Showing papers on "Diffraction efficiency published in 2010"
TL;DR: Diffractive waveplates exhibit the high diffraction efficiency of Bragg gratings in micron-thick material layers as discussed by the authors, which is similar to the one we use in this paper.
Abstract: Diffractive waveplates exhibit the high diffraction efficiency of Bragg gratings in micron-thick material layers.
158 citations
TL;DR: In this paper, an atomic phase grating created with arbitrarily weak fields was proposed to allow almost 30% of a probe beam to be diffracted into the first diffraction order.
Abstract: Exploiting the giant Kerr nonlinearity associated with electromagnetically induced transparency, an atomic phase grating created with arbitrarily weak fields is proposed. Almost 30% of a probe beam can be diffracted into the first diffraction order.
97 citations
TL;DR: An innovative variable-focus flat liquid-crystal diffractive lens (LCDL) with 95% diffraction efficiency and millisecond switching times using a +/-2.4 V ac input is demonstrated.
Abstract: We demonstrate an innovative variable-focus flat liquid-crystal diffractive lens (LCDL) with 95% diffraction efficiency and millisecond switching times using a +/-2.4 V ac input. This lens is based on the electrical modulation of a 3 mum layer of nematic liquid-crystal sandwiched between a Fresnel zone electrode structure and a reference substrate. Each zone is divided into 12 subzones to digitize the phase profiles and define the phase wrapping points. The focusing power can rapidly be switched by electrically changing the number of subzones and re-establishing the wrapping points. Potential applications include zooms with no moving parts and autofocus lenses for compact imaging devices.
91 citations
TL;DR: In this article, a method to estimate changes in measured diffraction intensities in angular resolved EUV scatterometry induced by line roughness is presented, which can be used to include the estimation of the roughness into the structure reconstruction algorithm.
Abstract: Scatterometry is a common technique for the characterization of nanostructured surfaces. With shrinking dimensions, fewer and fewer propagating diffraction orders exist, and structure roughness becomes more important. Recent investigations suggest that roughness has to be taken into account for structure reconstruction. The short wavelength of the extreme UV (EUV) is advantageous, since it provides more propagating diffraction orders as compared to UV and visible radiation and increases the sensitivity to small structural features, particularly roughness. We present a method to numerically estimate changes in measured diffraction intensities in angular resolved EUV scatterometry induced by line roughness. The model can be used to include the estimation of the roughness into the structure reconstruction algorithm.
74 citations
TL;DR: A new glucose sensing strategy has been developed by using diffraction-gratings of a stimuli-responsive hydrogel bearing phenylboronic acid groups that showed ability for the continuous detection and were durable for repeated applications.
64 citations
TL;DR: Experimental studies of the diffraction efficiency changes during the holographic diffraction grating recording process in photochromic polymer revealed the main differences in the diffractions grating formation process for s-s, p-p, s-p and RCP-LCP polarization configurations.
Abstract: The holographic grating recording process in thin films of amorphous azobenzene-functionalized polymers has been widely reported in the literature. In spite of the many reports, little is known about the mechanisms responsible for different temporal behaviors of the diffraction efficiency during long recording times. Here, we report on experimental studies of the diffraction efficiency changes during the holographic diffraction grating recording process in photochromic polymer. The gratings were inscribed for four different polarization combinations of the recording beams: s-s, p-p, s-p and right to left circular polarization (RCP-LCP) employing the degenerate two-wave mixing technique. The grating recording process was simultaneously monitored by three different wavelengths: 514.5 nm (writing) and 632.8 and 904 nm (reading). The temporal evolution of the diffraction efficiency (for all polarization configurations and for each wavelengths) was precisely fitted within the model, which assumes simultaneous formation of the absorption grating and three coupling phase gratings shifted by 0 or π with respect to each other. Two of the phase gratings originate from the refractive index grating changes in the bulk (volume) of a material and the third one from the surface relief modulation. The model enabled us to extract relevant parameters for each grating such as the build-up time constant, its final amplitude, and the phase shifts between phase gratings. Performed studies and the discussion of results revealed the main differences in the diffraction grating formation process for s-s, p-p, s-p, and RCP-LCP polarization configurations.
62 citations
TL;DR: Nanoparticles are spatially arranged by holographical means in a photopolymer that show remarkably efficient diffraction of cold neutrons up to about 50% for effective thicknesses of only 200 μm, which opens up a profound perspective for next generation neutron-optical devices with the capability to tune or modulate the neutron diffraction efficiency.
Abstract: We report a breakthrough in the search for versatile diffractive elements for cold neutrons Nanoparticles are spatially arranged by holographical means in a photopolymer These grating structures show remarkably efficient diffraction of cold neutrons up to about 50% for effective thicknesses of only $200\text{ }\ensuremath{\mu}\mathrm{m}$ They open up a profound perspective for next generation neutron-optical devices with the capability to tune or modulate the neutron diffraction efficiency
62 citations
TL;DR: Results show that damage threshold is governed by the value of the maximum electric field intensity inside the grating pillar, and thresholds close to 3 J/cm2 beam normal are obtained with this new MMLD grating being thus an interesting alternative to gold and pure dielectric gratings for pulse compression applications.
Abstract: We report on manufacturing and testing results of high efficiency mixed metal dielectric gratings (MMLD) for high power pulse compression applications. The gratings with 1780 l/mm are etched in the top low index layer of a Au-(SiO2/HfO2)4-SiO2 mirror stack. Various grating profiles manufactured in order to modify the near electric field distribution are damage tested on a facility operating at 1.053 µm, 500 fs pulse duration. We evidence that damage threshold is governed by the value of the maximum electric field intensity inside the grating pillar. Moreover thresholds close to 3 J/cm2 beam normal are obtained with this new MMLD grating being thus an interesting alternative to gold and pure dielectric gratings for pulse compression applications.
61 citations
TL;DR: In this paper, a theoretical model for the formation of a short-exposure holographic grating is presented, which accounts for both monomer and polymer diffusion and distinguishes between short polymer chains capable of diffusing and long polymer chains that are immobile.
Abstract: A theoretical model for formation of a short-exposure holographic grating is presented. The model accounts for both monomer and polymer diffusion and distinguishes between short polymer chains capable of diffusing and long polymer chains that are immobile. It is shown that the experimentally observed decrease of diffraction efficiency at higher spatial frequency can be predicted by assuming diffusion of short-chain polymers away from the bright fringes. The time evolution of the refractive-index modulation after a short exposure is calculated and compared with experimental results. The effects of diffusion coefficients, polymerization rates, intensity, and spatial frequency of recording on the properties of weak diffraction gratings are investigated by numerical simulations.
60 citations
TL;DR: In this paper, a phase modulation of the surface plasmon provided by the dielectric block with varying geometric parameters located on the interface is proposed, based on a rigorous coupled wave analysis.
Abstract: We present a method of designing diffractive optical elements for transforming and focusing surface plasmons. The method is based on a phase modulation of the surface plasmon provided by the dielectric block with varying geometric parameters located on the interface. The problem of SP diffraction by a dielectric block is solved using the rigorous coupled wave analysis. We demonstrate that the modulation can be implemented not only by changing the length of the dielectric block at fixed height, but also by changing the height at fixed length as well as by simultaneous changing of both parameters. The height modulation and combined height–length modulation are believed to be considered for the first time. As an example, the design of diffractive elements for focusing surface plasmons is considered. It is demonstrated that combining the height and length modulations allows us to increase the diffraction efficiency by more than 10%.
58 citations
TL;DR: X-ray powder diffraction with a femtosecond time resolution is introduced to map ultrafast structural dynamics of polycrystalline condensed matter and how to derive transient charge density maps of the material from the extensive set of diffraction data in a quantitative way is described.
Abstract: X-ray powder diffraction with a femtosecond time resolution is introduced to map ultrafast structural dynamics of polycrystalline condensed matter. Our pump-probe approach is based on photoexcitation of a powder sample with a femtosecond optical pulse and probing changes of its structure by diffracting a hard X-ray pulse generated in a laser-driven plasma source. We discuss the key aspects of this scheme including an analysis of detection sensitivity and angular resolution. Applying this technique to the prototype molecular material ammonium sulfate, up to 20 powder diffraction rings are recorded simultaneously with a time resolution of 100 fs. We describe how to derive transient charge density maps of the material from the extensive set of diffraction data in a quantitative way.
TL;DR: Three-wave nonlinear interactions in chirped quasi-phase-matched (QPM) gratings are shown to exhibit conversion efficiency approaching 100% with increasing input pump and signal intensities, evading backconversion.
Abstract: Three-wave nonlinear interactions in chirped quasi-phase-matched (QPM) gratings are shown to exhibit conversion efficiency approaching 100% with increasing input pump and signal intensities, evading backconversion, as long as the idler vanishes at the input and the QPM grating is sufficiently chirped. The signal phase is described in terms of Kerr-like self- and cross-phase modulations, in the cascade χ((3)) approximation. Achieving high gain and efficiency simultaneously can lead to a large nonlinear phase, and the resulting trade-off is discussed.
TL;DR: The code developed and tested is found to be accurate and efficient for solving off-plane diffraction problems including high-conductive gratings, surfaces with edges, real profiles, and gratings working at short wavelengths.
Abstract: Off-plane scattering of time-harmonic plane waves by a plane diffraction grating with arbitrary conductivity and general surface profile is considered in a rigorous electromagnetic formulation. Integral equations for conical diffraction are obtained involving, besides the boundary integrals of the single and double layer potentials, singular integrals, the tangential derivative of single-layer potentials. We derive an explicit formula for the calculation of the absorption in conical diffraction. Some rules that are expedient for the numerical implementation of the theory are presented. The efficiencies and polarization angles compared with those obtained by Lifeng Li for transmission and reflection gratings are in a good agreement. The code developed and tested is found to be accurate and efficient for solving off-plane diffraction problems including high-conductive gratings, surfaces with edges, real profiles, and gratings working at short wavelengths.
TL;DR: The enhancement in multiplexing is presented as a simple and efficient method to improve response of the material and homogeneity of diffraction efficiency and provides a significant foundation for the application of dark enhancement in holographic storage.
Abstract: The dark enhancements of diffraction efficiency in single and multiple gratings are investigated theoretically and experimentally in phenanthrenequinone doped poly-(methyl methacrylate) materials. It is demonstrated a possibility to improve holographic characteristics of the material via the enhancement. Nearly 17-fold increment of diffraction efficiency is observed after exposure. The dependences of PQ’s concentration on the rate and increment of dark enhancement are achieved quantitatively. And the enhancement in multiplexing is presented as a simple and efficient method to improve response of the material and homogeneity of diffraction efficiency. PQ’s diffusion and enhancement process of refractive index modulation are simulated by a diffusion model for describing enhancement dynamics qualitatively and quantitatively. This study provides a significant foundation for the application of dark enhancement in holographic storage.
TL;DR: It is demonstrated that more than 65 percent of the incident-wave energy can be transmitted unidirectionally with less than 0.22 percent transmission in the opposite direction at normal incidence for TE polarization.
Abstract: We achieve a broadband unidirectional transmission or One-way diffraction grating by cascading two parallel gratings made of isotropic material with different periods. In order to significantly reduce the reciprocal transmission of the zero order, one of them is chosen to be a subwavelength grating and designed as a wideband reflector for the incident-wave. It is demonstrated that more than 65 percent of the incident-wave energy can be transmitted unidirectionally with less than 0.22 percent transmission in the opposite direction at normal incidence for TE polarization. And, the relative bandwidth of the unidirectional transmission is greater than 10 percent.
TL;DR: Measurements are reported that show, for a 5000l/mm grating diffracting in the third order, a diffraction efficiency of 37.6% at a wavelength of 13.6nm.
Abstract: Volume x-ray gratings consisting of a multilayer coating deposited on a blazed substrate can diffract with very high efficiency, even in high orders if diffraction conditions in-plane (grating) and out-of-plane (Bragg multilayer) are met simultaneously. This remarkable property, however, depends critically on the ability to create a structure with near atomic perfection. In this Letter we report on a method to produce these structures. We report measurements that show, for a 5000l/mm grating diffracting in the third order, a diffraction efficiency of 37.6% at a wavelength of 13.6nm. This work now shows a direct route to achieving high diffraction efficiency in high order at wavelengths throughout the soft x-ray energy range.
TL;DR: The design, fabrication, and experimental demonstration of a circular Dammann grating element generating a point-spread function of two concentric rings with equal intensity is described.
Abstract: We describe the design, fabrication, and experimental demonstration of a circular Dammann grating element generating a point-spread function of two concentric rings with equal intensity. The element was fabricated using grayscale lithography, providing a smooth and accurate phase profile. As a result, we obtained high diffraction efficiency and good uniformity between the two rings.
TL;DR: More than 97% flat-top diffraction efficiency in the -1st-order TE polarization over a 110 nm wavelength range around 800 nm in an all-dielectric grating is designed by a simulated annealing algorithm and the Fourier mode method, providing a way for high-efficiency chirped-pulse amplification to be used in an ultrashort high-power pulse laser system based on all- dielectric gratings.
Abstract: More than 97% flat-top diffraction efficiency in the -1st-order TE polarization over a 110 nm wavelength range around 800 nm in an all-dielectric grating is designed by a simulated annealing algorithm and the Fourier mode method. Its band is near to the maximum bandwidth provided by a dielectric high-reflectivity mirror under the match layer. This result will provide a way for high-efficiency chirped-pulse amplification to be used in an ultrashort high-power pulse laser system based on all-dielectric gratings. Furthermore, an effective method for broadband high-efficiency all-dielectric grating design is presented in this Letter.
TL;DR: This work demonstrates a design approach for binary multi-phase level computer generated holograms based on the effective medium approach that leads to a significant cost reduction by simplifying the fabrication process.
Abstract: The ability of subwavelength structures to create an artificial effective index opens up new perspectives in designing highly efficient diffractive optical elements. We demonstrate a design approach for binary multi-phase level computer generated holograms based on the effective medium approach. The phase pattern is formed by various subwavelength structures that cause a certain phase delay to an incident light wave. This binary structure approach leads to a significant cost reduction by simplifying the fabrication process. For demonstration, a three-phase level element, operating in the visible range, is fabricated and experimentally evaluated.
TL;DR: Parallel femtosecond refractive index laser inscription of clinical grade poly(methyl methacrylate) (PMMA) at 775 nm, 170 fs pulselength is demonstrated with multiple low fluence beams generated with the aid of a spatial light modulator.
Abstract: Parallel femtosecond refractive index laser inscription of clinical grade poly(methyl methacrylate) (PMMA) at 775 nm, 170 fs pulselength is demonstrated with multiple low fluence beams generated with the aid of a spatial light modulator. Using optimised computer-generated holograms (CGHs), 16 diffracted near identical beams were focused simultaneously within bulk PMMA to create a series of 19 μm pitch, 5 mm×5 mm×1–4 mm thick volume phase gratings at high speed. First order diffraction efficiency rises with grating thickness in accord with diffraction theory, reaching 75% at the first Bragg angle (4 mm thick) with fabrication time around 1 hour. By carefully stitching filamentary modifications while eliminating effects such as pulse front tilt during inscription, gratings exhibit high uniformity, which has not been achieved previously using femtosecond inscription. Highly uniform modification is exhibited throughout the material consistent with the observed excellent angular selectivity and low background scatter and quantitative comparison with first order diffraction theory is satisfactory. The diffraction efficiency and hence refractive index profile shows a temporal behaviour related to the material response after exposure. Simultaneous 3D modification at different depths is also demonstrated, highlighting the potential of creating complex 3D integrated optical circuits at high speed through the application of CGHs.
TL;DR: In this article, the authors characterize the resistance of diffractive waveplates to optical radiation, the effects of temperature and deformations, and the boundary effects in the manufacturing process make it necessary to use substrates larger than the desired aperture of the DW.
Abstract: The development history of polarization gratings (PGs), with origins in holography and Bragg gratings, accentuated and
reinforced their perception as gratings. We highlight their nature as waveplates - diffractive waveplates (DWs) - and
stress their family connection to vector vortex waveplates. This approach provides a straightforward understanding of
the unusual properties of PGs, such as nearly 100% diffraction in thin material layers, the presence of only one
diffraction order for a circularly polarized beam, wide diffraction bandwidth and the possibility of achromatic behavior.
With technology being ripe for applications such as beam steering, and optical switching, we characterize the resistance
of DWs to optical radiation, the effects of temperature and deformations. We also show that the boundary effects in the
manufacturing process make it necessary to use substrates larger than the desired aperture of the DW. The multicomponent
systems are discussed for developing normally transmissive switchable imaging systems, beam scanning, and
achromatic diffraction.
TL;DR: In this article, the semi-intercalation of an azo-dye Disperse Red 1 (DR1) into a biopolymeric material made of deoxyribonucleic acid (DNA) complexed with the cationic surfactant hexadecyltrimethyl-ammonium chloride (CTMA) was used to model the unique photochromic properties of the DR1:DNA-CTMA system.
TL;DR: What the authors believe to be a new method for designing multilayer diffractive optical elements for wideband with consideration of polychromatic integral diffraction efficiency (PIDE) is presented and the maximum PIDE over the entire waveband for MLDOEs can be obtained.
Abstract: What we believe to be a new method for designing multilayer diffractive optical elements (MLDOEs) for wideband with consideration of polychromatic integral diffraction efficiency (PIDE) is presented. The benefit of this method is that the maximum PIDE over the entire waveband for MLDOEs can be obtained. The design process and simulation of the MLDOEs with regard to an example for visible waveband are described, and the comparison of diffraction efficiencies of the MLDOEs for different choices of design wavelengths with different methods is given.
TL;DR: Simulation and experimental results for the aperiodic and multiplexed imaging gratings formed in PQ-PMMA at 488nm and probed with a spherical wave at 633nm show proof of consistency and usefulness of the proposed models.
Abstract: A new methodology describing the effects of aperiodic and multiplexed gratings in volume holographic imaging systems (VHIS) is presented. The aperiodic gratings are treated as an ensemble of localized planar gratings using coupled wave methods in conjunction with sequential and non-sequential ray-tracing techniques to accurately predict volumetric diffraction effects in VHIS. Our approach can be applied to aperiodic, multiplexed gratings and used to theoretically predict the performance of multiplexed volume holographic gratings within a volume hologram for VHIS. We present simulation and experimental results for the aperiodic and multiplexed imaging gratings formed in PQ-PMMA at 488nm and probed with a spherical wave at 633nm. Simulation results based on our approach that can be easily implemented in ray-tracing packages such as Zemax® are confirmed with experiments and show proof of consistency and usefulness of the proposed models.
TL;DR: In this article, the spatial anisotropy of the acousto-optic (AO) figure of merit M2 in LiNbO3 crystals is analyzed based on the indicative surfaces calculated for several geometries of the AO diffraction.
Abstract: We report the spatial anisotropy of the acousto-optic (AO) figure of merit M2 in LiNbO3 crystals. The analysis is based on the indicative surfaces being calculated for several geometries of the AO diffraction. Basing on these results the most efficient geometries of AO cells made of LiNbO3 crystals are determined. It is revealed that the cells made of certain nondirect crystal cuts provide several times better AO diffraction efficiency comparing to the traditional ones, i.e., made of direct cuts of LiNbO3. The obtained results present considerable practical interest since may be useful in a designing of highly efficient AO cells made of LiNbO3 crystals. The methodology developed in the present work may be applied to other crystal materials as well.
TL;DR: A novel formulation of the finite element method adapted to the calculation of the vector field diffracted by an arbitrarily shaped crossed-grating embedded in a multilayered stack and illuminated by an arbitrary polarized plane wave under oblique incidence shows a remarkable convergence even for coarse meshes.
Abstract: We propose a novel formulation of the finite element method adapted to the calculation of the vector field diffracted by an arbitrarily shaped crossed-grating embedded in a multilayered stack and illuminated by an arbitrarily polarized plane wave under oblique incidence. A complete energy balance (transmitted and reflected diffraction efficiencies and losses) is deduced from field maps. The accuracy of the proposed formulation has been tested using classical cases computed with independent methods. Moreover, to illustrate the independence of our method with respect to the shape of the diffractive object, we present the global energy balance resulting from the diffraction of a plane wave by a lossy thin torus crossed-grating. Finally, computation time and convergence as a function of the mesh refinement are discussed. As far as integrated energy values are concerned, the presented method shows a remarkable convergence even for coarse meshes.
TL;DR: Results indicate a faster rise and fall times which is attributed to the reduction in size of the liquid crystal droplets formed and a reduction in switching voltage due to change in dielectric properties of the medium as manifested by a rise in capacitance.
Abstract: This work focuses on experimentally demonstrating the modification in diffusion kinetics, formation of holographic polymer dispersed liquid crystal gratings and an improvement in its electro optic response by doping them with multi-walled carbon nanotubes Results indicate a faster rise and fall times which is attributed to the reduction in size of the liquid crystal droplets formed and a reduction in switching voltage due to change in dielectric properties of the medium as manifested by a rise in capacitance Real time diffraction efficiency measurements reveal a time delay in the appearance of the diffracted order due to non-participation of the nanotube in the polymerization induced phase separation process An analysis of this effect is presented based on the Stoke- Einstein’s diffusion equation incorporating shape anisotropy of the nanotubes
TL;DR: A diffractive model is proposed to evaluate the modulation diffraction efficiency of phase diffractive optical elements (DOEs) in the presence of phase fluctuations and results show good agreement with the numerical calculation given by the model.
Abstract: Digital addressing of the electrical signal in spatial light modulators, as it is the case in present liquid crystal on silicon (LCoS) displays, may lead to temporal phase fluctuations in the optical beam. In diffractive optics applications a reduction in the modulation diffraction efficiency may be expected. Experimental work is done characterizing the fluctuations amplitude and phase depth for three different digital addressing sequences. We propose a diffractive model to evaluate the modulation diffraction efficiency of phase diffractive optical elements (DOEs) in the presence of phase fluctuations. Best results are obtained for the most stable electrical sequence even though its phase depth is as small as 280°. The results show good agreement with the numerical calculation given by the model.
TL;DR: In this article, a simple, compact, and automatically aligned ultrashort-pulse compressor that uses only a single diffraction element (a grating or a grism) is presented.
Abstract: We introduce and demonstrate a simple, compact, and automatically aligned ultrashort-pulse compressor that uses only a single diffraction element—a grating or a grism (a grating on a prism). This design automatically has unity beam magnification and automatically contributes zero spatiotemporal distortions to the pulse, thus avoiding spatial chirp, angular dispersion, pulse-front tilt, and all other first-order spatiotemporal distortions. It is comprised of only three elements: a diffraction element, a corner cube, and a roof mirror. Half the size of comparable two-grating compressors, it can provide large amounts of negative group-delay dispersion with small translations of the corner cube. The device can operate on pulses with both large and small bandwidths by varying the corner-cube position. Using a grism as the diffraction element, material dispersion up to the third order can be compensated, and we demonstrated compensation for 10 m of optical fiber for 800 nm pulses.
TL;DR: In this paper, the mathematical theory of laser beam splitting gratings is discussed for both continuous and Dammann gratings, and the theory of one and two dimensional gratings are discussed.
Abstract: We review the mathematical theory of laser beam splitting gratings. We discuss the theory of one and two dimensional gratings, for both continuous and Dammann gratings.