Light Source Research Articles

Resonance modes in microstructured photonic waveguides: efficient and accurate computation based on AAA rational approximation

Abstract We present a framework for the efficient and accurate computation of resonance modes in photonic waveguides. The framework is based on AAA rational approximation with the application of special light sources. It allows one to calculate only relevant modes, such as the fundamental resonance modes localized in the central core of the waveguides. We demonstrate the framework using an example from the literature, a hollow-core photonic crystal fiber. This waveguide supports many other modes, such as cladding modes and higher-order modes. These nonrelevant modes are not calculated, so that challenging post-processing with mode filtering is not required.

Cavity-based compact light source for extreme ultraviolet lithography

A critical technology for high-volume manufacturing of nanoscale integrated circuits is a high-power extreme ultraviolet (EUV) light source. Over the past decades, laser-produced plasma (LPP) sources have been actively utilized in this field. However, current LPP light sources may provide insufficient average power to enable future manufacturing at the 3 nm node and below. In this context, accelerator-based light sources are considered to be promising tools for EUV lithography. This paper proposes a regenerative amplifier free-electron laser EUV source with harmonic lasing, driven by a superconducting energy-recovery linac (ERL). By utilizing the nth harmonic, the required electron beam energy is reduced to 1/n of that in conventional schemes. The proposed configuration, employing an electron beam energy of approximately 0.33 GeV with a short-period (16 mm) undulator, is estimated to provide an average EUV power of about 2 kW. This approach significantly reduces the required electron energy and facility size relative to other accelerator-based proposals, thereby offering new possibilities for constructing high-power EUV sources with low-energy ERLs. Published by the American Physical Society 2025

Chiral flatband in refractive index modulated metasurfaces

Flatband exhibits unique properties, such as slow light effects and a high density of states; incorporating these properties into chiral metasurfaces can significantly enhance chiroptical responses across a range of incident angles. In this study, we establish a theoretical framework to analyze circular dichroism in the presence of broken mirror symmetry along the z-direction. Building on this framework, we employ a theoretical model based on refractive index modulation and partial etching, which lead to a metasurface with a pronounced flatband with chiroptical response. This metasurface holds significant potential for applications in chiral light source emission and detectors, chiral sensing, and enantioseparation, particularly at wide incidence angles.

Multi-Beam-Energy Control Unit Based on Triple-Bend Achromats

X-ray free electron lasers (XFELs) are the new generation of particle accelerator-based light sources, capable of producing tunable, high-power X-ray pulses that are increasingly vital across various scientific disciplines. Recently, continuous-wave (CW) XFELs driven by superconducting linear accelerators have garnered significant attention due to their ability to enhance availability by supporting multiple undulator lines simultaneously. In this paper, we introduce a novel delay system comprising four triple-bend achromats (TBAs). This delay system was combined with fast kickers and can be employed to generate electron beams on a bunch-to-bunch basis in a CW-XFEL facility. Based on the parameters of the Shanghai High-Repetition-Rate XFEL and Extreme Light Facility, start-to-end simulations demonstrate that the TBA-based delay system achieves excellent electron beam qualities while providing a wide beam-energy-tuning range from 1.39 to 8 GeV.

Colour discrimination evaluation under multiple light sources using signal detection theory

Colour discrimination evaluation under multiple light sources using signal detection theory

Generalized snapshot spectral imaging across different illuminants with wavelength-phase joint coding

Snapshot spectral imaging has been an active area of research and has attracted significant attention. However, few studies have considered the diversity of light sources, leading to overfitting on specific types of illuminants. In this paper, we propose an illuminant augmentation method to improve the generalization ability. The color filter arrays (CFAs) of RGB cameras can encode wavelength information to colors but meet metamerism. To tackle this issue, we further optimize a diffractive optics element (DOE) for phase coding in an end-to-end manner. We build a phase-wavelength joint coding compressive imaging system that shows better generalization ability than a conventional RGB camera. To enhance the spectral reconstruction performance, we introduce a novel mamba-based network, snapshot spectral compressive imaging mamba (SSCIM). Additionally, we have collected a well-calibrated hyperspectral dataset of relative reflectance for testing. Experimental results demonstrate that our method achieves state-of-the-art performance in hyperspectral reconstruction and illuminant generalization.

EasyVis: a real-time 3D visualization software system for laparoscopic surgery box trainer.

EasyVis is an emerging immersive 3D laparoscopic visualization system for improving the efficiency of laparoscopic surgery. It integrates multiple micro-cameras and light sources with the surgical ports to provide intra-abdominal stereo vision of surgery at a desired viewpoint. In this work, we develop a visualization algorithm using the EasyVis micro-camera array assembly in a laparoscopic surgery training box environment with simplified training tasks to validate the feasibility of this novel technology. Since most laparoscopic surgical tools are rigid-body objects, their 3D shape may be acquired offline. We developed 2D object detection and track algorithms to acquire the 2D pose of each object and a 3D fusion algorithm to estimate and track the 3D pose of each object using estimated 2D poses. Then, together with the acquired 3D model of each object, we are able to render each object at a desired view using the 3D surface model (acquired offline) and images acquired from individual micro-cameras. In addition to the foreground rigid objects, the background 3D model is acquired using structured lights and structure from motion. The background is assumed to be slowly varying compared to the rapid motion of the foreground objects. As such, the background 3D model needs to be updated only occasionally. Our rendering algorithm is capable of integrating the foreground and background 3D models to facilitate image-based rendering from a desirable viewing angle. We performed experiments to validate the accuracy and quality of the rendered images.

Application of Cascaded TFBG for Wavelength-Shift-Based SRI Measurement with Reduced Polarization Cross-Sensitivity

The wavelength shift in TFBG cladding resonance is a practical parameter due to its independence from power fluctuations coming from the light source or fiber bends. It is possible to select the cladding modes that are characterized by the center wavelength shifts while changing the refractive index of the surrounding medium. In the case of a single TFBG, this parameter is strongly dependent on the input light polarization angle. In this paper, we present the possibility of reducing interference of polarization changes to measure the refractive index by using the wavelength shift in Bragg grating cladding modes with the cascade structure called the perpendicular TFBG (P-TFBG). The wavelength shift in the selected cladding mode was analyzed and compared in the case of a single grating and proposed cascade. In the case of P-TFBG, the dependence on the corresponding cladding mode of a single TFBG with the same inscription parameters is reduced to 16.15%. The analysis of mode wavelength instead of the previously reported amplitude provides a wider measurement range of possible SRI and protects the results from power fluctuations.

Space disinfection using TiO2 photocatalyst reduces the incidence of febrile neutropenia in cancer patients

Febrile neutropenia (FN) is life-threatening condition, and airborne microorganisms have been identified as one of the potential transmission routes. The objective of this study was to evaluate spatial sterilization using photocatalytic oxidative decomposition reactions which are effective to prevent FN. An air purifier equipped with a platinum-added titanium dioxide photocatalytic and LED light source (LED-TiO2 device) was installed in hospital rooms (per 21.5–35 m3) to investigate changes in FN incidence and airborne microorganism counts. Airborne microorganisms in the hospital rooms matched those responsible for nosocomial infections. The incidence of FN was significantly reduced after installation of the LED-TiO2 device [9/13 vs. 2/12, P-value (P) = 0.015]. The LED-TiO2 device decreased the number of airborne microorganisms in patient-free rooms by approximately 75% after 2 h [P < 0.001]. When patient was in the room, the number of airborne microorganisms increased with medical procedure. However, after 20 min of procedure, the number of airborne microorganisms was approximately 50% lower than without the device room [P = 0.019]. The LED-TiO2 device successfully achieved spatial disinfection of hospital rooms, and reduced the incidence of FN. Spatial disinfection using photocatalysts is considered an effective new infection prevention measure for patients with severe neutropenia undergoing cancer treatment.

Electrophotocatalysis for Reductive Defluorination of PTFE and PFASs.

Polytetrafluoroethylene (PTFE) is among the most inert poly- and perfluoroalkyl substances (PFASs) and its degradation under mild conditions remains underdeveloped. We report a supercapacitor assisted electrophotocatalysis, incorporating the strength of both electrochemical and photochemical energy, for the efficient defluorination of PTFE and other PFASs at low temperature. CBZ6 worked as a photoreductant for injecting electrons to the inert carbon-fluorine bond, whereas the supercapacitor enabled the generation of the catalytically active species via an electrochemical process. Furthermore, the utilization of sunlight as the light source and supercapacitor as the electrical energy source makes the reaction portable and enables its outdoor applications.

Visualizing Molybdenum Pentachloride Flow During Vapor Deposition Processes Using Absorption Imaging.

An absorption imaging technique was described for visualizing molybdenum pentachloride (MoCl5) flow during an atomic layer deposition/pulsed chemical vapor deposition process. The imaging system was composed of a telecentric lens and a commercial 7.1 megapixels (MP) complementary metal oxide semiconductor (CMOS) camera. The light source was a fiber-coupled light emitting diode operating at a peak emission wavelength of 443 nm. Flow images of MoCl5 vapor entrained in a carrier gas were recorded at approximately 93 frames per second in a research-grade vapor deposition chamber. The utility of this technique was illustrated by comparing the MoCl5 flow patterns for two precursor injection conditions, conditions consisting of different argon carrier gas flow rate and chamber pressure. For a low flow rate and chamber pressure, the flow images showed a gradual expansion of the MoCl5 concentration front through the field of view with a relatively short MoCl5 residence time. These flow patterns result in a relatively uniform precursor concentration front impinging on the wafer surface with the precursor being efficiently exhausted from the chamber, making these conditions desirable for thin film deposition in this chamber. For a high carrier gas flow rate and elevated chamber pressure, the flow images showed a high gas velocity jet impinging on the wafer chuck surface and the formation of gas recirculation zones, resulting in a relatively long residence time. These flow conditions would make it difficult to reproducibly deposit uniform thin films in this chamber. This comparison demonstrated the utility of this technique for qualitative characterization of precursor flow fields with minimal data processing. However, the two-dimensional data obtained from this technique can also provide the basis for training and validating computational fluid dynamics models. Furthermore, the addition of duplicate optical systems would provide the basis for determining the three-dimensional precursor distribution through tomographic analysis.

Highly Efficient Indoor Perovskite Solar Cells with 40% Efficiency Using Perylene Diimide-Based Zwitterionic Cathode Interlayers.

Metal halide perovskites are ideal candidates for indoor photovoltaics (IPVs) due to their tunable bandgaps, which allow the active layers to be optimized for artificial light sources. However, significant non-radiative carrier recombination under low-light conditions has limited the full potential of perovskite-based IPVs. To address this challenge, an integration of perylene diimide (PDI)-based sulfobetaines as cathode interlayers (CILs) is proposed and the impact of varying alkyl chain length (from 1,2-ethylene to 1,5-pentylene) between the cationic and the anionic moieties is examined. The respective four PDI materials are synthesized almost qualitatively using a one-step microwave-assisted process. All of them show adequate thermal stability and energy levels suitable for the desired application as CILs. Moreover, their degradation temperature, LUMO level, conductivity, and performance in model devices are found to change positively along with the alkyl chain length increase. Among the tested derivatives, the compound equipped with the longest alkyl chain (PDI-C5-S3) stands out for its superior electrical conductivity and enhanced ability to lower the silver cathode work function. When incorporated into Cs0.18FA0.82Pb(I0.8Br0.2)-based wide-bandgap perovskite solar cells (PSCs), the PDI-C5-S3 interlayer lead to an outstanding power conversion efficiency (PCE) of 19.04% under one-sun illumination and a remarkable 40.72% under 3000K LED (1000 lux) conditions.

Deep-learning real-time phase retrieval of imperfect diffraction patterns from X-ray free-electron lasers

Machine learning is attracting surging interest across nearly all scientific areas by enabling the analysis of large datasets and the extraction of scientific information from incomplete data. Data-driven science is rapidly growing, especially in X-ray methodologies, where advanced light sources and detection technologies produce vast amounts of data that exceed meticulous human inspection capabilities. Despite the increasing demands, the full application of machine learning has been hindered by the need for data-specific optimizations. In this study, we introduce a new deep-learning-based phase retrieval method for imperfect diffraction data. This method provides robust phase retrieval for simulated data and performs well on partially damaged and noisy single-pulse diffraction data from X-ray free-electron lasers. Moreover, the method significantly reduces data processing time, facilitating real-time image reconstructions that are crucial for high-repetition-rate data acquisition. This approach offers a reliable solution to the phase problem to be widely adopted across various research areas confronting the inverse problem.

LightViz: autonomous light-field sensing, mapping, and assessment for distributed light pollution monitoring.

Existing technologies for distributed light-field mapping and light pollution monitoring (LPM) rely on either remote satellite imagery or manual light surveying with single-point sensors such as SQMs (sky quality meters). These modalities offer low-resolution data that are not informative for dense light-field mapping, pollutant identification, or sustainable policy implementation. In this work, we propose LightViz-an interactive software interface to survey, simulate, and visualize light pollution maps in real time. As opposed to manual error-prone methods, LightViz (i) automates the light-field data collection and mapping processes; (ii) provides a platform to simulate various light sources and intensity attenuation models; and (iii) facilitates effective policy identification for conservation. To validate the end-to-end computational pipeline, we design a distributed light-field sensor suite, collect data on Florida coasts, and visualize the distributed light-field maps. In particular, we perform a case study at St. Johns County in Florida, which has a two-decade conservation program for lighting ordinances. The experimental results demonstrate that LightViz can offer high-resolution light-field mapping and provide interactive features to simulate and formulate community policies for light pollution mitigation. We also propose a mathematical formulation for "light footprint" evaluation, which we integrated into LightViz for targeted LPM in vulnerable communities. LightViz system design and software is available at https://robopi.ece.ufl.edu/lightviz.html .

Electrochemiluminescence Microscopy in Nano‐Electrochemistry Research: Unraveling the Underlying Principles, Tracing the Evolutionary Developments, and Charting the Prospective Trajectories

AbstractElectrochemical technology provides unique opportunities to create an environment‐friendly and sustainable chemical industry. Nano‐electrochemistry offers valuable insights into the comprehension of electrochemical mechanisms and behaviors at the nanoscale, as opposed to complex ensemble systems. Despite the use of various analytical tools, such as nanopore technology and scanning probe microscopy, for nano‐electrochemical research, direct operando and high‐throughput spatially resolved electrochemical measurements remain challenging. Electrochemiluminescence (ECL) is an electrochemical reactions‐dependent luminescence process without external light sources. Coupled with a microscopy configuration, a novel imaging methodology ECL microscopy (ECLM), is developed. ECLM, due to its distinctive imaging mode, holds considerable potential in the field of nano‐electrochemistry. This review will initially present an overview of the basic principles of ECL. The next section will describe the design of the ECLM apparatus and discuss its diverse applications in nano‐electrochemistry. Finally, the challenges and outline of the prospects for further development of the ECLM technique will summarized.

150 Hybrid Heller's Myotomy: A Useful Approach When Difficulty Anticipated? A Retrospective Review

Abstract Background Laparoscopic myotomy for achalasia is complicated by mucosal perforation in up to 28% of primary procedures and up to 50% of reoperations, with 33% of patients experiencing failure due to inadequate myotomy. We hypothesised that laparoscopic Heller’s myotomy, with endoscopic surveillance of the oesophageal mucosa, via oesophago-gastro-duodenoscopy (OGD), would reduce the incidence of both. This study examined mucosal perforation rates, myotomy success, and long-term outcomes following this hybrid (HHM) technique. Methods The myotomy was performed laparoscopically, with concomitant OGD, to scrutinize mucosal integrity and muscle fibre division simultaneously during critical myotomy steps. Alternating light sources and luminal insufflation were used to confirm myotomy completeness. All operative records were reviewed, and symptomatic improvement was measured by Eckardt score at 5 years. Results Of the 35 procedures performed, none were complicated by intraoperative perforation. Of the 20 patients available for long term follow-up, 15 (75%) had an Eckardt score of ≤ 3 at 5 or more years of follow-up, with sustained symptomatic relief up to 16 years postoperatively. Two patients experienced recurrence of moderate-to-severe symptoms, and one patient experienced recurrence of moderate symptoms. Conclusion OGD surveillance during HHM virtually eliminates the risk of mucosal injury and incomplete myotomy. This HHM technique should be considered for high-risk patients, especially those undergoing redo-Heller’s myotomy or previously treated by per-oral endoscopic myotomy (POEM), to reduce risk of mucosal injury, incomplete myotomy and imperfect fundoplication, guaranteeing long term symptomatic relief in the majority of patients.

Optical fibers performance parameters management under the control of spectral functional light sources with various wavelength windows and thermal effects

Abstract This paper has clarified the high speed performance signature of single-mode/multimode graded index silica-doped fibers in point to point link transceiver communication system. Fiber signal attenuation is studied versus ultraviolet wavelength region and different germanium dopant ratios added to silica fibers in point to point link. The fiber signal attenuation is also clarified versus near infrared wavelength region and different germanium dopant ratios added to silica fibers in point to point link. Fiber scattering loss is demonstrated against spectral operating wavelength region and different thermal effects of fiber temperature in point to point link. The modal fiber dispersion is investigated clearly and clarified in relation to fiber numerical aperture at different relative refractive index difference at operating spectral wavelength of 1,550 nm and 1,300 nm near infrared regions.

Simulative study of light sources for enhancement of optical peak pulse power and energy with the management for time bandwidth product of an ultrashort optical pulse train

Abstract This paper highlighted the simulative study of the best selection of various light sources for the improvement of the optical peak pulse power and energy with the management for time bandwidth product of an ultrashort optical pulse train. Pulse duty cycle, rectangular/Gaussian pulse peak power, Sech pulse peak power, pulse separation, average pulse intensity, peak intensity and total pulse energy are measured against the pulse duration at 10 MHz repetition rate, 1 mW average power and 1 mm spot diameter. Pulse energy, average pulse intensity, and peak pulse intensity variations are clarified against the repetition rate and average power variations at 1 mm spot diameter. Time bandwidth product, Gaussian chirp parameter and Accumulated group delay dispersion variations are demonstrated versus spectral laser source wavelength and spectral width at 10 ns pulse duration. Time bandwidth product and Gaussian chirp parameter are also clarified against laser spectral line width at first/second/third/fourth spectral operating wavelength windows.

Multiplexing information limits in multi-beam ptychography

Ptychography is a lensless imaging technique where the sample is laterally scanned by the illuminating beam. In multi-beam ptychography multiple beams simultaneously illuminate the sample, enabling faster scanning of larger areas. In this work, we explore the potential of multi-beam ptychography with a large number of illumination channels to enhance imaging throughput. Our findings show that while spatial resolution is reduced compared to single-beam ptychography, multi-beam ptychography still significantly increases throughput. Using synthetic and experimental data, we demonstrate an almost fivefold improvement in throughput, accompanied by reduced memory footprint and overhead time. Furthermore, we present the successful implementation of massively multiplexed multi-beam ptychography with up to 64 channels. These results pave the way for efficient use of light sources with partial spatial or temporal coherence for ptychography, opening new possibilities for high-throughput imaging applications.

Emergent 2D van der Waals materials photonic sources

Abstract Over the past two decades, two-dimensional (2D) van der Waals (vdW) semiconductors have garnered significant attention in the field of light sources due to their unique optoelectronic properties, such as high excitonic binding energy, tunable bandgaps, and strong optical anisotropy. These properties make 2D vdW semiconductors highly promising for next-generation light sources, offering advantages like enhanced efficiency, wavelength tunability, and polarization control. In this review, we summarize the development of various 2D vdW material-based light sources and their modulation mechanisms. We first provide an overview of excitonic properties and light-emission principles that aim to develop light sources with low-power, high-efficiency. Next, we discuss advances in 2D semiconductor lasers, including intralayer and interlayer exciton lasers, cavity-free systems, and exciton-polariton sources. We then look into single-photon emission and their integration into on-chip systems, followed by studies on nonlinear optical properties like high-order harmonic generation and P-band emission. Additionally, we cover advancements in electrically pumped light sources. The review concludes with an outlook on future developments of 2D vdW semiconductor light sources.