Coherent Light Research Articles

Prognostic Significance of Biointegration at the Optic-Cornea Joint in Keratoprosthesis Implantation.

The purpose of this study was to characterize the morphological and immunological aspects of biointegration at the optic-cornea joint of a second-generation synthetic corneal device. The initial prototype, single-piece optic-skirt configuration, is constructed from compact and flexible perfluoroalkoxy alkane with porous expanded polytetrafluoroethylene (ePTFE) overlying the skirt to allow skirt-cornea biointegration. The second-generation version was modified to add ePTFE around the optic wall to allow optic-cornea biointegration. Initial and amended second-generation devices were implanted into healthy rabbit eyes. Clinical examination, anterior segment optical coherence tomography, light microscopy, and immunofluorescence studies were performed to assess structural integrity and determine molecular signatures indicative of inflammation and tissue remodeling between the 2 prototypes. Recipient eyes with both device versions showed no epithelial defects or tissue retraction at 3 months postoperatively. Optical coherence tomography images demonstrated no appreciable perioptic space with either prototype. Histopathology of the initial device demonstrated lack of stromal adhesion at the optic-cornea joint with epithelium filling the perioptic space. Second-generation devices demonstrated full sealing of the recipient stroma along the optic stem. Although the routine histopathology did not demonstrate inflammatory cells in the recipient cornea with either device, immunohistochemistry stains demonstrated quiescent phenotype of stromal and epithelial cells only in the second-generation devices. Biointegration between the synthetic corneal device and recipient tissue at the optic-cornea joint seems to avert inflammation and may help prevent sterile tissue lysis and prolong retention.

A Repeating Fast Radio Burst Source in a Low-luminosity Dwarf Galaxy

We present the localization and host galaxy of FRB 20190208A, a repeating source of fast radio bursts (FRBs) discovered using CHIME/FRB. As part of the Pinpointing REpeating ChIme Sources with EVN dishes repeater localization program on the European VLBI Network (EVN), we monitored FRB 20190208A for 65.6 hr at ∼1.4 GHz and detected a single burst, which led to its very long baseline interferometry localization with 260 mas uncertainty (2σ). Follow-up optical observations with the MMT Observatory (i ≳ 25.7 mag (AB)) found no visible host at the FRB position. Subsequent deeper observations with the Gran Telescopio Canarias, however, revealed an extremely faint galaxy (r = 27.32 ± 0.16 mag), very likely (99.95%) associated with FRB 20190208A. Given the dispersion measure of the FRB (∼580 pc cm−3), even the most conservative redshift estimate ( zmax∼0.83 ) implies that this is the lowest-luminosity FRB host to date (≲108 L ⊙), even less luminous than the dwarf host of FRB 20121102A. We investigate how localization precision and the depth of optical imaging affect host association and discuss the implications of such a low-luminosity dwarf galaxy. Unlike the other repeaters with low-luminosity hosts, FRB 20190208A has a modest Faraday rotation measure of a few tens of rad m−2, and EVN plus Very Large Array observations reveal no associated compact persistent radio source. We also monitored FRB 20190208A for 40.4 hr over 2 yr as part of the Extragalactic Coherent Light from Astrophysical Transients repeating FRB monitoring campaign on the Nançay Radio Telescope and detected one burst. Our results demonstrate that, in some cases, the robust association of an FRB with a host galaxy will require both high localization precision and deep optical follow-up.

Effect of tube debonding on the enamel surface in vitro : Evaluation with optical coherence tomography.

In vitro evaluation of the morphology of the enamel surface before bonding metal tubes and after debonding using spectral domain optical coherence tomography (SD-OCT) and light microscopy. In all, 40 extracted caries-free human molars without defects were selected and cleaned. The tooth surfaces were imaged by light microscopy and SD-OCT prior to the placement of metal tubes (Titanium Orthos; Ormco, Brea, CA, USA). The metal tubes were bonded to the teeth using four adhesive systems: group1) BrackFix Primer SE with BrackFix adhesive, group2) BrackFix Primer with BrackFix adhesive (VOCO, Cuxhaven, Germany), group3) Transbond Plus SE Primer with Transbond XT adhesive, group4) Transbond XT Primer with Transbond XT adhesive (reference, 3M Deutschland, Neuss, Germany). After tube removal, the bonded areas were imaged by light microscopy and/or OCT and evaluated according to the following four criteria: (1) depth of cohesive enamel defect, (2) enamel cracks, (3) adhesive residue after tube removal, and (4) adhesive residues after polishing. None of the groups had enamel defects or enamel cracks. Group1 showed significantly less adhesive residue after tube removal than the other groups (pi ≤ 0.014). There were no significant differences between the groups for adhesive residues after polishing (pi ≥ 0.628). Adhesive residues, if present, were only detectable by OCT and covered less than 1% of the enamel surfaces evaluated. Tube removal did not cause clinically relevant enamel damage such as chipping or cracking.

Interferometric Near-field Fano Spectroscopy of Single Halide Perovskite Nanoparticles.

Semiconducting halide perovskite nanoparticles support Mie-type resonances that confine light on the nanoscale in localized modes with well-defined spatial field profiles yet unknown near-field dynamics. We introduce an interferometric scattering-type near-field microscopy technique to probe the local electric field dynamics at the surface of a single MAPbI3 nanoparticle. The amplitude and phase of the coherent light scattering from such modes are probed in a broad spectral range and with high spatial resolution. In the spectral domain, we uncover a Fano resonance with a 2π phase jump. In the near-field dynamics, this Fano resonance gives rise to a destructive interference dip after a few femtoseconds. Mie theory suggests that the interference between electric quadrupole and magnetic dipole modes of the particle, with spectra affected by resonant interband absorption of MAPbI3, lies at the origin of this effect. Our results open up a new approach for probing local near-field dynamics of single nanoparticles.

Geometric phase for a nonstatic coherent light wave: nonlinear evolution harmonized with the dynamical phase

Geometric phase for a nonstatic coherent light wave: nonlinear evolution harmonized with the dynamical phase

Ultra-weak photon emission from DNA

It is conventionally believed that macromolecules found in living cells, including DNA, RNA, and proteins, do not exhibit inherent light emission. However, recent studies have challenged this concept by demonstrating spontaneous light emission from nucleic acids under certain conditions and physiological temperatures. By noninvasive monitoring of barley genomic DNA and advanced statistical physics analyses, temperature-induced dynamic entropy fluctuations and fractal dimension oscillations were identified at a key organizational threshold. The study revealed evidence for non-equilibrium phase transitions, a noticeable photovoltaic current jump at zero bias voltage, and a proportional increase (scaling) of the photoinduced current corresponding to increasing amounts of DNA. In addition, we estimated DNA’s energy production rate at criticality and introduced an interferometer using coherent light emissions from the DNA-water interface. These findings suggest that DNA is a major source of ultraweak photon emission in biological systems.

An improved version of PyWolf with multithread-based parallelism support

PyWolf is an open-source software with a graphical user interface that performs numerical simulations of the cross-spectral density function propagation of planar sources using parallel computation through PyOpenCL. In the previous versions of PyWolf, the user could select the OpenCL devices and platforms to perform the parallel computations on several tasks, except for that related to the two-dimensional (2D) fast Fourier transform (FFT) algorithm. The latter task can have a large computation time since one has to perform a large amount of 2D FFTs over 2D slices of a four-dimensional array. The option of using multithread-based computation on these loops and other tasks can be an advantage for multi-core CPUs and can significantly decrease the computation time. Here, I present version 3.0.0 of PyWolf, which adds a multithreading option to be used for the 2D FFT computations. This multithreading option can also be easily implemented in other time-consuming tasks. New version program summaryProgram Title: PyWolfCPC Library link to program files:https://doi.org/10.17632/frjscxypkd.3Developer's repository link:https://github.com/tiagoecmagalhaes/PyWolfLicensing provisions: GPLv3Programming language: PythonSupplementary material: Overview of the main changes with performance results.Journal reference of previous version: Comput. Phys. Commun. 294 (2024) 108899.Reasons for the new version: In the original paper of PyWolf [1] and in the previous version [2], parallel computation was performed only using PyOpenCL. However, in some cases where multiple cores are available in the CPU, multithreading [3] can significantly decrease the computation time of some tasks, for instance, the loops of 2D fast Fourier transforms (FFTs). This new version includes a built-in option for multithreading, enabling users to select the number of threads to be used in the numerical simulation.Summary of revisions: Multithreading support was added to PyWolf and users can now select this feature in PyWolf's graphical user interface and choose the number of available threads to be used in the simulation. In the current version, multithreading is only used for the loops of 2D FFTs but can be easily extended to other tasks. Other small features have been added and some issues have been corrected, namely: (i) a requirements file has been added listing all the libraries used; (ii) some errors associated with file paths have been corrected.Nature of problem: Propagation of partially coherent light from planar sources in the Fresnel or far field approximations using four-dimensional arrays [4,5] demands large memory and computation time. PyWolf uses PyOpenCL to perform parallel computation to reduce time-consuming calculations in the propagation of the cross-spectral density function [4], restricting the memory capacity as the main limitation.Solution method: The open-source toolkit PyOpenCL along with multithreading is used to decrease the computation time. Users can modify and add more features to PyWolf, such as source, propagation, and geometrical models. Custom-made optical components can also be added (e.g., lenses and apertures). The PyQt5-based graphical user interface enables users to easily set the input parameters to simulate their optical setup, plot and export the simulated results, and save or load the simulation session.

Accelerating data acquisition with FPGA-based edge machine learning: a case study with LCLS-II

Abstract New scientific experiments and instruments generate vast amounts of data that need to be transferred for storage or further processing, often overwhelming traditional systems. Edge Machine Learning (EdgeML) addresses this challenge by integrating
Machine Learning (ML) algorithms with edge computing, enabling real-time data processing directly at the point of data generation. EdgeML is particularly beneficial for environments where immediate decisions are required, or where bandwidth and
storage are limited. In this paper, we demonstrate a high-speed configurable ML model in a fully customizable EdgeML system using a Field Programmable Gate Array (FPGA). Our demonstration focuses on an angular array of electron spectrometers,
referred to as the ’CookieBox,’ developed for the Linac Coherent Light Source II (LCLS-II) project. The EdgeML system captures 51.2 Gbps from a 6.4 GS/s analog to digital converter and is designed to integrate data pre-processing and ML inside an
FPGA. Our implementation achieves an inference latency of 0.2 μs for the ML model, and a total latency of 0.4 μs for the complete EdgeML system, which includes preprocessing, data transmission, digitization, and ML inference. The modular design of
the system allows it to be adapted for other instrumentation applications requiring low-latency data processing.

Advancements in halide perovskite photonics

Halide perovskites have emerged as a new class of materials for photoelectric conversion, attracting an ever-increasing level of attention within the scientific community. These materials are characterized by expansive compositional choices, ease of synthesis, an impressively high light absorption coefficient, and extended carrier recombination lifetimes. These attributes make halide perovskites an ideal candidate for future optoelectronic and photonic applications, including solar energy conversion, photodetection, electroluminescence, coherent light generation, and nonlinear optical interactions. In this review, we first introduce fundamental concepts of perovskites and categorize perovskite photonic devices by the nature of their fundamental mechanisms, i.e., photon-to-electron conversion devices, electron-to-photon conversion devices, and photon-to-photon devices. We then review the significant progress in each type of perovskite device, focusing on working principles and device performances. Finally, future challenges and outlook in halide perovskite photonics will be provided.

Self-focusing and stimulated Brillouin scattering effect of low-temporal coherence light and corresponding damage characteristics in fused silica

Laser-induced damage thresholds (LIDTs) of input/exit surfaces and filamentation of fused silica under low-temporal coherence light (LTCL) and a corresponding damage mechanism are investigated. By comparing self-focusing effects of fused silica for each incident laser, the lower LIDT of filamentation damage under LTCL irradiation is mainly attributed to stronger self-focusing than traditional single longitudinal mode (SLM) pulse lasers. Meanwhile, differences in LIDTs for input/exit surfaces by LTCL and SLM pulse laser irradiation are attributed to self-focusing effects and backward stimulated Brillouin scattering. Finally, influences of fused silica thickness and incident laser polarization on LIDT are demonstrated. The research contributes to exploring safe boundaries for fused silica application in high-power LTCL devices.

Single-shot quantitative differential phase contrast microscope using a single calcite beam displacer

This paper presents the development of a single-shot, partially spatially coherent quantitative differential phase contrast microscopy (Q-DPCM) system. The optical scheme comprises a polarizer, lenses, calcite beam displacer, and analyzer, which can be seamlessly integrated to an existing bright-field microscopy system, transforming it into a Q-DPCM system. It utilizes a partially spatially coherent light source, enabling single-shot quantitative differential phase recovery of the specimens with high spatial phase sensitivity. It generates highly sensitive quantitative differential phase images of the specimens along one direction, like a gradient light interference microscopy (GLIM) system, using only a single interferogram. First, we validated the differential phase measurement capability of the system through experiments on polystyrene spheres (diameter 5.2 µm) and HeLa cells. Next, the system is utilized to generate quantitative phase maps of human red blood cells using two orthogonal differential interferograms recorded at two orientations of the calcite beam displacer. Further, the Q-DPCM system is implemented for 1-h time-lapse live cell monitoring, revealing the dynamics of intracellular granules such as nucleolus and lipids in U2OS cells.

High topological charge lasing in quasicrystals.

Photonic modes exhibiting a polarization winding akin to a vortex possess an integer topological charge. Lasing with topological charge 1 or 2 can be realized in periodic lattices of up to six-fold rotational symmetry-higher order charges require symmetries not compatible with any two-dimensional Bravais lattice. Here, we experimentally demonstrate lasing with topological charges as high as -5, +7, -17 and +19 in quasicrystals. We discover rich ordered structures of increasing topological charges in the reciprocal space. Our quasicrystal design utilizes group theory in determining electromagnetic field nodes, where lossy plasmonic nanoparticles are positioned to maximize gain. Our results open a new path for fundamental studies of higher-order topological defects, coherent light beams of high topological charge, and realizations of omni-directional, flat-band-like lasing.

High‐Fidelity Information Transmission Through the Turbulent Atmosphere Utilizing Partially Coherent Cylindrical Vector Beams

As the demand for high‐capacity and high‐fidelity communication systems continues to increase, addressing the challenges posed by noise and atmospheric turbulence disturbances is imperative. This study introduces and experimentally implements a novel free‐space optical communication protocol. This protocol combines the advantages of reducing the spatial coherence of light at the source with the capabilities of convolutional neural networks at the receiver to encode and transmit optical images through a noisy link. Light beams that are robust against noise are generated and atmospheric turbulence is modeled in a laboratory setting by decreasing the degree of spatial coherence of the source. Eight orbital angular momentum states, four polarizations, and eight coherence states of a light source that generates partially coherent cylindrical vector beams are utilized. These elements are employed to achieve a 256‐ary encoding/decoding data transmission within our protocol. This study is expected to catalyze further research into the utilization of partially coherent light and neural networks in the realm of free‐space optical communications.

Interference effects in commercially available free-space silicon single-photon avalanche diodes

Single-photon avalanche diodes (SPADs) are essential for photon-based measurements and metrology, enabling measurement comparisons at the few-photon level and facilitating global traceability to the SI. A spatially uniform detector response is crucial for these applications. Here, we report on interference effects in commercially available silicon SPADs that are detrimental to their spatial uniformity. Contrasts as high as 18% are observed, posing problems for metrology and general applications that utilize coherent light and require stable detection efficiencies. We eliminate the device optical window as a contributing interface, isolating likely causes to anti-reflective coatings, the semiconductor surface, and the SPAD's internal structure. We also present results where we leverage this sub-optimal behavior by aligning an incident beam with the position of maximum constructive interference, yielding an effective detection efficiency of 51.1(1.7)% compared to the normal value of 44.3(1)% obtained with the interference suppressed. We anticipate that this work will significantly impact the continuing development of these devices, the methods for characterizing them, and their use in accurate measurements.

Phase Space Formulation of Light Propagation on Tilted Planes

The solution of the Helmholtz equation describing the propagation of light in free space from a plane to another can be described by the angular spectrum operator, which acts in the frequency domain. Many applications require this operator to be generalized to handle tilted source and target planes, which has led to research investigating the implications of these adaptations. However, the frequency domain representation intrinsically limits the understanding the way the signal is transformed through propagation. Instead, studying how the operator maps the space–frequency components of the wavefield provides essential information that is not available in the frequency domain. In this work, we highlight and exploit the deep relation between wave optics and quantum mechanics to explicitly describe the symplectic action of the tilted angular spectrum in phase space, using mathematical tools that have proven their efficiency for quantum particle physics. These derivations lead to new algorithms that open unprecedented perspectives in various domains involving the propagation of coherent light.

Generation of non-Gaussian states of light using deterministic photon subtraction

Abstract We explore a recently demonstrated deterministic photon subtraction scheme, based on single-photon Raman interaction with a Λ-type three-level atom, as a tool for manipulating quantum state of few-photon light pulses. We establish a comprehensive theoretical framework using input–output formalism and quantum regression theorem, enabling calculation of the first order autocorrelation matrices of the output light and identification of the temporal modes present in the generated light via their eigendecomposition. By modeling the entire system as a quantum network consisting multiple virtual cavities and a lambda-type emitter cascaded in two parallel guided modes of opposite propagation directions, we extract the quantum state occupying the modes of interest. For both squeezed vacuum and coherent light input pulses, the Wigner function of the output light after photon subtraction clearly reveals its non-Gaussian character. Furthermore, we propose a measurement-based scheme on the subtracted photon which can lead to conditional generation of quantum states resembling Schrodinger’s kitten state directly from coherent input light with fidelities above 99%. This result is particularly nothworthy, as coherent pulses, unlike the squeezed vacuum inputs commonly used in previous studies, are readily available in most experimental setups.

Revealing and Manipulating Hidden Fine-Structure Coherence of Bright Excitons in CsPbI3 Perovskite Quantum Dots.

Observation and understanding of fine-structure splitting of bright excitons in lead halide perovskite quantum dots (QDs) are crucial to their emerging applications in quantum light sources and exciton coherence manipulation. Recent studies demonstrate that ensemble-level polarization-resolved transient absorption spectroscopy can reveal the quantum beats arising from the coherence between two fine-structure levels. Here we report the observation of an extra fine-structure quantum coherence hidden in previous studies by using cryo-magnetic quantum beat spectroscopy. In ∼6 nm CsPbI3 QDs, two splitting energies of 0.25 and 1.20 meV were observed at 1.7 K, which gradually increased to 0.74 and 1.55 meV, respectively, when a longitudinal magnetic field up to 7 T was applied. The field dependence allowed us to extract two distinct nominal Landé g-factors corresponding to QDs with different orientations with respect to the external field.

Coherent artifact-free optical profilometry with improved space bandwidth product using partially spatially coherent light

Coherent artifact-free optical profilometry with improved space bandwidth product using partially spatially coherent light

Characterization of Defocused Coherent Imaging Systems with Periodic Objects.

Recent advancements in quantum and quantum-inspired imaging techniques have enabled high-resolution 3D imaging through photon correlations. These techniques exhibit reduced degradation of image resolution for out-of-focus samples compared to conventional methods (i.e., intensity-based incoherent imaging). A key advantage of these correlation-based approaches is their independence from the system numerical aperture (NA). Interestingly, both improved resolution of defocused images and NA-independent scaling are linked to the spatial coherence of light. This suggests that while correlation measurements exploit spatial coherence, they are not essential for achieving this imaging advantage. This discovery has led to the development of optical systems that achieve similar performance by using spatially coherent illumination and relying on intensity measurements: direct 3D imaging with NA-independent resolution was recently demonstrated in a correlation-free setup using LED light. Here, we explore the physics behind the enhanced performance of defocused coherent imaging, showing that it arises from the modification of the sample's spatial harmonic content due to diffraction, unlike the blurring seen in conventional imaging. The results we present are crucial for understanding the implications of the physical differences between coherent and incoherent imaging, and are expected to pave the way for the practical application of the discovered phenomena.

Unidirectional imaging with partially coherent light

Unidirectional imaging with partially coherent light