at least a 6-fold increase in quality factor over the original design and more axially-symmetric sensitivities. Lastly, we discuss the applicability of the slotting design rule to binary gratings in general as a means of improving grating performance while retaining both material and resonance position choices.
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Huang, Shubin, Zeyu Peng, Shi Rui, Renfu Zhang, Rui-Tao Wen, Xing Cheng, and Liang Guo. "Design and fabrication of diffraction grating with optimized efficiency for transient grating spectroscopy." Review of Scientific Instruments 93, no. 12 (December 1, 2022): 125112. http://dx.doi.org/10.1063/5.0116176.
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Transient grating spectroscopy (TGS) based on diffraction gratings is a powerful optical method for studying the transport of energy carriers such as phonons and electrons. The diffraction grating in a TGS system is a key component to form a large-area interference pattern, i.e., transient grating, and to study the mean free path distribution of energy carriers. In this work, a design method for polarization-insensitive diffraction gratings with periods in the range 2–50 µm for TGS by a combination of rigorous coupled wave analysis and genetic algorithm was discussed. The method was tested for pump/probe wavelength of 515/532 or 1030/808 nm. Each ±1st diffraction order carries 35%–40% of the incident energy and the diffraction efficiencies of the other orders are lower than 10%. The optimized diffraction gratings were fabricated by a combination of photolithography and inductively coupled plasma etching, with the processing parameters introduced in detail, and their optical characteristics were evaluated. Finally, as a demonstration, the diffraction gratings for 1030/808 nm were applied to TGS to study the thermal transport properties of Ge. This work provides a useful guide for future applications and the development of TGS.
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Yavorskiy, Dmitriy, Maria Szoła, Krzysztof Karpierz, Rafał Rudniewski, Rafał Bożek, Grzegorz Karczewski, Tomasz Wojtowicz, Jerzy Wróbel, and Jerzy Łusakowski. "Polarization of Magnetoplasmons in Grating Metamaterials Based on CdTe/CdMgTe Quantum Wells." Materials 13, no. 8 (April 11, 2020): 1811. http://dx.doi.org/10.3390/ma13081811.
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Grating metamaterials were fabricated with electron beam lithography on CdTe/CdMgTe modulation doped structures with two non-interacting quantum wells. Two types of samples were studied: with etched gratings and with gratings formed by deposition of Au stripes. The polarization properties at THz frequencies of the gratings were determined at room temperature. It was shown that Au gratings formed a linear polarizer, while etched gratings did not polarize THz radiation. Transmission of circularly polarized THz radiation at low temperatures through a sample with no grating showed a strongly circularly polarized cyclotron resonance transition. Transmission of this radiation through a sample with an etched grating showed a magnetoplasmon transition that was almost perfectly linearly polarized. We concluded that magnetoplasmons in metamaterials with etched gratings are linearly polarized excitations, possibly with a small contribution of a circular component. This work opens the possibility of the detailed study of the polarization of magnetoplasmons, which has not been explored in the past.
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Huang, Li Qun, and Guang Yang. "Optical Spectrum Characteristics of Phase-Only Sampled Chirp Gratings with Manufacturing Errors." Applied Mechanics and Materials 263-266 (December 2012): 1067–70. http://dx.doi.org/10.4028/www.scientific.net/amm.263-266.1067.
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Due to strong coupling among multi-channels of phase-only sampled gratings, the effects of manufacturing errors on sampled grating are different from fiber gratings with a single reflection peak. The influence was investigated by numerical simulation. When group delay and reflectivity ripples are caused by random phase and amplitude errors, inside a grating channel, the ripple amplitude at short wavelength is larger than the one at long wavelength, and this phenomenon was qualitatively explained using the principle that the reflecting position varies with the wavelength of incident light in a chirp grating. The sub-grating length of the transfer matrix method, which is decided by the accuracy of phase mask and UV writing, exerts an influence on the ripple amplitude. For multi-channel fiber gratings, stitch error impairs the periodicity of sampling function, so this kind of fabrication error leads to unequal performance reduction in different channels, and the reduction is more serious for channels at two sides.
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KUO, JU-NAN. "LENGTH AND WIDTH EFFECTS OF METAL FILMS ON STRESS-INDUCED BENDING OF SURFACE MICROMACHINED CANTILEVER CURVED GRATING." Surface Review and Letters 19, no. 01 (February 2012): 1250001. http://dx.doi.org/10.1142/s0218625x12500011.
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In this study, the length and width effects of metal films on the stress-induced bending of a surface micromachined cantilever curved grating are systematically investigated. A characterization of cantilever curved gratings with various lengths and widths was conducted to observe out-of-plane deformation. A finite element model was established to analyze the deformation. Finite element analysis and experimental results indicate that the commonly used beam theory formula for predicting the deformation of surface micromachined cantilever curved gratings is not valid for these devices. Experiments show that the shape of a cantilever curved grating and residual stress have a close relationship. As the length increases, the residual stress of the metal increases, resulting in a larger out-of-plane deformation of the cantilever curved grating. The tip deflection gradually decreases as the length-to-width ratio of the cantilever curved grating increases. A more reliable shape design of metal films on the stress-induced bending of surface micromachined cantilever curved gratings can thus be achieved.
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Lubov, Maxim, and Leonid Goray. "High-efficiency X-ray multilayer-coated blazed gratings with shifted boundaries." Journal of Synchrotron Radiation 26, no. 5 (July 19, 2019): 1539–45. http://dx.doi.org/10.1107/s1600577519006337.
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A new design for a high-efficiency multilayer-coated blazed X-ray grating with horizontal-shifted (non-conformal) boundary profiles is proposed. The investigation of the grating design is carried out using an integrated approach based on rigorous numerical calculations of light diffraction by gratings with realistic boundary profiles obtained from simulations of multilayer grating growth. By varying the incidence angle of the deposition flux, one can set the direction and magnitude of the boundary profile shifts over a wide range of values. It is shown that the diffraction efficiency of the blazed gratings with shifted boundary profiles may be substantially higher than the efficiency of gratings with conformal boundaries, which are, moreover, much more difficult to produce. High-efficiency gratings with shifted boundaries can be obtained when the deposition is mainly on the blaze facet with a high inclination of the deposition flux, as opposed to widely used near-normal deposition methods. The maximum absolute efficiency of a W/B4C 2500 mm−1 grating with a blaze angle of 1.76° and an anti-blaze angle of 20°, working at a blaze wavelength of 1.3 nm and having shifted realistic boundary profiles, obtained using our integrated approach is 23.3%, while that of a grating with the ideal (triangular) boundary profile and the same shifts is 25.3%, and that of an ideal conformal profile is only 22.2%. The maximum absolute efficiency of 40.2% of a 2500 mm Cr/C grating with a blaze angle of 1.05° and a realistic anti-blaze angle of 10°, working at a blaze wavelength of 0.83 nm and having ideal shifted boundaries, is higher than the maximum efficiency of the similar grating having ideal conformal boundaries with a non-realistic anti-blaze angle of 80°.
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Zhang, S., J. W. Zhang, Y. Zhou, J. Q. Su, X. Wang, B. Deng, and D. X. Hu. "Analysis of wavefront effects for large-aperture tiled-grating compressor." Laser and Particle Beams 36, no. 1 (January 29, 2018): 84–91. http://dx.doi.org/10.1017/s0263034617000878.
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AbstractMonolithic large-aperture diffraction grating tiling is desired to increase the output capability of multi-kilojoule petawatt laser facilities. However, the wavefront errors of input pulse and gratings will degrade the focal spot quality and the compressibility of the output pulse. In this work, the effects of wavefront error of input pulse, deformation and wave aberration of the grating for the large-aperture tiled-grating compressor are investigated theoretically. A series of numerical simulations are presented to discuss the changing trends of focal spot energy caused by wavefront error of input pulse and obtain the error tolerance for specific goals. The influences of coating stress and the wave aberration of holographic exposure gratings on the diffraction wavefront are also discussed. Some advice is proposed for improving the performance of large-aperture tiled-grating. This work paves the way for the design of practical large-aperture tiled-grating compressor for ultrahigh intensity laser facilities in the future.
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Ishihara, M. "Effect of Luminance Contrast on the Motion Aftereffect." Perception 26, no. 1_suppl (August 1997): 191. http://dx.doi.org/10.1068/v970311.
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The effects of luminance contrast and spatial frequency in the transient channel were investigated by making use of the motion aftereffect (MAE) caused by adaptation to a drifting sinusoidal grating. Two experiments were performed. The PSE of the velocity was measured as an index of the MAE. The adapting grating was made to drift at a velocity of 2.28 deg s−1 and its spatial frequency was 0.8, 1.6, or 3.2 cycles deg−1. In the first experiment, the MAE caused by a luminance contrast grating or an equiluminous chromatic grating was measured. In the second experiment, luminance contrast gratings were used to measure the effect of the contrast differences between adapting and test gratings. The largest MAE was observed when a low-luminance-contrast grating or an equiluminous chromatic grating was presented as test stimulus after adaptation to a high-luminance-contrast grating in the low-spatial-frequency condition. Generally, the MAE increased with increasing adapting contrast and with decreasing test contrast or spatial frequency. Little MAE was observed at high test contrasts. The results may be explained by assuming that activity in the sustained channel (or parvocellular pathway) inhibits activity in the transient channel (or magnocellular pathway) owing to the domination of sustained channel activity when the test is a static high-luminance-contrast grating providing much information about position and form.
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Cao, Jianjun, Yuan Sun, Yan Kong, and Weiying Qian. "The Sensitivity of Grating-Based SPR Sensors with Wavelength Interrogation." Sensors 19, no. 2 (January 19, 2019): 405. http://dx.doi.org/10.3390/s19020405.
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In this paper, we derive the analytical expression for the sensitivity of grating-based surface plasmon resonance (SPR) sensors working in wavelength interrogation. The theoretical analysis shows that the sensitivity increases with increasing wavelength and is saturated beyond a certain wavelength for Au and Ag gratings, while it is almost constant for Al gratings in the wavelength range of 500 to 1000 nm. More importantly, the grating period (P) and the diffraction order (m) dominate the value of sensitivity. Higher sensitivity is possible for SPR sensors with a larger grating period and lower diffraction order. At long wavelengths, a simple expression of P/|m| can be used to estimate the sensor sensitivity. Moreover, we perform experimental measurements of the sensitivity of an SPR sensor based on an Al grating to confirm the theoretical calculations.
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Liu, Xuan, Lisa Samfaß, Kevin Kolpatzeck, Lars Häring, Jan C. Balzer, Martin Hoffmann, and Andreas Czylwik. "Terahertz Beam Steering Concept Based on a MEMS-Reconfigurable Reflection Grating." Sensors 20, no. 10 (May 19, 2020): 2874. http://dx.doi.org/10.3390/s20102874.
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With an increasing number of applications of terahertz systems in industrial fields and communications, terahertz beamforming and beam steering techniques are required for high-speed, large-area scanning. As a promising means for beam steering, micro-electro-mechanical system (MEMS)-based reflection gratings have been successfully implemented for terahertz beam control. So far, the diffraction grating efficiency is relatively low due to the limited vertical displacement range of the reflectors. In this paper, we propose a design for a reconfigurable MEMS-based reflection grating consisting of multiple subwavelength reflectors which are driven by 5-bit, high-throw electrostatic actuators. We vary the number of the reflectors per grating period and configure the throw of individual reflectors so that the reflection grating is shaped as a blazed grating to steer the terahertz beam with maximum diffraction grating efficiency. Furthermore, we provide a mathematical model for calculating the radiation pattern of the terahertz wave reflected by general reflection gratings consisting of subwavelength reflectors. The calculated and simulated radiation patterns of the designed grating show that we can steer the angle of the terahertz waves in a range of up to ± 56.4 ∘ with a maximum sidelobe level of −10 dB at frequencies from 0.3 THz to 1 THz.
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Bex, P. J., F. A. J. Verstraten, and I. Mareschal. "Temporal and Spatial Frequency Tuning of the Flicker Motion Aftereffect." Perception 25, no. 1_suppl (August 1996): 12. http://dx.doi.org/10.1068/v96l0804.
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The motion aftereffect (MAE) was used to study the temporal-frequency and spatial-frequency selectivity of the visual system at suprathreshold contrasts. Observers adapted to drifting sine-wave gratings of a range of spatial and temporal frequencies. The magnitude of the MAE induced by the adaptation was measured with counterphasing test gratings of a variety of spatial and temporal frequencies. Independently of the spatial or temporal frequency of the adapting grating, the largest MAE was found with slowly counterphasing test gratings (∼0.125 – 0.25 Hz). For slowly counterphasing test gratings (<∼2 Hz), the largest MAEs were found when the test grating was of similar spatial frequency to that of the adapting grating, even at very low spatial frequencies (0.125 cycle deg−1). However, such narrow spatial frequency tuning was lost when the temporal frequency of the test grating was increased. The data suggest that MAEs are dominated by a single, low-pass temporal-frequency mechanism and by a series of band-pass spatial-frequency mechanisms at low temporal frequencies. At higher test temporal frequencies, the loss of spatial-frequency tuning implicates separate mechanisms with broader spatial frequency tuning.
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Gao, Xiaoyu, Shengjie Cao, Yongqiu Zheng, and Jiandong Bai. "A Compact Fabry–Pérot Acoustic Sensor Based on Silicon Optical Waveguide Bragg Gratings." Photonics 10, no. 8 (July 25, 2023): 861. http://dx.doi.org/10.3390/photonics10080861.
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No membranous optical sensors have excellent development prospects in aerospace and other industrial fields due to their small size and anti-electromagnetic interference. Here, we proposed a novel Fabry–Pérot (FP) cavity acoustic sensor based on silicon optical waveguide Bragg gratings. The FP cavity consists of two Bragg gratings written on the silicon-based optical waveguide and a miniature air groove. When the sound signal acts on the miniature air groove, the sound pressure changes the density of air molecules near the waveguide grating’s evanescent field, causing variation in the air’s refractive index. This results in a shift in the reflection spectrum of the FP cavity to detect the sound signal. The effects of the grating period, grating pitch quantity, and groove depth of the FP cavity on acoustic sensing were studied. The modelling predicts that the sensing sensitivity could be 0.4 nm/Pa. Theoretically, the compact self-designed acoustic sensor can withstand temperatures above 800 °C. Therefore, it has significant potential applications in precision measurement in high-temperature and high-pressure environments.