Showing papers on "Physical optics published in 2013"
TL;DR: An optical model for light field microscopy based on wave optics, instead of previously reported ray optics models is presented, and a 3-D deconvolution method is presented that is able to reconstruct volumes at higher spatial resolution, and with better optical sectioning, than previously reported.
Abstract: Light field microscopy is a new technique for high-speed volumetric imaging of weakly scattering or fluorescent specimens It employs an array of microlenses to trade off spatial resolution against angular resolution, thereby allowing a 4-D light field to be captured using a single photographic exposure without the need for scanning The recorded light field can then be used to computationally reconstruct a full volume In this paper, we present an optical model for light field microscopy based on wave optics, instead of previously reported ray optics models We also present a 3-D deconvolution method for light field microscopy that is able to reconstruct volumes at higher spatial resolution, and with better optical sectioning, than previously reported To accomplish this, we take advantage of the dense spatio-angular sampling provided by a microlens array at axial positions away from the native object plane This dense sampling permits us to decode aliasing present in the light field to reconstruct high-frequency information We formulate our method as an inverse problem for reconstructing the 3-D volume, which we solve using a GPU-accelerated iterative algorithm Theoretical limits on the depth-dependent lateral resolution of the reconstructed volumes are derived We show that these limits are in good agreement with experimental results on a standard USAF 1951 resolution target Finally, we present 3-D reconstructions of pollen grains that demonstrate the improvements in fidelity made possible by our method
472 citations
Book•
01 Dec 2013
TL;DR: In this article, the authors present a list of symbols for high-resolution images of Crystals and their defects, including Stem and Z-Contrast, Wave Optics, and Coherence and Fourier Optics.
Abstract: Preface Acknowledgements List of Symbols 1. Preliminaries 2. Electron Optics 3. Wave Optics 4. Coherence and Fourier Optics 5. High-Resolution Images of Crystals and their Defects 6. HREM in Biology, Organic Crystals and Radiation Damage 7. Image Processing and Superresolution Schemes 8. Stem and Z-Contrast 9. Electron Sources and Detectors 10. Measurement of Electron-optical Parameters Affecting High-Resolution Images 11. Instabilities and the Microscope Environment 12. Experimental Methods 13. Associated Techniques Appendix 1 Appendix 2 Appendix 3 Appendix 4 Appendix 5
365 citations
TL;DR: In this article, the authors give an overview of recent advances on the effect from classical optics to nonlinear optics and quantum optics, and present the physical aspects of the self-imaging phenomenon.
Abstract: The Talbot effect, also referred to as self-imaging or lensless imaging, is of the phenomena manifested by a periodic repetition of planar field distributions in certain types of wave fields. This phenomenon is finding applications not only in optics, but also in a variety of research fields, such as acoustics, electron microscopy, plasmonics, x ray, and Bose–Einstein condensates. In optics, self-imaging is being explored particularly in image processing, in the production of spatial-frequency filters, and in optical metrology. In this article, we give an overview of recent advances on the effect from classical optics to nonlinear optics and quantum optics. Throughout this review article there is an effort to clearly present the physical aspects of the self-imaging phenomenon. Mathematical formulations are reduced to the indispensable ones. Readers who prefer strict mathematical treatments should resort to the extensive list of references. Despite the rapid progress on the subject, new ideas and applications of Talbot self-imaging are still expected in the future.
310 citations
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TL;DR: An overview of the current state of the field and an outlook to future prospects is given in this paper, where the authors also present a survey of the state-of-the-art in the field of quantum optics with X-rays.
Abstract: Quantum optics with X-rays has long been a somewhat exotic activity, but it is now rapidly becoming relevant as precision x-ray optics and novel X-ray light sources, and high-intensity lasers are becoming available. This article gives an overview of the current state of the field and an outlook to future prospects.
120 citations
TL;DR: In this paper, a new experiment demonstrates that two breathers, when their initial shapes and propagations are properly controlled, can collide to make a new giant ''rogue'' wave.
Abstract: Recently nonlinear fiber optics has revealed the existence of ``breathers,'' a new form of solitons with periodic oscillations on a finite background. But, how do such breathers, when they appear at the same time, interact with each other? A new experiment demonstrates that two such breathers, when their initial shapes and propagations are properly controlled, can collide to make a new giant ``rogue'' wave.
113 citations
TL;DR: A tissue optics plug-in that interfaces with the GEANT4/GAMOS Monte Carlo (MC) architecture is described, providing a means of simulating radiation-induced light transport in biological media for the first time and showing excellent agreement with currently employed biomedical optics MC codes.
Abstract: We describe a tissue optics plug-in that interfaces with the GEANT4/GAMOS Monte Carlo (MC) architecture, providing a means of simulating radiation-induced light transport in biological media for the first time. Specifically, we focus on the simulation of light transport due to the Cerenkov effect (light emission from charged particle’s traveling faster than the local speed of light in a given medium), a phenomenon which requires accurate modeling of both the high energy particle and subsequent optical photon transport, a dynamic coupled process that is not well-described by any current MC framework. The results of validation simulations show excellent agreement with currently employed biomedical optics MC codes, [i.e., Monte Carlo for Multi-Layered media (MCML), Mesh-based Monte Carlo (MMC), and diffusion theory], and examples relevant to recent studies into detection of Cerenkov light from an external radiation beam or radionuclide are presented. While the work presented within this paper focuses on radiation-induced light transport, the core features and robust flexibility of the plug-in modified package make it also extensible to more conventional biomedical optics simulations. The plug-in, user guide, example files, as well as the necessary files to reproduce the validation simulations described within this paper are available online at http://www.dartmouth.edu/optmed/research-projects/monte-carlo-software.
71 citations
11 May 2013-Nuclear Instruments & Methods in Physics Research Section A-accelerators Spectrometers Detectors and Associated Equipment
TL;DR: In this paper, the first measurements of the focal spot in the DiProI beamline end-station were reported and compared with the predictions computed with Shadow code and WISE code, starting from the mirror surface profile characterization.
Abstract: FERMI@Elettra, the first seeded EUV-SXR free electron laser (FEL) facility located at Elettra Sincrotrone Trieste has been conceived to provide very short (10–100 fs) pulses with ultrahigh peak brightness and wavelengths from 100 nm to 4 nm. A section fully dedicated to the photon transport and analysis diagnostics, named PADReS, has already been installed and commissioned. Three of the beamlines, EIS-TIMEX, DiProI and LDM, installed after the PADReS section, are in advanced commissioning state and will accept the first users in December 2012. These beam lines employ active X-ray optics in order to focus the FEL beam as well as to perform a controlled beam-shaping at focus.
Starting from mirror surface metrology characterization, it is difficult to predict the focal spot shape applying only methods based on geometrical optics such as the ray tracing. Within the geometrical optics approach one cannot take into account the diffraction effect from the optics edges, i.e. the aperture diffraction, and the impact of different surface spatial wavelengths to the spot size degradation. Both these effects are strongly dependent on the photon beam energy and mirror incident angles.
We employed a method based on physical optics, which applies the Huygens–Fresnel principle to reflection (on which the WISE code is based). In this work we report the results of the first measurements of the focal spot in the DiProI beamline end-station and compare them to the predictions computed with Shadow code and WISE code, starting from the mirror surface profile characterization.
60 citations
TL;DR: The diffraction effect is considered, the intensity distribution of light with multiple micro-lenses is analyzed, and a DOF calculation formula is derived for integral imaging display system based on wave optics.
Abstract: In this paper, we analyze the depth of field (DOF) of integral imaging displays based on wave optics. With considering the diffraction effect, we analyze the intensity distribution of light with multiple micro-lenses and derive a DOF calculation formula for integral imaging display system. We study the variations of DOF values with different system parameters. Experimental results are provided to verify the accuracy of the theoretical analysis. The analyses and experimental results presented in this paper could be beneficial for better understanding and designing of integral imaging displays.
59 citations
TL;DR: A difference between the filter characteristics derived in each case is found and the equivalence of the two approaches when applied to a weakly scattering object is explained.
Abstract: The characterization of imaging methods as three-dimensional (3D) linear filtering operations provides a useful way to compare the 3D performance of optical surface topography measuring instruments, such as coherence scanning interferometry, confocal and structured light microscopy. In this way, the imaging system is defined in terms of the point spread function in the space domain or equivalently by the transfer function in the spatial frequency domain. The derivation of these characteristics usually involves making the Born approximation, which is strictly only applicable to weakly scattering objects; however, for the case of surface scattering, the system is linear if multiple scattering is assumed to be negligible and the Kirchhoff approximation is assumed. A difference between the filter characteristics derived in each case is found. However this paper discusses these differences and explains the equivalence of the two approaches when applied to a weakly scattering object.
56 citations
21 Jul 2013
TL;DR: This paper proposes and demonstrates a practical method, which takes into account the limitations of existing micro-fabrication techniques such as photolithography to design and fabricate a range of reflection effects, based on wave interference, albeit with a lower angular resolution.
Abstract: Recent attempts to fabricate surfaces with custom reflectance functions boast impressive angular resolution, yet their spatial resolution is limited. In this paper we present a method to construct spatially varying reflectance at a high resolution of up to 220dpi, orders of magnitude greater than previous attempts, albeit with a lower angular resolution. The resolution of previous approaches is limited by the machining, but more fundamentally, by the geometric optics model on which they are built. Beyond a certain scale geometric optics models break down and wave effects must be taken into account. We present an analysis of incoherent reflectance based on wave optics and gain important insights into reflectance design. We further suggest and demonstrate a practical method, which takes into account the limitations of existing micro-fabrication techniques such as photolithography to design and fabricate a range of reflection effects, based on wave interference.
50 citations
01 Jul 2013
TL;DR: In this paper, the authors present a method to construct spatially varying reflectance at a high resolution of up to 220dpi, orders of magnitude greater than previous attempts, albeit with a lower angular resolution.
Abstract: Recent attempts to fabricate surfaces with custom reflectance functions boast impressive angular resolution, yet their spatial resolution is limited In this paper we present a method to construct spatially varying reflectance at a high resolution of up to 220dpi, orders of magnitude greater than previous attempts, albeit with a lower angular resolution The resolution of previous approaches is limited by the machining, but more fundamentally, by the geometric optics model on which they are built Beyond a certain scale geometric optics models break down and wave effects must be taken into account We present an analysis of incoherent reflectance based on wave optics and gain important insights into reflectance design We further suggest and demonstrate a practical method, which takes into account the limitations of existing micro-fabrication techniques such as photolithography to design and fabricate a range of reflection effects, based on wave interference
TL;DR: A Fourier formulation of coded-aperture x-ray phase-contrast imaging is derived, based on the wave theory of optics in the Fresnel approximation, to develop a flexible, efficient, and general simulation algorithm that can be easily adapted to other implementations of x-rays phase contrast imaging.
Abstract: We derive a Fourier formulation of coded-aperture x-ray phase-contrast imaging, based on the wave theory of optics in the Fresnel approximation. We use this model to develop a flexible, efficient, and general simulation algorithm that can be easily adapted to other implementations of x-ray phase contrast imaging. Likewise, the algorithm enables a simple extension to 2D aperture designs, different acquisition schemes, etc. Problems related to numerical implementation of the algorithm are analyzed in detail, and simple rules are derived that enable us to avoid or at least mitigate them. Finally, comparisons with experimental data and data obtained with a different simulation algorithm are presented to validate the model and demonstrate its advantages in practical implementations. This also enabled us to demonstrate an increase in computational speed of more than one order of magnitude over a previous algorithm.
TL;DR: The results show a more than 307% improvement in the total LEE enhancement of the NPSS LED with the optimal solution compared to the conventional LED.
Abstract: In this paper, we propose a method to analyze the light extraction efficiency (LEE) enhancement of a nanopatterned sapphire substrates (NPSS) light-emitting diode (LED) by comparing wave optics software with ray optics software Finite-difference time-domain (FDTD) simulations represent the wave optics software and Light Tools (LTs) simulations represent the ray optics software First, we find the trends of and an optimal solution for the LEE enhancement when the 2D-FDTD simulations are used to save on simulation time and computational memory The rigorous coupled-wave analysis method is utilized to explain the trend we get from the 2D-FDTD algorithm The optimal solution is then applied in 3D-FDTD and LTs simulations The results are similar and the difference in LEE enhancement between the two simulations does not exceed 85% in the small LED chip area More than 104 times computational memory is saved during the LTs simulation in comparison to the 3D-FDTD simulation Moreover, LEE enhancement from the side of the LED can be obtained in the LTs simulation An actual-size NPSS LED is simulated using the LTs The results show a more than 307% improvement in the total LEE enhancement of the NPSS LED with the optimal solution compared to the conventional LED
11 May 2013-Nuclear Instruments & Methods in Physics Research Section A-accelerators Spectrometers Detectors and Associated Equipment
TL;DR: In this article, a deformation of the mirror can be made to endow the focus with a desired size and distribution, via piezo actuators as done at the EIS-TIMEX beamline of FERMI@Elettra.
Abstract: X-ray mirrors with high focusing performances are in use in both mirror modules for X-ray telescopes and in synchrotron and FEL (Free Electron Laser) beamlines. A degradation of the focus sharpness arises in general from geometrical deformations and surface roughness, the former usually described by geometrical optics and the latter by physical optics. In general, technological developments are aimed at a very tight focusing, which requires the mirror profile to comply with the nominal shape as much as possible and to keep the roughness at a negligible level. However, a deliberate deformation of the mirror can be made to endow the focus with a desired size and distribution, via piezo actuators as done at the EIS-TIMEX beamline of FERMI@Elettra. The resulting profile can be characterized with a Long Trace Profilometer and correlated with the expected optical quality via a wavefront propagation code. However, if the roughness contribution can be neglected, the computation can be performed via a ray-tracing routine, and, under opportune assumptions, the focal spot profile (the Point Spread Function, PSF) can even be predicted analytically. The advantage of this approach is that the analytical relation can be reversed; i.e., from the desired PSF the required mirror profile can be computed easily, thereby avoiding the use of complex and time-consuming numerical codes. The method can also be suited in the case of spatially inhomogeneous beam intensities, as commonly experienced at synchrotrons and FELs. In this work we expose the analytical method and the application to the beam shaping problem.
TL;DR: In this article, a study of the correlation between the power signals received at both ends of bidirectional free-space optical links is presented, and an ideal (theoretically 100%) power-signal correlation can be achieved in optical links with specially designed monostatic transceivers based on single-mode fiber collimators.
Abstract: A study of the correlation between the power signals received at both ends of bidirectional free-space optical links is presented. By use of the quasi-optical approximation, we show that an ideal (theoretically 100%) power-signal correlation can be achieved in optical links with specially designed monostatic transceivers based on single-mode fiber collimators. The theoretical prediction of enhanced correlation is supported both by experiments conducted over a 7 km atmospheric path and wave optics numerical analysis of the corresponding bidirectional optical link. In the numerical simulations, we also compare correlation properties of received power signals for different atmospheric conditions and for optical links with monostatic and bistatic geometries based on single-mode fiber collimator and on power-in-the-bucket transceiver types. Applications of the observed phenomena for signal fading mitigation and turbulence-enhanced communication link security in free-space laser communication links are discussed.
TL;DR: The resonant optical tunneling effect (ROTE) is a special phenomenon that bridges the wave optics and the quantum physics, and has attracted continuous research efforts for many years as discussed by the authors.
Abstract: A resonant optical tunneling effect (ROTE) is a special phenomenon that bridges the wave optics and the quantum physics, and has attracted continuous research efforts for many years. This paper aims to summarize the latest progress of the ROTE in theoretical modeling and application studies. As the background, the analogies of photon tunneling and electron tunneling are first discussed using different optical structures and their corresponding quantum configurations. Then, two theoretical models are presented based on the optics interpretation and the quantum interpretation, respectively. Next, the applications of the ROTE are explored for optical switches and refractive index sensors. Finally, brief discussions are presented to distinguish the ROTE from some other similar phenomena.
Book•
22 Jul 2013
TL;DR: In this paper, the authors used the method of moments (MoM) to compute the field scattered by scatterers such as canonical objects (cylinder or plate) or a randomly rough surface, and also by an object above or below a random rough surface.
Abstract: In this book, the method of moments (MoM) is addressed to compute the field scattered by scatterers such as canonical objects (cylinder or plate) or a randomly rough surface, and also by an object above or below a random rough surface. Because the problem is considered two-dimensional (2D), the integral equations (IEs) are scalar and only the transverse electric (TE) and transverse magnetic (TM) polarizations are considered (no cross polarizations occur). Chapter 1 analyzes how the MoM with the point matching method and pulse basic functions is applied to convert the IEs into a linear system. In addition, chapter 1 presents the statistical parameters necessary to generate Gaussian random rough surfaces. Chapter 2 compares the MoM with the exact solution of the field scattered by a circular cylinder in free space, and with the physical optics (PO) approximation for the scattering from a plate in free space. Chapter 3 presents numerical results, obtained from the MoM combined with the efficient E-PILE method, of the scattering from two illuminated scatterers and how the E-PILE algorithm can be hybridized with asymptotic or rigorous methods valid for the scattering from a single scatterer(alone). Chapter 4 presents the same results as in Chapter 3 but for an object above a random rough surface or for a coated (circular or elliptical) cylinder. In the last two chapters, the coupling between the two scatterers is also studied in detail by inverting the impedance matrix by blocks.
TL;DR: In this article, an exact solution to the Helmholtz equation as well as its paraxial counterpart were used to perform numerical simulations of electron acceleration with a high-power TM01 beam.
Abstract: In the study of laser-driven electron acceleration, it has become customary to work within the framework of paraxial wave optics. Using an exact solution to the Helmholtz equation as well as its paraxial counterpart, we perform numerical simulations of electron acceleration with a high-power TM01 beam. For beam waist sizes at which the paraxial approximation was previously recognized valid, we highlight significant differences in the angular divergence and energy distribution of the electron bunches produced by the exact and the paraxial solutions. Our results demonstrate that extra care has to be taken when working under the paraxial approximation in the context of electron acceleration with radially polarized laser beams.
TL;DR: In this paper, it is shown that violations of the geometrical optics (GO), introduced in this technique, result in the MTPO solutions which do not satisfy the Helmholtz equation.
Abstract: Basic features of the modified theory of physical optics (MTPO) are discussed on the example of scattering at perfectly reflecting half-planes and wedges. It is shown that violations of the geometrical optics (GO), introduced in this technique, result in the MTPO solutions which do not satisfy the Helmholtz equation. They are incorrect at a finite distance from a scattering object; however it can be considered as sort of approximations for the field at a large distance from an edge and away from the GO boundaries.
TL;DR: In this paper, a physical optics based approach to synthesize shaped subreflectors to compensate the reflector distortions is presented, which is not based in computationally intensive calculation nor optimization and thus presents very low calculation times when applied to large antennas.
Abstract: Thermal and gravitational effects distort the surface of large reflector antennas and degrade the antenna pattern. When operating with electrically large reflector antennas the surface error limits the high frequency applicability. The behavior of the distorted reflector can be improved by using various techniques to compensate the reflector distortions. This communication presents a new physical optics based approach to synthesize shaped subreflectors to achieve such a compensation. The main contribution of the communication is that the method is not based in computationally intensive calculation nor optimization and thus presents very low calculation times when applied to large antennas. Representative results and comparison with previous approaches to the same problem are presented.
TL;DR: In this article, a positive answer to the question of whether the two effects are common in nature and study both effects in the more general context of optical beam shifts was given, and they found that both effects are caused by the same principle, but have been defined differently.
Abstract: The law of reflection and Snell's law are among the tenets of geometrical optics. Corrections to these laws in wave optics are respectively known as the angular Goos–Hanchen shift and Fresnel filtering. In this paper we give a positive answer to the question of whether the two effects are common in nature and we study both effects in the more general context of optical beam shifts. We find that both effects are caused by the same principle, but have been defined differently. We identify and discuss the similarities and differences that arise from the different definitions.
TL;DR: For the first time, an interferometric velocity measurement technique with embedded adaptive optics is presented for flow velocity measurements through a fluctuating air-water interface and paves the way for several kinds of optical flow measurements in various complex environments.
Abstract: Optical transmission through fluctuating interfaces of mediums with different refractive indexes is limited by the occurring distortions. Temporal fluctuations of such distortions deteriorate optical measurements. In order to overcome this shortcoming we propose the use of adaptive optics. For the first time, an interferometric velocity measurement technique with embedded adaptive optics is presented for flow velocity measurements through a fluctuating air-water interface. A low order distortion correction technique using a fast deformable mirror and a Hartmann-Shack camera with high frame rate is employed. The obtained high control bandwidth enables precise measurements also at fast fluctuating media interfaces. This methodology paves the way for several kinds of optical flow measurements in various complex environments.
TL;DR: An adaptive integration algorithm is presented for the computation of the Physical Optics (PO) electric and magnetic field scattered by electrically large objects modeled by Non-Uniform Rational B-Splines (NURBS).
Abstract: An adaptive integration algorithm is presented for the computation of the Physical Optics (PO) electric and magnetic field scattered by electrically large objects modeled by Non-Uniform Rational B-Splines (NURBS). The algorithm is the customization of a more general-purpose result that has been recently published. By using a unique formulation both impenetrable (e.g., impedance surfaces, coated conductors) as well as transparent thin sheet materials (e.g., thin dielectric panels, or frequency selective surfaces) are treated, via their Fresnel reflection and transmission coefficients. The PO radiation integral is evaluated over the NURBS parametric domain. Since most of the computer-aided geometric design (CAGD) tools are based on NURBS, the proposed algorithm allows a straightforward electromagnetic analysis of the structures by exploiting the standard available geometrical description, with no need of generating new geometrical models. Furthermore, the proposed adaptive sampling requires a number of integration points that is found to be drastically smaller than that resulting from standard Nyquist-based sampling integration algorithms. Such reduction of the sampling points is achieved by resorting to high-frequency technique concepts and allows a significant reduction of the CPU computational burden. Therefore the algorithm is efficient and particulary suitable for the electromagnetic characterization of real-life electrically large objects.
TL;DR: In this paper, a mode conversion method that enables transformation of the propagating mode from fundamental to higher-order modes by utilizing asymmetric graded index (A-GRIN) structures was proposed.
Abstract: We propose a mode conversion method that enables transformation of the propagating mode from fundamental to higher-order modes by utilizing asymmetric graded index (A-GRIN) structures. Refractive index variations of two different asymmetric gradient profiles, i.e., exponential and Luneburg lens profiles, have been approximated by two-dimensional photonic crystals (PCs). The basic structure is composed of constant radii with different lattice sizes. The designed GRIN mode converters provide relatively high transmission efficiency in the spectral region of interest and achieve the transformation in compact configuration. Numerical approaches utilizing the finite-difference time-domain and plane wave expansion methods are used to analyze the mode conversion phenomenon of proposed GRIN PC media. Analytical formulation based on ray theory is outlined to explore both ray trajectories and the physical concept of a wavefront retardation mechanism.
TL;DR: In this paper, an exact solution to the Helmholtz equation as well as its paraxial counterpart were used to perform numerical simulations of electron acceleration with a high-power TM01 beam.
Abstract: In the study of laser-driven electron acceleration, it has become customary to work within the framework of paraxial wave optics. Using an exact solution to the Helmholtz equation as well as its paraxial counterpart, we perform numerical simulations of electron acceleration with a high-power TM01 beam. For beam waist sizes at which the paraxial approximation was previously recognized valid, we highlight significant differences in the angular divergence and energy distribution of the electron bunches produced by the exact and the paraxial solutions. Our results demonstrate that extra care has to be taken when working under the paraxial approximation in the context of electron acceleration with radially polarized laser beams.
TL;DR: This paper presents a fundamental simulation method to generate synthetic aperture radar (SAR) images for moving ocean surfaces based on motion induced modulations and Bragg scattering, which are important features of ocean SAR images.
Abstract: This paper presents a fundamental simulation method to generate synthetic aperture radar (SAR) images for moving ocean surfaces. We have designed the simulation based on motion induced modulations and Bragg scattering, which are important features of ocean SAR images. The time domain simulation is able to obtain time series of microwave backscattering modulated by the orbital motions of ocean waves. Physical optics approximation is applied to calculate microwave backscattering. The computational grids are smaller than transmit microwave to demonstrate accurate interaction between electromagnetic waves and ocean surface waves. In this paper, as foundations for SAR image simulation of moving ocean surfaces, the simulation is carried out for some targets and ocean waves. The SAR images of stationary and moving targets are simulated to confirm SAR signal processing and motion induced modulation. Furthermore, the azimuth signals from the regular wave traveling to the azimuth direction also show the azimuthal shifts due to the orbital motions. In addition, incident angle dependence is simulated for irregular wind waves to compare with Bragg scattering theory. The simulation results are in good agreement with the theory. These results show that the simulation is applicable for generating numerical SAR images of moving ocean surfaces.
TL;DR: In this paper, the authors show that multi-crystal, multi-Bragg-reflection arrangements feature cumulative angular dispersion rates almost two orders of magnitude larger than those attainable with a single Bragg reflection.
Abstract: Spectrographs take snapshots of photon spectra with array detectors by dispersing photons of different energies into distinct directions and spacial locations. Spectrographs require optics with a large angular dispersion rate as the key component. In visible light optics diffraction gratings are used for this purpose. In the hard x-ray regime, achieving large dispersion rates is a challenge. Here we show that multi-crystal, multi-Bragg-reflection arrangements feature cumulative angular dispersion rates almost two orders of magnitude larger than those attainable with a single Bragg reflection. As a result, the multi-crystal arrangements become potential dispersing elements of hard x-ray spectrographs. The hard x-ray spectrograph principles are demonstrated by imaging a spectrum of photons with a record high resolution of $\Delta E \simeq 90 \mu$eV in hard x-ray regime, using multi-crystal optics as dispersing element. The spectrographs can boost research using inelastic ultra-high-resolution x-ray spectroscopies with synchrotrons and seeded XFELs.