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Showing papers on "Diffraction efficiency published in 2020"


Journal ArticleDOI
TL;DR: This work introduces and experimentally demonstrates a new training scheme that significantly increases the robustness of diffractive networks against 3D misalignments and fabrication tolerances in the physical implementation of a trained diffractive network.
Abstract: As an optical machine learning framework, Diffractive Deep Neural Networks (D2NN) take advantage of data-driven training methods used in deep learning to devise light-matter interaction in 3D for performing a desired statistical inference task. Multi-layer optical object recognition platforms designed with this diffractive framework have been shown to generalize to unseen image data achieving e.g., >98% blind inference accuracy for hand-written digit classification. The multi-layer structure of diffractive networks offers significant advantages in terms of their diffraction efficiency, inference capability and optical signal contrast. However, the use of multiple diffractive layers also brings practical challenges for the fabrication and alignment of these diffractive systems for accurate optical inference. Here, we introduce and experimentally demonstrate a new training scheme that significantly increases the robustness of diffractive networks against 3D misalignments and fabrication tolerances in the physical implementation of a trained diffractive network. By modeling the undesired layer-to-layer misalignments in 3D as continuous random variables in the optical forward model, diffractive networks are trained to maintain their inference accuracy over a large range of misalignments; we term this diffractive network design as vaccinated D2NN (v-D2NN). We further extend this vaccination strategy to the training of diffractive networks that use differential detectors at the output plane as well as to jointly-trained hybrid (optical-electronic) networks to reveal that all of these diffractive designs improve their resilience to misalignments by taking into account possible 3D fabrication variations and displacements during their training phase.

63 citations


Journal ArticleDOI
24 Jul 2020-ACS Nano
TL;DR: Leveraging on the advantages of additive manufacturing inherent to TPL, the 3D printed optical devices can be applied for precise wavefront shaping, with great potential in all-optical machine learning, virtual reality, motion sensing, and medical imaging.
Abstract: Diffractive optical elements (DOEs) are widely applied as compact solutions to generate desired optical patterns in the far field by wavefront shaping. They consist of microscopic structures of varying heights to control the phase of either reflected or transmitted light. However, traditional methods to achieve varying thicknesses of structures for DOEs are tedious, requiring multiple aligned lithographic steps each followed by an etching process. Additionally, the reliance on photomasks precludes rapid prototyping and customization in manufacturing complex and multifunctional surface profiles. To achieve this, we turn to nanoscale 3D printing based on two-photon polymerization lithography (TPL). However, TPL systems lack the precision to pattern diffractive components where subwavelength variations in height and position could lead to observable loss in diffraction efficiency. Here, we employed a lumped TPL parametric model and a workaround patterning strategy to achieve precise 3D printing of DOEs using optimized parameters for laser power, beam scan speed, hatching distance, and slicing distance. In our case study, millimeter scale near-perfect Dammann gratings were fabricated with measured diffraction efficiencies near theoretical limits, laser spot array nonuniformity as low as 1.4%, and power ratio of the zero-order spot as low as 0.4%. Leveraging on the advantages of additive manufacturing inherent to TPL, the 3D-printed optical devices can be applied for precise wavefront shaping, with great potential in all-optical machine learning, virtual reality, motion sensing, and medical imaging.

50 citations


Journal ArticleDOI
Jinpeng Yuan1, Shichao Dong1, Chaohua Wu1, Lirong Wang1, Liantuan Xiao1, Suotang Jia1 
TL;DR: A novel tunable all-optical tunable grating is realized experimentally in a V+Ξ configuration coherent rubidium thermal vapor and promises to be the new driving force in the advancement of all-Optical communications and information technology.
Abstract: A novel tunable all-optical grating is realized experimentally in a V+Ξ configuration coherent rubidium thermal vapor. This new energy level structure employs a Rydberg level as the uppermost level and contains two typical electromagnetically induced transparency energy level configurations with the same probe field. Compared with the traditional V-type three-level grating, a significant improvement of the diffraction efficiency of this novel grating was observed. Its improvement was then also demonstrated experimentally by the transition spectrum and theoretically by a comprehensive simulation. The diffraction efficiency gain introduced by the control laser field was tuned with several experimental parameters, such as the atomic density and the control field intensity. And the maximum enhancement rate of first-order diffraction efficiency is proved to be as high as 30%. Such a novel all-optical tunable grating promises to be the new driving force in the advancement of all-optical communications and information technology.

38 citations


Journal ArticleDOI
03 Dec 2020
TL;DR: This mini-review starts from the photoalignment (PA) process and then dives into device structures and performances, to understand the interactions between the PA mechanism and LC molecules helps to optimize the device performance for novel optical systems.
Abstract: Liquid-crystal (LC)-based ultrathin flat optical elements (FOEs) exhibit several attractive properties, such as a high degree of optical tunability, strong polarization selectivity, nearly 100% diffraction efficiency, and a simple fabrication process. Investigating the alignment patterning of LC-FOEs to diversify their performance has attracted broad interest in the optics field. In this mini-review, we start from the photoalignment (PA) process and then dive into device structures and performances. By generating and recording the desired polarization fields on the PA layer, the LC molecules will follow the recorded patterns and establish the phase profiles for different functionalities, such as gratings and lenses. Because of the polarization dependency, LC-FOEs have found useful applications in near-eye displays. Understanding the interactions between the PA mechanism and LC molecules helps to optimize the device performance for novel optical systems.

36 citations


Journal ArticleDOI
Feng Zhou1, Jianyu Hua1, Jiacheng Shi1, Wen Qiao1, Linsen Chen1 
TL;DR: A multiview 3D display based on multi-level pixelated blazed gratings based on diffractive optics and metasurface is proposed that can present 3D images with ultrawide field of view and low crosstalk.
Abstract: Multiview 3D display can reveal wondrous information of a 3D image without any visual aids. Therefore, it has great potential in many applications, such as education, game, training, and design. Among all the multiview 3D display techniques, the one that is based on diffractive optics and metasurface can present 3D images with ultrawide field of view and low crosstalk. However, the brightness of diffractive multiview 3D display is limited by the diffraction efficiency. Moreover, the low fabrication efficiency and high cost limit the commercial development of 3D display based on metasurface. Here we propose a multiview 3D display based on multi-level pixelated blazed gratings. The period and orientation of each blazed grating in the view modulator is different to form a converged light field. A 4-view prototype was assembled by integrating the view modulator with a shadow mask for the modulation of light intensity. A 3D thoracic cage model was virtually projected within the viewing angle with minimum crosstalk. The light efficiency of the prototype is significantly improved to 60% for 4-level blazed gratings.

30 citations


Journal ArticleDOI
TL;DR: It is shown how the coherent control of metagratings through multiple wave excitations can provide new opportunities to achieve highly reconfigurable broadband metasurfaces with large diffraction efficiency, beyond the limitations of conventional approaches.
Abstract: Metasurfaces are 2D engineered structures with subwavelength granularity, offering a wide range of opportunities to tailor the impinging wavefront. However, fundamental limitations on their efficiency in wave transformation, associated with their deeply subwavelength thickness, challenge their implementation in practical application scenarios. Here, it is shown how the coherent control of metagratings through multiple wave excitations can provide new opportunities to achieve highly reconfigurable broadband metasurfaces with large diffraction efficiency, beyond the limitations of conventional approaches. Remarkably, energy distribution between the 0th and higher diffraction orders can be continuously tuned by changing the relative phase difference between two excitation waves, enabling coherent control, with added benefits of enhanced efficiency and bandwidth. This concept is demonstrated for a thin electric metagrating operating at terahertz frequencies, showing that coherent control can overcome several of the limitations of single-layer ultrathin metastructures, and extend their feasibility in various practical scenarios.

28 citations


Journal ArticleDOI
01 Jul 2020
TL;DR: In this paper, the authors describe the operation principles, discuss the optical properties, present the fabrication methods, and provide promising applications of liquid crystal-based reflective polarization volume grating for near-eye displays and novel photonic devices.
Abstract: Liquid crystal-based reflective polarization volume grating (PVG), also known as a linear Bragg–Berry phase optical element or a member of volume Bragg gratings (VBGs), is a functional planar structure with patterned orientation of optical axis. Due to the strong polarization selectivity, nearly 100% diffraction efficiency, large diffraction angle, and simple fabrication process, PVGs have found potential applications in novel photonic devices and emerging near-eye displays. In this review paper, we describe the operation principles, discuss the optical properties, present the fabrication methods, and provide promising applications of PVGs for near-eye displays and novel photonic devices.

27 citations


Journal ArticleDOI
TL;DR: In this article, the authors provide a comprehensive study of atomic Raman and Bragg diffraction when coupling to a pair of counterpropagating light gratings (double diffraction) or to a single one (single diffraction), and discuss the transition from one case to another in a retroreflective geometry as the Doppler detuning changes.
Abstract: We provide a comprehensive study of atomic Raman and Bragg diffraction when coupling to a pair of counterpropagating light gratings (double diffraction) or to a single one (single diffraction) and discuss the transition from one case to the other in a retroreflective geometry as the Doppler detuning changes. In contrast to single diffraction, double Raman loses its advantage of high diffraction efficiency for short pulses and has to be performed in a Bragg-type regime. Moreover, the structure of double diffraction leads to further limitations for broad momentum distributions on the efficiency of mirror pulses, making the use of (ultra)cold ensembles essential for high diffraction efficiency.

26 citations


Journal ArticleDOI
TL;DR: It is demonstrated that the diffraction of the crystal grating can be dynamically controlled via tuning the intensity and detuning of the standing-wave driving field or the concentration of Er3+ ion, and may provide a possibility for the active all-optical control of optical switching, routing and storage in fiber communication wavelengths.
Abstract: A coherently prepared Er3+-doped yttrium aluminum garnet (YAG) crystal with a four-level ionic configuration is exploited for realizing one-dimensional (1D) and two-dimensional (2D) electromagnetically induced gratings (EIGs). Owing to the probe gain induced by the incoherent pump, the diffraction efficiency of the crystal grating, especially the first-order diffraction, can be significantly improved via increasing the incoherent pumping rate or decreasing the probe detuning. The enhancement of the grating diffraction efficiency originates from the interference between the gain and phase gratings. It is also demonstrated that the diffraction of the crystal grating can be dynamically controlled via tuning the intensity and detuning of the standing-wave driving field or the concentration of Er3+ ion. More importantly, the probe energy of the diffraction side lobes around the central principle maximum is comparable to that of the first-order diffraction field for small driving intensity or large driving detuning. Our scheme may provide a possibility for the active all-optical control of optical switching, routing and storage in fiber communication wavelengths.

22 citations


Journal ArticleDOI
TL;DR: In this article, a vaccination strategy was proposed to improve the robustness of diffractive networks against 3D misalignments and fabrication tolerances in the physical implementation of a trained diffractive network.
Abstract: As an optical machine learning framework, Diffractive Deep Neural Networks (D2NN) take advantage of data-driven training methods used in deep learning to devise light-matter interaction in 3D for performing a desired statistical inference task. Multi-layer optical object recognition platforms designed with this diffractive framework have been shown to generalize to unseen image data achieving e.g., >98% blind inference accuracy for hand-written digit classification. The multi-layer structure of diffractive networks offers significant advantages in terms of their diffraction efficiency, inference capability and optical signal contrast. However, the use of multiple diffractive layers also brings practical challenges for the fabrication and alignment of these diffractive systems for accurate optical inference. Here, we introduce and experimentally demonstrate a new training scheme that significantly increases the robustness of diffractive networks against 3D misalignments and fabrication tolerances in the physical implementation of a trained diffractive network. By modeling the undesired layer-to-layer misalignments in 3D as continuous random variables in the optical forward model, diffractive networks are trained to maintain their inference accuracy over a large range of misalignments; we term this diffractive network design as vaccinated D2NN (v-D2NN). We further extend this vaccination strategy to the training of diffractive networks that use differential detectors at the output plane as well as to jointly-trained hybrid (optical-electronic) networks to reveal that all of these diffractive designs improve their resilience to misalignments by taking into account possible 3D fabrication variations and displacements during their training phase.

20 citations


Journal ArticleDOI
TL;DR: In this article, a cylindrical Fresnel lens with the surface roughness of 0.5-1.2 µm has been fabricated with a free electron laser at the wavelength of 141 µm and the laser-machined silicon retains its original transmittance.
Abstract: Precise microstructuring of silicon with short laser pulses is a promising technique for fabrication of kinoform diffractive optical elements (DOEs) for high-power THz radiation. Micrometer-scale surface roughness being a typical result of the silicon microstructuring with laser is an important factor reducing optical performance of the fabricated DOEs. We demonstrate here that proper optimization of the processing conditions under profiling of high-resistance silicon surface by 1 ps laser pulses at λ = 1.03 μm allows formation of cylindrical Fresnel lens with the surface roughness of 0.5–1.2 µm being one order of magnitude smaller than reported earlier. Testing of the fabricated lens with a free electron laser at the wavelength of 141 μm has shown that the laser-machined silicon retains its original transmittance. Diffraction efficiency (0.93 ± 0.06) and deviation of the laser intensity profile in the lens focus from the theoretical expectations have been evaluated. Additionally, influence of the surface roughness on transmittance of the laser-machined silicon in the wavelength range of 95–400 μm was studied by means of time domain spectroscopy.

Journal ArticleDOI
TL;DR: In this paper, a two-layer five-port diffraction grating with operation in transmission was designed and the accurate grating vector parameters were optimized using rigorous coupled-wave analysis (RCWA).
Abstract: In this paper, we report a two-layer five-port diffraction grating by a polarization-independent design under normal incidence. To be different from conventional five-port gratings, initially, we design a novel two-layer grating with operation in transmission. Next, we firstly design a polarization-independent grating with five-port splitting output. On the one hand, the accurate grating vector parameters are optimized using rigorous coupled-wave analysis (RCWA) approach. On the other hand, the inherent coupling mechanism happened in the grating region can be well explained by employing simplified modal method (SMM). More importantly, all reported conventional five-port beam splitter gratings were designed based on polarization dependent. Although they could obtain high diffraction efficiency for TE or TM polarization, it requires more complicated and time-consuming fabrication processes in practical grating applications. Thus, this work can open up a possible thought for designing polarization-independent multi-port beam splitter diffraction gratings.

Journal ArticleDOI
Bin Zhou1, Wei Jia1, Peng Sun1, Jin Wang1, Weicheng Liu1, Changhe Zhou1 
TL;DR: A reflective two-dimensional metal-dielectric grating based on cylindrical hole nano arrays with excellent polarization-independent high diffraction efficiency and a potential candidate as planar grating rulers for high precision multi-axis displacement measurement is proposed.
Abstract: In this paper, we propose a reflective two-dimensional (2D) metal-dielectric grating based on cylindrical hole nano arrays with excellent polarization-independent high diffraction efficiency. The effects of the geometrical parameters on the polarization characteristic and diffraction efficiency are studied. Optimized results show that the (-1, 0) order diffraction efficiency of transverse electric (TE) and transverse magnetic (TM) polarizations under Littrow mounting is 98.31% and 98.05% at 780 nm incident wavelength, and the diffraction efficiency equilibrium is 99.74%, which is a significant improvement over the previously reported 2D gratings. The high efficiency in both TE and TM polarizations makes it a potential candidate as planar grating rulers for high precision multi-axis displacement measurement. Moreover, the cylindrical hole-based structure performs well in manufacturing tolerances, which provides the possibility for practical applications.

Journal ArticleDOI
TL;DR: A new strategy for optimizing high-performance and wide-angle diffractive optical elements is introduced, offering unprecedented control over the power distribution among the desired diffraction orders with only low requirements with respect to computational power.
Abstract: Diffractive optical elements are ultra-thin optical components required for constructing very compact optical 3D sensors. However, the required wide-angle diffractive 2D fan-out gratings have been elusive due to design challenges. Here, we introduce a new strategy for optimizing such high-performance and wide-angle diffractive optical elements, offering unprecedented control over the power distribution among the desired diffraction orders with only low requirements with respect to computational power. The microstructure surfaces were designed by an iterative gradient optimization procedure based on an adjoint-state method, capable to account for application-dependent target functions while ensuring compatibility with existing fabrication processes. The results of the experimental characterization confirm the simulated tailored power distributions and optical efficiencies of the fabricated elements.

Journal ArticleDOI
Zhongwen Shen1, Yuning Zhang1, Liu Ao1, Yishi Weng1, Xiaohua Li1 
TL;DR: In this paper, a volume holographic waveguide display by dispersing gold nanoparticles (Au-NPs) in acrylate-based photopolymer is presented.
Abstract: We present a volume holographic waveguide display by dispersing gold nanoparticles (Au-NPs) in acrylate-based photopolymer. The diffractive bandwidth and diffraction efficiency (DE) of the volume holographic grating (VHG) applied for waveguide displays are characterized and analyzed through both the simulations and experiments. The results show that the wavelength bandwidth of the VHG can be enlarged to 30 nm with a corresponding refractive index modulation (RIM) increased to around 0.08 by dispersing the Au-NPs with a concentration of 0.012 g/ml into the acrylate-based photopolymer. Finally, the green monochromatic waveguide display system with 30° horizontal field of view (FOV) is realized.

Journal ArticleDOI
TL;DR: In this paper, a mold for a reflection grating with a periodicity of 400 nm and grooves resembling an asymmetric sawtooth was patterned in 130 nm thick poly(methyl methacrylate) resist on a silicon substrate over a 50 mm by 7.5 mm area.
Abstract: Future observatories utilizing reflection grating spectrometers for extreme ultraviolet (EUV) and soft X-ray (SXR) spectroscopy require high-fidelity gratings with both blazed groove facets and custom groove layouts that are often fanned or feature a slight curvature. While fabrication procedures centering on wet anisotropic etching in monocrystalline silicon produce highly efficient blazed gratings, the precision of a nonparallel groove layout is limited by the cubic structure of the silicon crystal. This motivates the pursuit of alternative techniques to grating manufacture, namely thermally activated selective topography equilibration (TASTE), which uses gray-scale electron-beam lithography to pattern multilevel structures in resist followed by an optimized polymer thermal reflow to smooth the 3D patterns into continuous surface relief profiles. Using TASTE, a mold for a reflection grating with a periodicity of 400 nm and grooves resembling an asymmetric sawtooth was patterned in 130 nm thick poly(methyl methacrylate) resist on a silicon substrate over a 50 mm by 7.5 mm area. This structure was coated with 15 nm of gold by electron-beam physical vapor deposition using titanium as an adhesion layer and then tested for EUV and SXR diffraction efficiency at beamline 6.3.2 of the Advanced Light Source synchrotron facility. Results demonstrate a quasi-blaze response characteristic of a 27 degree blaze angle with groove facets smooth to 1.5 nm rms. Absolute peak-order efficiency ranges from 75% to 25%, while total relative efficiency measures gap90% across the measured bandpass of 15.5 nm > lambda > 1.55 nm.

Journal ArticleDOI
TL;DR: In this paper, a compound metallic grating (a periodic metallic structure with more than one slit in each period) is proposed for anomalous reflection, which has an unprecedented near-to-unitary efficiency of 99.9%.
Abstract: Metagrating is a new concept for wavefront manipulation that, unlike phase gradient metasurfaces, does not suffer from low efficiency and also has a less complicated fabrication process. In this paper, a compound metallic grating (a periodic metallic structure with more than one slit in each period) is proposed for anomalous reflection. We propose an analytical method for analyzing the electromagnetic response of this grating. Closed-form and analytical expressions are presented for the reflection coefficients of zeroth diffracted order and also higher diffracted orders. The proposed method is verified against full-wave simulations and the results are in excellent agreement. Thanks to the geometrical asymmetry of compound metallic grating, it can be used for designing anomalous reflection at the normal incidence. Given analytical expressions for reflection coefficients, we design a perfect anomalous reflector for a TM polarized plane wave via transferring all the incident power to ( − 1) diffraction order . The structure designed in this study has an unprecedented near-to-unitary efficiency of 99.9%. Finally, a multi-element compound metallic grating is proposed for reflecting the normal incidence to angles of below 30°, which is a challenging accomplishment. This excellent performance of compound metallic grating shows its high potential for microwave and terahertz wavefront manipulation applications.

Journal ArticleDOI
TL;DR: Detailed numerical studies of several types of liquid crystal polarization gratings based on the rigorous coupled-wave analysis (RCWA) approach are performed, and the unique properties of Raman-Nath and Bragg gratings are investigated.
Abstract: Several types of liquid crystal polarization gratings (LCPGs) can be achieved depending on their molecular configurations and diffraction properties. We perform detailed numerical studies of these LCPGs based on the rigorous coupled-wave analysis (RCWA) approach. The unique properties of Raman-Nath and Bragg gratings are investigated, and how the transition between them influences the diffraction behaviors is explained. Two types of LCPGs, corresponding to the planar and the slanted director configurations, are compared in detail. The influence of gradient-pitch on the performance of reflection grating is also explored. Potential applications of these LCPGs for near-eye displays are emphasized.

Journal ArticleDOI
TL;DR: In this article, a new approach to fabricate diamond diffractive optical elements (DOEs) with continuous relief for powerful CO2 lasers is proposed and tested, which involves short-pulse laser microstructuring of a silicon wafer, which further is used as a substrate for polycrystalline diamond growth in a microwave plasma-assisted CVD process.

Journal ArticleDOI
TL;DR: A multiview holographic 3D display based on a phase-only blazed Fresnel-type diffractive optical element (FDOE) is proposed that can reconstruct converged views and virtual 3D scenes with an extended field of view (FOV) of 17 .

Journal ArticleDOI
TL;DR: An absorption-based polarization grating made of dichroic dye-doped polymerizable liquid crystal that manifest a polarization-sensitive diffraction efficiency over the absorption band of the employed dye material, based on theoretical analysis and experimental evidence is demonstrated.
Abstract: We demonstrate an absorption-based polarization grating made of dichroic dye-doped polymerizable liquid crystal. These gratings manifest a polarization-sensitive diffraction efficiency over the absorption band of the employed dye material, based on our theoretical analysis and experimental evidence. The spectral range can be easily tailored by varying the dye material. Since these gratings generate first-order diffracted beams with orthogonal circular polarizations, they can be utilized as key components in polarimetry systems. Meanwhile, due to their absorptive nature, these polarization gratings can function as LED-compatible polarization masks for photopatterning while fabricating various liquid crystal devices.

Journal ArticleDOI
TL;DR: A high-index contrast dielectric grating design for polarization-independent narrowband transmission filtering that provides a filter response that is simultaneously polarization independent and functional at normal incidence, overcoming limitations of 1D asymmetric gratings and 2D symmetric grating.
Abstract: We present a high-index contrast dielectric grating design for polarization-independent narrowband transmission filtering. A reduced symmetry hexagonal lattice allows coupling to symmetry-protected modes (bound states in the continuum) at normal incidence, enabling high-Q spectral peaks. The peak linewidth is tunable via degree of geometric symmetry reduction. Using diffraction efficiency calculations, we gain further insight into the design and physics of one-dimensional (1D) and two-dimensional (2D) asymmetric high contrast gratings. The grating design provides a filter response that is simultaneously polarization independent and functional at normal incidence, overcoming limitations of 1D asymmetric gratings and 2D symmetric gratings.

Journal ArticleDOI
26 Aug 2020-Polymers
TL;DR: This work demonstrates an electrically-tunable nematic liquid crystal (NLC) diffraction grating with a periodic electrode structure, and discusses the polarization properties of its diffraction.
Abstract: This work demonstrates an electrically-tunable nematic liquid crystal (NLC) diffraction grating with a periodic electrode structure, and discusses the polarization properties of its diffraction. The efficiency of the first-order diffraction can be gradually controlled by applying external electric fields cross the NLC, and the maximum diffraction efficiency of the first-order diffraction that can be obtained is around 12.5% under the applied voltage of 5.0 V. In addition to the applied electric field, the efficiency of the first-order diffraction can also vary by changing the polarized state of the incident beam. Antisymmetric polarization states with symmetrical intensities in the diffractions corresponding to the +1 and −1 order diffraction signals are also demonstrated.

Journal ArticleDOI
Ting Li1, Yang Yang1, Liu Xinyang1, Yan Wu1, Yuan Zhou1, Sijia Huang1, Li Xiaochun, Huihui Huang1 
TL;DR: This Letter employs photo-aligned liquid crystals to record a flat lens pattern through a simple exposure method to produce a large focal length Pancharatnam-Berry lens with a film thickness of 2µm without using expensive equipment and proposes an improved two-dimensional optical edge detection design.
Abstract: In this Letter, we employ photo-aligned liquid crystals to record a flat lens pattern through a simple exposure method to produce a large focal length Pancharatnam-Berry (PB) lens with a film thickness of 2µm without using expensive equipment. This PB lens with a focal length of 240.6 m (at 532 nm) can transmit up to 97% across visible wavelengths and maintain high diffraction efficiency (>90%). An improved two-dimensional optical edge detection design based on this lens is proposed. We experimentally demonstrate the integrity and high efficiency of edge information that may play an important role in the application of image processing and high-contrast microscopy.

Journal ArticleDOI
TL;DR: A large area (2×2 mm2) high aspect ratio (13:1) diamond grating on a diamond plate is fabricated, which resulted in a high splitting efficiency (30%) and Tunable efficiency was obtained via tilting the grating with respect to the x-ray beam.
Abstract: X-ray free electron lasers (XFELs) provide femtosecond high-power x-ray beams with high spatial coherence, resulting in numerous influential discoveries. Diffractive optics allow for the easy manipulation and measurement of an x-ray beam’s wavefront and enable the realization of complex designed properties and specifications. For example, phase gratings can be used as x-ray beam splitters to enable beam sharing by multiple end stations or in-situ beam monitoring, including spectrum and wavefront measurements. Wavefront preservation and high efficiency and survivability under high power are requirements for such beam splitters. Diamond is the most suitable choice for phase grating fabrication, due to its high thermal conductivity that enables it to survive high average power XFEL beams. We have fabricated a large area (2×2 mm2) high aspect ratio (13:1) diamond grating on a diamond plate. Testing was performed at 9.5 keV and resulted in a high splitting efficiency (30%). Tunable efficiency was obtained via tilting the grating with respect to the x-ray beam. Wavefront fidelity of the split beams were measured to less than λ/100 using a Talbot wavefront sensor.

Journal ArticleDOI
Chao Zhou1, Chuan He1, S. Yan1, Yu-Hang Ji1, Lin Zhou1, Jin Wang1, Mingsheng Zhan1 
TL;DR: Combining the ±1st order diffraction, laser signals with up to 10 GHz frequency difference can be obtained, which fulfill most frequency shift requirements of laser cooling and coherent manipulation experiments with alkali metal atoms.
Abstract: We demonstrate a novel laser frequency shift scheme using a 12-pass 350-MHz acousto-optic modulator (AOM). This AOM system shows better performance compared to ordinary acousto-optic modulation schemes. The frequency of the incident laser beam is shifted by 4.2 GHz with the total diffraction efficiency as high as 11%, and the maximum frequency shift is 5 GHz. Combining the ±1st order diffraction, laser signals with up to 10 GHz frequency difference can be obtained, which fulfill most frequency shift requirements of laser cooling and coherent manipulation experiments with alkali metal atoms.

Journal ArticleDOI
TL;DR: In this paper, the quantization effects when displaying blazed phase diffraction gratings in such devices were investigated. But the effects were only applied to devices with a phase-dynamic range as large as 10π.

Journal ArticleDOI
TL;DR: In this article, the authors investigated the effect of applied dc electric field (E0) on the diffraction efficiency of undoped Bi12TiO20 crystal at 1064nm.

Journal ArticleDOI
TL;DR: In this article, a multilayer dielectric reflection gratings of 1300 line/mm for spectral beam combining were designed and fabricated for a single-antenna system with a duty cycle much greater than 0.5, and the measured polarization-averaged diffraction efficiency of the fabricated gratings was greater than 97% in the wavelength range of 1050nm-1080nm.

Journal ArticleDOI
TL;DR: It is demonstrated that a proper choice of the multilayer d-spacing allows to design grating with the diffraction efficiency close to the maximal possible one throughout the tender X-ray range (E∼1-5 keV).
Abstract: The problem of X-ray diffraction from multilayer-coated blazed diffraction gratings is analyzed. Invalidity of the conventional condition of maximal diffraction efficiency observed in previous experiments is explained theoretically. This is attributed to two factors: contribution of anti-blaze facets to diffraction efficiency and effect of strongly asymmetric diffraction. We demonstrate that a proper choice of the multilayer d-spacing allows to design grating with the diffraction efficiency close to the maximal possible one throughout the tender X-ray range (E∼1-5 keV). An optimization procedure is suggested for the first time to choose the optimal grating parameters and the operation diffraction order to obtain a high fix-focus constant and high diffraction efficiency simultaneously in a wide spectral range.