Light Source Research Articles

Characterizing temporal stability of supercontinuum generation in higher-order modes supported by liquid-core fibers

The generation of tailored supercontinua is essential for studying ultrafast light-matter interactions and for a variety of practical applications requiring broadband light. Liquid-core fibers (LCFs) have emerged as an innovative nonlinear photonic platform, demonstrating high efficiency in nonlinear frequency conversion. In this study, we showcase that LCFs provide a stable platform for ultrafast supercontinuum generation in a selected higher-order vector mode at 1.55μm\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$1.55\\;\\upmu \\hbox {m}$$\\end{document}. Specifically, we demonstrate soliton fission and double-dispersive wave generation using a radially polarized mode in a CS2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\hbox {CS}_{2}$$\\end{document}-silica liquid-core fiber. The experiments were performed in a temperature-controlled laboratory, showing excellent stability with no evidence of fiber degradation, material degradation, or drift-induced changes in mode excitation over extended periods under standard environmental conditions. Our results confirm that liquid-core fibers are a reliable platform for nonlinear photonics, suitable for applications such as computationally tailored supercontinuum generation, single pulse spxectroscopy, and tailored light sources, all of which rely on consistent and stable nonlinear frequency conversion.

Research on the Flicker Effect in Modern Light Sources Powered by an Electrical Network

Disruptions in power quality have a negative impact on many energy consumers. These include lighting, where interference manifests itself, among others, in the form of light flickering. The article presents phenomena accompanying the operation of modern light sources against the background of exemplary results of studies on the flicker of conventional light sources, such as incandescent or fluorescent lamps. The flickering effect of light generated in modern lamps can occur under stable voltage conditions in the supply network. The main subjects of the conducted research were solid-state light sources—light-emitting diode (LED) lamps, currently available on the lighting market. To assess the effects of these phenomena, it is necessary to use measures other than those traditionally used. The method used allows for the measurement of flicker resulting from both power supply disturbances and the properties of modern light sources. Using the developed measurement system, it is possible to record temporal changes in flicker coefficients resulting from, for example, changing supply voltage conditions. Due to the possibility of flickering light from sources offered by different manufacturers, as shown by research, it is advisable to carry out measurements at the place of use of the lighting.

Flexible electrodes based on laser-induced graphene as an analytical platform to monitor amoxicillin

Graphene production methods are typically complex and include micromechanical exfoliation, reduction of graphene oxide in the liquid phase, and epitaxial growth. However, a more efficient and rapid alternative is the thermal conversion of polyimide into graphene by laser pyrolysis, offering a simpler and faster approach. Thus, this paper introduces an electrochemical platform based on laser-induced graphene generated from a visible light source to detect amoxicillin. For this purpose, a laboratory-constructed 3D-printer was utilized. In this setup, a visible laser source emitting at 449.2 nm with a maximum power output of 3.5 W was integrated into the extrusion nozzle of a fused deposition modeling 3D-printer to manufacture graphene electrodes from polyimide sheets. Subsequently, a differential pulse voltammetry method was proposed showing an oxidation peak at +0.52 V (vs Ag|AgCl|KCl(sat.)). The sensor exhibited a wide linear working range from 9.60 to 103.3 µmol L−1, a limit of detection of 5.4 μmol L−1, adequate precision (RSD < 7%), and recovery values of 90% to 107% when applied to milk samples, synthetic urine, and pharmaceutical formulations. The sensor is free from interference with other drugs commonly used in human and veterinary medicine. Herein, we report for the first time a robust, scalable, and inexpensive sensor based on a flexible substrate for the detection of amoxicillin in different matrices. It stands as an accessible possibility for routine analysis in clinical and pharmaceutical contexts.

High-entropy spinel oxide: Synthesis and photo-responsivity of Mn0.68Cr0.8Rh0.64Co0.87O4

Recently, there has been extensive research on modulating band structures using MnCr2O4, which has gained significant attention as a photocatalyst. However, due to thermodynamic constraints, conventional modulation of band structures using two compositions poses challenges. Therefore, we utilized a high-entropy approach to easily modulate band structures by forming multi-composition systems (three-composition oxides or higher). The spinel structure of Mn0.68Cr0.8Rh0.64Co0.87O4 produced via electrospinning enabled the fabrication of nano fibers with an average diameter of 160 nm at a calcination temperature of 900 °C, and these nano fibers were crystallized through various analytical instruments. Furthermore, nanofibers calcined at 900 °C exhibited high responsivity and fast rise, decay times under a light source with a wavelength of 635 nm. Thus, with such high reactivity, fast response time, and clear selectivity, Mn0.68Cr0.8Rh0.64Co0.87O4 indicates promising potential as a material for future photo-catalytic research.

Modeling and application of array light sources in ultraviolet communication systems

Reliable communication over long distances using ultraviolet (UV) light is challenging due to the strong scattering and atmospheric absorption of UV light. However, with advancements in UV LED technology, the performance of transmitters can be significantly enhanced by employing an array of light sources, which improves the overall quality of communication. Despite these advancements, the impact of various array configurations — such as shape, quantities, and other parameters — on light intensity distribution and UV optical communication remains largely unexplored. In this work, we first modeled the light intensity distribution of arrayed light sources with varying shapes, quantities, and other parameters. We improved the traditional Monte Carlo method to better accommodate these distributions, enabling more accurate simulations. Subsequently, we obtained simulation results for different array configurations. Building on these findings, we developed a UV LED array communication system that achieved a bit error rate (BER) of 10−6 for information transmission over a distance of 500 m. This research provides valuable insights into the long-distance transmission capabilities of UV light using arrayed light sources.

Rod-shaped LuAG:Ce transparent ceramic enabling ultrahigh forward efficiency for laser lighting in a transmissive mode.

Ceramic phosphors have high thermal conductivity and high thermal stability, showing great potential for use in laser lighting. However, it is difficult to further improve the forward efficiency in transmissive mode because of the arbitrarily emitting ceramic phosphors and light loss by secondary optical components. Here, an effective design of rod-shaped LuAG:Ce transparent ceramics was proposed, and the silicone encapsulated ceramic-based devices could operate stably under 3.5 W laser excitation, possessing a luminous efficiency of 150-180 lm/W, far exceeding the level of existing commercial transmissive mode. Besides, because of the gradual absorption of blue light and the gradient distribution of heat, the rod-shaped LuAG:Ce transparent ceramics could bear a power density of 46 W/mm2 without luminous saturation, and the thermal-induced luminous degradation only accounted for 7% under a 15 min operation. The ceramic-based laser lighting sources with low divergence angle (∼4°) and uniform spatial distribution were obtained. Our optimized transparent ceramic rod and encapsulation scheme provided a solution to improve the efficiency of a transmissive mode for laser lighting.

The interface between body and culture in the figurative conceptualization of the “eye” in Amharic

Abstract Inspired by the notions of body-based and culturally specific embodiment, this study sheds light on the interface between body and culture in the Amharic conceptualization of ayn ‘eye.’ Applying the “lexical approach”, this paper examines the eye-related metaphors in Amharic monolingual and bilingual dictionaries. At the bodily level, the widespread conceptual metaphors knowing/thinking is seeing and eyes are light sources, and the metonymies eye for person and physiological (eye) change stands for an emotion are present in Amharic. In the cultural dimension, ayn is related to the concept of the “evil eye”, which associates the eye with mystical powers. However, contrary to the widespread superstitious belief of the “evil eye” in other cultures, the notion of the “evil eye” in Amharic is associated with the concept of buda--a class of people socially segregated due to their economic status and their supposedly accursed lineage. This study shows that the presence of similar conceptual metaphors (“vision-light”, “vision-knowledge”, and “eye-emotion/personality” metaphors) and cultural beliefs (the “evil eye”) in different languages/cultures does not necessarily entail equivalent conceptualization.

Reusable Microfluidic Chambers for Single-Molecule Microscopy.

Maintaining a consistent environment in single-molecule microfluidic chambers containing surface-bound molecules requires laborious cleaning and surface passivation procedures. Despite such efforts, variations in nonspecific binding and background signals commonly occur across different chambers. Being able to reuse the chambers without degrading the surface promises significant practical and fundamental advantages; however, this necessitates removing the molecules attached to the surface, such as DNA, proteins, lipids, or nanoparticles. Biotin-streptavidin attachment is widely used for such attachments, as biotin can be readily incorporated into these molecules. In this study, we present single-molecule fluorescence experiments that demonstrate effective resetting and recycling of the chambers at least 10 times by using photocleavable biotin (PC-biotin) and UV-light exposure. This method differs from alternatives as it does not utilize any harsh chemical treatment of the surface. We show that all bound molecules (utilizing various PC-biotin attachment chemistries) can be removed from the surface by a 5 min UV exposure of a specific wavelength. Nonoptimal wavelengths and light sources showed varying degrees of effectiveness. Our approach does not result in any detectable degradation of surface quality as assessed by the nonspecific binding of fluorescently labeled DNA and protein samples and the recovery of the DNA secondary structure and protein activity. The speed and efficiency of the resetting process, the cost-effectiveness of the procedure, and the widespread use of biotin-streptavidin attachment make this approach adaptable for a wide range of single-molecule applications.

Effects of dim-evening lighting optimised for geographical orientation versus standard lighting on mental health: protocol paper for a quasiexperimental study in a psychiatric hospital

IntroductionResearch has provided novel insights into how light stimulates circadian rhythms through specialised retinal ganglion cells to the suprachiasmatic nucleus. In addition, there has been a revolution in light-emitting diode...

Development of a nanometre scale X-ray speckle-based CT technique through the 3-D histological assessment of an acute respiratory distress syndrome model

The study of biological soft tissue structures at the micron scale details the function of healthy and pathological tissues, which is vital in the diagnosis and treatment of diseases. Speckle based X-ray phase contrast tomographic scans at a nanometer scale have the potential to thoroughly analyse such tissues in a quantitative and qualitative manner. Diamond light source, the UKs national synchrotron facility developed and refined a 1-D X-ray speckle-based imaging technique, referred to as Fly scan mode. This novel image acquisition technique was used to perform a rapid structural composition scan of rodent lung histology samples. The rodent samples were taken from healthy and Staphylococcus aureus induced acute respiratory distress syndrome models. The analysis and cross comparison of the fly scan method, absorption-based tomography and conventional histopathology H&E staining microscopy are discussed in this paper. This analysis and cross comparison outline the ways the speckle-based technique can be of benefit. These advantages include improved soft tissue contrast, 3-D volumetric rendering, segmentation of specific gross tissue structures, quantitative analysis of gross tissue volume. A further advantage is the analysis of cellular distribution throughout the volumetric rendering of the tissue sample. The study also details the current limitations of this technique and points to ways in which future work on this imaging modality may progress.

Polarization self-modulation in a coaxially end-pumped orthogonally polarized laser

A scheme of orthogonally polarized laser (OPL) with polarization self-modulation (PSM) in the coaxial end-pumping configuration is proposed in this work. The gain medium consisted of two Nd:YVO4 crystals with orthogonal optical axes, and a quarter-wave plate served as a polarization-switching device. By rotating the electric vector during each cavity round trip, frequency degeneration and correlated operation of two polarization components were achieved. The polarization eigenstates in two orthogonal directions were analyzed using the Jones matrix and eigenequation. The spectral distribution was also briefly discussed based on thermal effects. The results showed that two eigenmodes located at 45° and 135° to the crystal axis, respectively, with a frequency difference equaled to half the free spectral range of the resonator. In the experiments, it was found for the first time that the modulation of eigenstates can be realized by adjusting pump parameters (including pump power, beam size, focusing position, and pump wavelength) and cavity anisotropy, which enables the manipulation of degree of polarization (DOP) and monitoring the resonator properties. Overall, tuning the laser polarization eigenstate offers a flexible method to switch the operational states of the OPL, including the longitudinal mode frequency difference, DOP, polarization angle, etc. It is believed this scheme provides a valuable reference to realize compact, high-beam-quality, and robust OPLs for applications such as dual-frequency light source development, precision measurement and polarization control.

Design of the Single Heterogeneous Quantum Dot Lasers Emitting 4 Wavelengths Using Combination‐Grating Technology

AbstractMulti‐wavelength light sources are crucial for high‐bandwidth silicon photonic chips. In this paper, a single heterogeneous quantum dot distributed feedback (DFB) laser emitting 4 wavelengths using the combination‐grating technology is designed. To the best of the knowledge, this is the first heterogeneously integrated quantum dot DFB laser that lases stable multi‐wavelength in a single cavity. When the etching depth, etching width, and total length of gratings are 100 , 550 nm, and 1 000 µm, respectively, 4‐wavelength with 1297.01 , 1303.38 , 1309.74 , and 1316.11 nm are obtained by varying the grating period from 196 to 199 nm with the spacing of 1 nm. Compared to the conventional DFB laser arrays, the DFB laser units are significantly reduced by 3/4 while maintaining the same number of output wavelengths. Additionally, by optimizing the λ/4 phase‐shift position and the duty cycle of gratings, the output power at the front‐end of the 4‐wavelength laser is significantly improved. Specifically, the ratio of the output power from the front‐end and rear‐end of the laser increases from the conventional 1.00 to 2.51. This work provides a competitive candidate for multi‐wavelength, high‐performance, and large‐scale silicon‐based light sources used in data centers, lidar, and component detection.

Mechanisms of multi-layered Rayleigh noise in Brillouin optical correlation-domain reflectometry

In Brillouin optical correlation-domain reflectometry (BOCDR), sinusoidal modulation is applied to the output frequency of a light source, with spatial resolution inversely related to the modulation amplitude. We have developed an effective method to estimate the modulation amplitude using the width of the noise spectrum caused by Rayleigh scattering, eliminating the need for an optical spectrum analyzer or modifications to existing equipment. However, the Rayleigh noise spectrum often displays a three-layered structure, complicating the identification of the appropriate spectral components for estimating the modulation amplitude. In this work, we investigate the origins of this three-layered Rayleigh noise spectrum and identify the directivity of an optical circulator as the source of the third noise component. As replacing the circulator with alternative optical components is not easy, it remains an essential part of the system. Our analysis shows that the third noise component exhibits significantly small variation in spectral width with changes in modulation frequency compared to the first and second components. This characteristic allows for the effective separation and identification of the third noise component, thereby enhancing the accuracy and convenience of modulation amplitude estimation in BOCDR.

Non-destructive detection of fructose solutions via Terahertz spectroscopy enhanced by Frequency Selective Surface (FSS)

Terahertz (THz) spectroscopy, combined with Frequency Selective Surfaces (FSS), is emerging as a powerful non-destructive technique for detecting and analysing the properties of biological samples. In this study, we explored the use of THz spectroscopy for detecting fructose solutions with concentrations ranging from 0.2 % to 10 %. Using femtosecond laser light sources, the THz transmission and absorption characteristics of fructose were investigated. The integration of FSS significantly enhanced the sensitivity of THz detection, yielding a 16 % improvement at 1.29 THz and 28 % at 1.67 THz. UV–Vis and Fourier Transform Infrared (FTIR) spectroscopy were employed to compare results with traditional methods, highlighting the superior sensitivity of THz spectroscopy, especially at low concentrations. The findings suggest that THz spectroscopy, enhanced by FSS, has strong potential for advancing non-invasive testing in biological and environmental applications.

Demonstration of potential DNA contamination introduced by laboratory consumables using Fluorescein

The development of increasingly efficient DNA extraction and profiling kits has increased the amount of allelic information obtained from trace DNA samples, but also inadvertently, increased the detection of DNA contamination. This study aimed to evaluate the potential of DNA transfer using fluorescein, fluorescent under an alternate light source, in the use of a range of forensically relevant DNA profiling consumables. An evaluation of two pre-lysis methods adopting three different sample tubes, some with deliberate seal damage, showed the PrepFiler™ Automated Forensic DNA Extraction Kit caused leakage and crusting when the rim of the PrepFiler™ LySep column was compromised, but no leakage was observed under the same conditions using the Investigator STAR Lyse&Prep kit. The AutoLys tube showed minimal leakage using the PrepFiler™ chemistry. A DNA extract tube with an external thread, similar to the AutoLys tube, showed no leakage after fridge or freezer storage. However, it highlighted that a centrifugal spin does not guarantee all the DNA will pool at the base of the tube. A comparison of adhesive plate sealing films to 8-well strip caps for sealing 96-well PCR plates showed the adhesive plate sealing films presented a lower risk of DNA transfer, largely due to the adhesion of dispersed liquid on the sticky surface of the film. Overall, this study highlighted a number of variables that may be considered in the development of more refined contamination minimisation protocols in respect to increased sensitivities of DNA profiling.

Estimation of nighttime PM2.5 concentrations over Seoul using Suomi NPP/VIIRS Day/Night Band

With rapid economic development and urban growth, Seoul experiences severe air pollution due to fine particulate matter with an aerodynamic diameter of ≤2.5 μm (PM2.5), which is detrimental to human health. Although recent studies have extensively focused on estimating daytime PM2.5 concentrations using various types of satellite data, there remains a significant lack of research on nighttime PM2.5 estimations. This study estimated nighttime PM2.5 in Seoul from December 2018 to November 2019 using multiple linear regression (MLR) and random forest (RF) models. These models, which incorporated data on radiance, moon illumination fraction, and terrain height from the Visible Infrared Imaging Radiometer Suite (VIIRS) Day/Night Band (DNB) on board the Suomi National Polar-orbiting Partnership satellite covering all moon phases, also utilized meteorological data from the ERA5 reanalysis by the European Centre for Medium-Range Weather Forecasts (ECMWF). To address multicollinearity, seasonal models were developed using forward stepwise regression and variance inflation factor analysis. DNB radiance analysis indicates that the high intensity of artificial light sources in Seoul significantly reduces the impact of moonlight, leading to notable changes in the DNB radiation associated with PM2.5 concentrations. Consequently, this study estimated nighttime PM2.5 over Seoul across all moon phases. These estimates were then validated through 10-fold cross-validation. The RF model exhibited superior accuracy, with a coefficient of determination (R2) of 0.65–0.90, compared to MLR, with R2 of 0.15–0.50, reflecting seasonal fluctuations in the model performance. The developed models can be applied to estimate reliable nighttime PM2.5 concentrations in megacities with strong artificial light sources, utilizing a comprehensive dataset from satellite observations for all moon phases. Additionally, our findings can serve as scientific data for establishing environmental policies by providing valuable insights into understanding air pollution primarily caused by PM2.5.

Red-shift of the photoluminescent emission and enhancement of the internal quantum efficiency by co-doping Gd3+ in Tb3Al5O12: Ce3+ phosphors for warm WLEDs

White Light Emitting Diodes (WLEDs) are widely used in our lives as the fourth generation of solid-state lighting sources. However, the phosphors in the WLEDs device lack a red component, resulting in a cool white light, which affects the quality of lighting while damaging the user's eyesight. In this work, the Tb3Al5O12: Ce3+ (TAG: Ce3+) and Tb3Al5O12: Ce3+, Gd3+ (TAG: Ce3+, Gd3+) phosphors were synthesized by sol-gel method. Powder X-ray diffraction analysis confirmed the successful substitution of Ce3+ and Gd3+ in the system, as evidenced by the quantifiable expansion of the unit cell volume when Tb3+ was replaced with Ce3+ and Gd3+. As the increasing of Gd3+ doping concentration in the TAG: 0.025Ce3+, yGd3+ phosphors, the emission peak of Ce3+ (arises from the 5d→4f transition) shifted from 565 nm to 580 nm. The photoluminescence emission intensity of TAG: 0.025Ce3+, 0.6Gd3+ phosphor can be increased by about 192 % compared to TAG: 0.025Ce3+ phosphor (y = 0). The Gd3+-to-Ce3+ energy transfer is robustly supported by the prolonged lifetime of Ce3+ with an increase in Gd3+ content in TAG: 0.025Ce3+, yGd3+. Notably, the energy transfer process from Gd3+ to Ce3+ effectively enhanced the internal quantum efficiency (IQE) of the TAG: 0.025Ce3+, yGd3+ phosphors, up to 70.14 %. Variable-temperature emission spectra indicates that TAG: Ce3+, Gd3+ phosphors prepared by the sol-gel method have excellent luminescent thermal stability. Ultimately, the WLEDs devices assembled with TAG: Ce3+, Gd3+ phosphors can produce warm white light, which indicates that TAG: Ce3+, Gd3+ phosphors are a potential material for warm WLEDs.

Single-image SVBRDF estimation with auto-adaptive high-frequency feature extraction

In this paper, we address the task of estimating spatially-varying bi-directional reflectance distribution functions (SVBRDF) of a near-planar surface from a single flash-lit image. Disentangling SVBRDF from the material appearance by deep learning has proven a formidable challenge. This difficulty is particularly pronounced when dealing with images lit by a point light source because the uneven distribution of irradiance in the scene interacts with the surface, leading to significant global luminance variations across the image. These variations may be overemphasized by the network and wrongly baked into the material property space. To tackle this issue, we propose a high-frequency path that contains an auto-adaptive subband “knob”. This path aims to extract crucial image textures and details while eliminating global luminance variations present in the original image. Furthermore, recognizing that color information is ignored in this path, we design a two-path strategy to jointly estimate material reflectance from both the high-frequency path and the original image. Extensive experiments on a substantial dataset have confirmed the effectiveness of our method. Our method outperforms state-of-the-art methods across a wide range of materials.

Innovative methods for trackability and identification improvement of small objects for space traffic management

Technology solutions and operational implications need a evaluation for their crucial role in tracking and identification methodologies. The growth of objects in Earth orbit have made it more important that every space system can be accounted for to be able manage the collision risk between all space objects. Tracking and identification are intimately related as enhanced tracking capabilities minimizes the need for special identification techniques. For both features, the difference between active and passive systems are discussed. Tracking is primarily optical or radar; which of these that is being used drives the most operationally-relevant identification solutions. For example, radar tags can be made to be respond to the radio frequency (RF) energy from the radar and laser reflectors can be completely passive. Whereas identification aids for use by optical tracking are active light sources (of some selected frequency) requiring a power source.

Optical Design Study with Uniform Field of View Regardless of Sensor Size for Terahertz System Applications

The focal length in a typical optical system changes with the angle of view, according to the size of the sensor. This study proposed an optical terahertz (THz) system application where the focal length changed while the angle of view was fixed; thus, the image height was variable and responded to various sensor sizes. Therefore, it is possible to respond to various sensors with one optical system when the inspection distance is fixed. The fundamental optical system was designed by arranging the refractive power, which was determined according to the sensor size using the Gaussian bracketing method. A zoom optical system that changed the image height by fixing the angle of view and changed the focal length by moving the internal lens group was designed. THz waves exhibit minimal change in the refractive index depending on the wavelength. Moreover, their long-wavelength characteristics facilitate the development of millimeter-level pixel sizes. Therefore, the root mean square size of the maximum spot was 0.329 mm, which corrected the aberration to less than 1 mm (smaller than the pixel size). Further, a lighting analysis at 3 and 6 m locations confirmed the expansion of the lighting area by the magnification of the sensor size. After turning off certain light sources, we checked the contrast ratio via lighting analysis and confirmed that the size of one pixel was clearly distinguishable. Consequently, this newly designed optical system performed appropriately as an optical inspection system for THz system applications.