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Digital holography for non-invasive quantitative imaging of two-dimensional materials
摘要： Digital holography has found applications in many walks of life, from medicine to metrology, due to its ability to measure complex fields. Here, we use the power of digital holography to quantitatively image two-dimensional Transition Metal Dichalcogenides (TMDs) such as MoS2 and WS2 placed on a SiO2/Si substrate and determine their complex refractive indices or layer thicknesses. By considering the different refractive indices of the TMDs as they are thinned down from bulk to monolayers and by holographically capturing both the amplitude and the phase of reflected light, single atomic layers of TMDs, about 0.7 nm thick, can be resolved. Using holography, we also predict the number of layers contained within a thick TMD flake, which shows agreement with results obtained using Atomic Force Microscopy (AFM). A Bland–Altman analysis was performed to compare our experimental results with the standard AFM measurements, yielding a limit of agreement <5 nm for samples with thicknesses ranging from 15 to 60 nm. Our technique is non-contact, non-invasive, does not require scanning, and produces a field of view of a few hundred micrometers by a few hundred micrometers in a single capture. To further our study, we also perform simulations to demonstrate how the thickness of the SiO2 layer and the laser wavelength are critical in optimizing the amplitude and phase response of a two-dimensional material. These simulations can be used as a roadmap to determine the ideal wavelength and SiO2 layer thickness that should be used to accurately determine the refractive index or thickness of any given sample.
关键词： digital holography,Atomic Force Microscopy,layer thicknesses,Bland–Altman analysis,Transition Metal Dichalcogenides,two-dimensional materials,complex refractive indices
更新于2025-09-23 15:19:57
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Dynamic quantum state holography
摘要： We present a pulse-shaper-based holographic technique for the time-resolved and phase-sensitive observation of ultrafast quantum dynamics. The technique combines bichromatic white light polarization pulse shaping with the tomographic reconstruction of photoelectron wave packets. The physical scheme is based on the interference of a probe wave packet from N + 1 resonance-enhanced multiphoton ionization via the target states and a reference wave packet from M + 1 multiphoton ionization of the ground state. To create the wave packets, we employ carrier-envelope phase stable bichromatic (Mω:Nω) pump-probe pulse sequences. The scheme is demonstrated on femtosecond Rydberg wave-packet dynamics in potassium atoms using corotating circularly polarized (2ω:3ω) pulse sequences. The interference of continuum states with different angular momenta yields a crescent-shaped photoelectron wave packet rotating in the laser polarization plane due to the interplay of the optical phase and the accumulated quantum phase. Carrier-envelope phase control of the rotation provides access to the photoelectron asymmetry, enabling background-free detection of the crescent’s angular motion which maps the bound-electron dynamics.
关键词： photoelectron wave packets,ultrafast quantum dynamics,Rydberg wave-packet dynamics,dynamic quantum state holography,bichromatic white light polarization pulse shaping
更新于2025-09-23 15:19:57
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Single-Layer Bifacial Metasurface: Full-Space Visible Light Control
摘要： Optical metasurfaces have attracted considerable attention thanks to their unprecedented ability to control the electromagnetic properties of light in subwavelength scale. These metasurface-integrated devices not only have the merit of compact form factor but also exhibit some better performance in comparison with conventional bulk optic devices. In this work, a novel metasurface that enables full-space light control is realized, offering an unconventional functionality that provides a new foothold for metasurface integration in optics. Multipolar interference and Pancharatnam–Berry phase are combined with each other and suggested as a physical background for the proposed device. As an example of the functionality, asymmetric beam steering and hologram generation are proposed and measured experimentally. As far as it is known, this is the first work achieving full-space control in visible range. Thanks to its manufactural ease and unprecedented function capability, this work will offer innovative potentials to be utilized in various integrated optic devices that need miniaturization or implementation of ingenious and light-weight optical components used in optical systems for photography, microscopy, computer vision, etc.
关键词： beam steering,metamaterials,multifunctional devices,holography,metasurfaces
更新于2025-09-19 17:15:36
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Real‐Time Three‐Dimensional Imaging of Dielectric Bodies Using Microwave/Millimeter‐Wave Holography || Microwave/Millimeter Wave Holography Based on the Concepts of Optical Holography
摘要： Holographic imaging was first introduced in the field of optics in the late forties, when Gabor aimed at improving the quality of the images in electron microscopy. He proposed an approach to capture the magnitude and phase of a wave by means of an interference pattern formed by that wave and a known reference wave. He also developed the mathematical approach to the image reconstruction from such interference patterns. Later, in the early sixties, Leith and Upatnieks improved Gabor’s experimental setup. In their method, the reference wave is a distinct beam separated from the illuminating beam by using a beam splitter. The reference beam travels at a substantial angle to the illuminating beam and is so inclined as to never illuminate the object. This new method of providing the reference wave led to separation of the overlapping images originally produced in Gabor’s experimental setup in which the reference and object waves were nearly parallel. As a result of the work of Leith and Upatnieks, higher quality images were obtained. Since then the holography method has significantly influenced optics. In general, since optical recording media such as photographic films only respond to intensity, optical holography is applied as an indirect means of capturing the phase information of the optical wave fronts. It is implemented in two steps. The first step is the hologram formation step and the second step is the wave front reconstruction step.
关键词： optical holography,microwave holography,holography,wave front reconstruction,millimeter wave holography
更新于2025-09-19 17:13:59
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Relative limitations of increasing the number of modulation levels in computer generated holography
摘要： Phase and amplitude spatial light modulators (SLMs) capable of both binary and multi-level modulation are widely available and offer a wide range of technologies to choose from for holographic applications. While the replay fields generated with multi-level phase-only SLMs are of a significantly higher quality than those generated by equivalent binary phase-only SLMs, evidence is presented in this letter that this improvement is not as marked for amplitude SLMs, where multi-level devices offer only a small benefit over their binary counterparts. Heuristic and numerical justifications for this are discussed and conclusions drawn.
关键词： Computer generated holography,Amplitude holography,Phase holography,Spatial light modulators
更新于2025-09-19 17:13:59
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[IEEE 2019 IEEE Radar Conference (RadarConf19) - Boston, MA, USA (2019.4.22-2019.4.26)] 2019 IEEE Radar Conference (RadarConf) - SISAR Imaging - Radio Holography Signal Reconstruction Based on Receiver-Transmitter Motion
摘要： Radio Holography Signal (RHS) reconstruction is the primary method used for Shadow Inverse Synthetic Aperture Radar (SISAR) imaging algorithm application. In this paper an alternative way for RHS signal reconstruction is introduced based on the motion of receiver and/or transmitter ends. In particular, a novel model for time domain RHS signal is derived assuming a moving-ends (ME) scenario followed by the RHS reconstruction method. The model and reconstruction method area assessed through simulated data.
关键词： SISAR imaging,Radio Holography Signal,moving-ends scenario,Doppler signature,Hilbert transform
更新于2025-09-19 17:13:59
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Deep Learning for Computational Mode Decomposition in Optical Fibers
摘要： Multimode ?bers are regarded as the key technology for the steady increase in data rates in optical communication. However, light propagation in multimode ?bers is complex and can lead to distortions in the transmission of information. Therefore, strategies to control the propagation of light should be developed. These strategies include the measurement of the amplitude and phase of the light ?eld after propagation through the ?ber. This is usually done with holographic approaches. In this paper, we discuss the use of a deep neural network to determine the amplitude and phase information from simple intensity-only camera images. A new type of training was developed, which is much more robust and precise than conventional training data designs. We show that the performance of the deep neural network is comparable to digital holography, but requires signi?cantly smaller efforts. The fast characterization of multimode ?bers is particularly suitable for high-performance applications like cyberphysical systems in the internet of things.
关键词： mode decomposition,deep learning,few-mode ?ber,digital holography
更新于2025-09-19 17:13:59
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Magnesium-Based Metasurfaces for Dual-Function Switching between Dynamic Holography and Dynamic Color Display
摘要： Metasurface-based color display and holography have greatly advanced the state of the art display technologies. To further enrich the metasurface functionalities, recently a lot of research endeavors have been made to combine these two display functions within a single device. However, so far such metasurfaces have remained static and lack tunability once the devices are fabricated. In this work, we demonstrate a dynamic dual-function metasurface device at visible frequencies. It allows for switching between dynamic holography and dynamic color display, taking advantage of the reversible phase-transition of magnesium through hydrogenation and dehydrogenation. Spatially-arranged stepwise nanocavity pixels are employed to accurately control the amplitude and phase of light, enabling the generation of high-quality color prints and holograms. Our work represents a paradigm towards compact and multifunctional optical elements for future display technologies.
关键词： magnesium,metasurfaces,color display,holography,multifunction
更新于2025-09-19 17:13:59
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Electron holography for vortex beams
摘要： A combined technology of vortex beam technique and electron holography has been developed. A range of about 10 times the diameter of the grating opening was irradiated and electron holography, electron vortex beam, orbital angular momentum, helical wavefront, wave propagation two-wave interference between a Bragg diffraction wave as a vortex beam and transmitted wave from and around a fork-shaped grating was recorded as a hologram. Reconstruction by using the Fourier transform method has been simultaneously performed for amplitude and phase distributions. Furthermore, by using a wave aberration function, amplitude and phase distributions at various propagation positions were reconstructed numerically, resulting in confirmation of vortex beam twists.
关键词： helical wavefront,electron holography,electron vortex beam,orbital angular momentum,wave propagation
更新于2025-09-19 17:13:59
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Multispectral incoherent holography based on measurement of differential wavefront curvature
摘要： We propose a technique of multispectral incoherent holography. The differential wavefront curvature is measured, and the principle of Fourier transform spectrometry is applied to provide a set of spectral components of three-dimensional images and continuous spectra for spatially incoherent, polychromatic objects. This paper presents the mathematical formulation of the principle and the experimental results. Three-dimensional imaging properties are investigated based on an analytical impulse response function. The experimental and theoretical results agree well.
关键词： Impulse response function,Multispectral imaging,Depth resolution,3D imaging property,Spectroscopy,Incoherent holography
更新于2025-09-19 17:13:59