Light Source Research Articles

Beamtimes and knowledge production times: how big-science research infrastructures shape nations’ domestic and international science production

Frontier scientific discoveries increasingly rely on big-science research infrastructures, such as supercolliders, synchrotron light sources, and space telescopes, whose construction and operation involve intensive international collaboration. This collaborative nature, however, presents a challenge in balancing national interests with the common good, particularly given the substantial fiscal investments involved. This study investigates the effects of one of China’s prominent big-science infrastructures, the Shanghai Synchrotron Radiation Facility (SSRF), on the country’s production of science, differentiating between national and international scientific endeavors. Employing a rigorous difference-in-differences (DID) methodology, it evaluates SSRF’s effects on discipline-level production of publications by domestic researchers and those involving international collaboration. The empirical findings reveal compelling evidence that SSRF has significantly enhanced the production of high-impact national and international publications for disciplines reliant on the facility for experiments, particularly increasing the percentage of high-impact national publications. The findings also underscore the dual role of big-science infrastructures in fostering international research collaboration while simultaneously enhancing nations’ domestic scientific development and competitiveness. Additionally, the study provides valuable insights for research assessment and science policy discussions.

An integrated portable system for laser speckle contrast imaging and digital holographic microscopy

A multimodal quantitative phase imaging platform combining digital holographic microscopy (DHM) with laser speckle contrast imaging (LSCI) is demonstrated for imaging weakly scattering and transparent samples in a label-free manner. It uses the principle of coherence of the light source for interferometric detection of phase of transparent and semi-transparent samples. The speckle formation resulting from the coherence property of the laser source is used to track dynamic activities in the regions of interest in the sample. Integration of these two techniques onto a microfluidic chip leads to an optofluidic real-time microscope for live cell imaging applications. In this work, we have developed an integrated multimodal system combining digital holographic microscopy and laser speckle contrast imaging system for Optofluidics and in vitro studies. The sample flowing through the microfluidic channel is imaged to record holograms and video of intensity images at the same time. This enables to map the flow within a microfluidic channel and quantify the channel as well as the particle flow through the channel. The channel morphology along with the particles flowing through the channel are quantified using DHM. The two-dimensional speckle contrast images map the flow of the dynamic microbeads and cells with very high contrast in almost real time. A low-cost portable multimodal quantitative phase microscope combining DHM and LSCI has been demonstrated for real time imaging with applications in optofluidics.

Adaptation of Object Detection Algorithms for Road Indicator Lights in Complex Scenes

In the realm of autonomous driving, practical driving scenarios are fraught with numerous complexities, including inclement weather conditions, nighttime blurriness, and ambient light sources that significantly hinder drivers’ ability to discern road indicators. Furthermore, the dynamic nature of road indicators, which are constantly evolving, poses additional challenges for computer vision-based detection systems. To address these issues, this paper introduces a road indicator light detection model, leveraging the advanced capabilities of YOLOv8. We have ingeniously integrated the robust backbone of YOLOv8 with four distinct attention mechanism modules—Convolutional Block Attention Module (CBAM), Efficient Channel Attention (ECA), Shuffle Attention (SA), and Global Attention Mechanism (GAM)—to significantly enhance the model performance in capturing nuanced features of road indicators and boosting the accuracy of detecting minute objects. Additionally, we employ the Asymptotic Feature Pyramid Network (AFPN) strategy, which optimizes the fusion of features across different scales, ensuring not only an enhanced performance but also maintaining real-time capability. These innovative attention modules empower the model by recalibrating the significance of both channel and spatial dimensions within the feature maps, enabling it to hone in on the most pertinent object characteristics. To tackle the challenges posed by samples rich in small, occluded, background-similar objects, and those that are inherently difficult to recognize, we have incorporated the Focaler-IOU loss function. This loss function deftly reduces the contribution of easily detectable samples to the overall loss, thereby intensifying the focus on challenging samples. This strategic balancing of hard-to-detect versus easy-to-detect samples effectively elevates the model’s detection performance. Experimental evaluations conducted on both a public traffic signal dataset and a proprietary headlight dataset have yielded impressive results, with both mAP50 and mAP50:95 metrics experiencing significant improvements exceeding two percentage points. Notably, the enhancements observed in the headlight dataset are particularly profound, signifying a significant step forward toward realizing safer and more reliable assisted driving technologies.

Redefining artificial lighting through spectral engineering of light sources for well-being

Light-emitting diodes (LEDs) have revolutionized artificial lighting, but also exposed the detrimental health effects that stem from insufficient exposure to natural light. Human-centric artificial lighting requires both visual quality and circadian lighting performance that mimics daylight’s evolving spectral power distribution (SPD). Here, we present a color-tunable LED-based light source that achieves SPDs similar to various conditions of daylight and incandescent lighting over the range of visible wavelengths. This light source is comprised of a linear combination of light converter channels containing dyes exhibiting thermally activated delayed fluorescence (TADF) fabricated through additive manufacturing, photoexcited by violet-emitting LEDs (VLED). This hybrid light source establishes a new benchmark for state-of-the-art artificial lighting at approximating daylight, with Illuminating Engineering Society (IES) color gamut index Rg values within 3%, IES color fidelity index Rf values within 7% through CCT values ranging from 4277 K to 22,333 K. We propose efficiency metrics to accurately quantify similarity between light sources and the respective reference daylight spectrum encompassing visual and circadian effects, facilitating WLED benchmarking. The efficiency metrics pertaining to circadian lighting performance remain within 10% over the same CCT range. These results advance lighting science to address simultaneously the grand challenges of health and sustainability.

Photodamage prediction model and optimal lighting system for polychrome artworks in museum

When lighting polychrome artworks in museum, the light sources are required not only to provide high-quality visual performance, but also to minimize the photodamage. Currently, though there are mature methods to calculate visual performance, how to predict the degree of photodamage remains a challenge, which leads to a lack of light sources satisfying both visual and protection requirements. Our study conducted a series of 294 accelerated aging experiments spanning over 11 years for materials commonly used in Chinese polychrome artworks, using isoenergetic white-light D55 and 10 different wavelengths of narrow-band light as experimental light sources. The mathematical model predicting the photodamage degree caused by intensity (I), exposure time (t), the relative spectral power distribution of the light source (S(λ)), and the irradiated material's relative spectral responsivity (P(λ)) to polychrome artworks was established, and the mean absolute percentage error of the model, as verified by experiments, was 11.63 %. Combined with the existing visual performance calculation methods, an optimal lighting algorithm that simultaneously meets high-quality visual performance and minimum photodamage was developed, followed by developing a new Spectrally Tunable White LEDs (STWLEDs) lighting system with 10 LED chips. It is found that the STWLEDs can adjust and output the optimal spectra and recommended illuminance according to the characteristics of polychrome artworks, thus realizing lighting with minimum photodamage, meanwhile, satisfying high-quality visual performance. After testing, as well as satisfying the requirements of visual performance, the average photodamage is reduced by 40.95 % with STWLEDs compared with the traditional WLEDs.

Characterizing novel Indium Phosphide pad detectors with focused X-ray beams and laboratory tests

Future tracking systems in High Energy Physics experiments will require large instrumented areas with low radiation length. Crystalline silicon sensors have been used in tracking systems for decades, but are difficult to manufacture and costly to produce for large areas. We are exploring alternative sensor materials that are amenable to fast fabrication techniques used for thin film devices. Indium Phosphide pad sensors were fabricated at Argonne National Lab using commercially available InP:Fe 2-inch mono-crystal substrates. Current-voltage and capacitance-voltage characterizations were performed to study the basic operating characteristics of a group of sensors. Micro-focused X-ray beams at Canadian Light Source and Diamond Light Source were used to study the response to ionizing radiation, and characterize the uniformity of the response for several devices. Electrical test results showed a high degree of performance uniformity between the 48 tested devices. X-ray test beam results showed good performance uniformity within tested devices after accounting for spatially-local defects and edge fields. This motivates further studies into thin film devices for future tracking detectors.

The interplay of irradiated- and shaded zones in photoreactor scale-up

Photochemical processes enable highly-selective synthesis routes under mild reaction conditions. Yet, photoreactions are seldom implemented on industrial scale. One of the main challenges is the exponential light attenuation with increasing optical depth. As a result, few photons are available at positions far from the light source, leading to shaded zones of low reactivity. To study the effect of shaded zones, a compartment photoreactor model is presented and used for optimization of the reaction conditions, in particular during scale-up. Using photooxidation in a Taylor-flow capillary reactor as a benchmark case, the photosensitizer concentration, the light intensity and liquid mixing are identified as the key parameters for the formation and impact of shaded zones on reactor performance. It is shown that shading reduces the conversion already on lab-scale by up to 13% for operating conditions with high photosensitizer concentration and light intensity. In an upscaled reactor, intensified liquid mixing leads to an up to 4.3-fold increase in conversion

Broadband generation and tomography of non-Gaussian states for ultra-fast optical quantum processors

Quantum information processors benefit from high clock frequencies to fully harness quantum advantages before they are lost to decoherence. All-optical systems offer unique benefits due to their inherent 100-THz carrier frequency, enabling the development of THz-clock frequency processors. However, the bandwidth of quantum light sources and measurement devices has been limited to the MHz range, with nonclassical state generation rates in the kHz range. In this study, we demonstrated broadband generation and quantum tomography of non-Gaussian states using an optical parametric amplifier (OPA) as a squeezed light source and an optical phase-sensitive amplifier (PSA). Our system includes a 6-THz squeezed-light source, a 6-THz PSA, and a 66-GHz homodyne detector. We successfully generated non-Gaussian states at a 0.9 MHz rate with sub-nanosecond wave packets using a continuous-wave laser. The performance is currently limited by the jitter of superconducting detectors, restricting the usable bandwidth to 1 GHz. Our technique extends the bandwidth to GHz, potentially increasing non-Gaussian state generation rates for practical optical quantum processors using OPAs.

The design of high-brightness ERL-FEL injector based on VHF electron gun

In the past decade, the fourth-generation light source based on the combination of Energy Recovery Linac (ERL) and Free-Electron Laser (FEL) using superconducting linear accelerators has garnered significant attention. It holds immense potential, particularly in generating high-power Extreme Ultraviolet (EUV) light sources. This article primarily focuses on the physical design of an injector for ERL-FEL, based on a Very High Frequency (VHF) electron gun with a charge of 100 pC. The beam energy is accelerated to 10 MeV using 3-cell superconducting cryomodule. The optimization of beam parameters is conducted through employment of BMad and ASTRA simulations, incorporating the concept of Merger optimization. The beam emittance is less than 0.6 mm mrad, and the peak current at the injector exit exceeds 18 A. We present a new method to evaluate the Longitudinal Space Charge (LSC) effects in merger sections, which can be readily applied in design work. Furthermore, we introduce a novel type of merger. The performance of this new merger is comparable to the previously known optimum, the zigzag merger, offering a potential alternative solution for injectors in ERLs.

Light-emitting diode-based absorbance detectors for flow-through analysis in analytical chemistry: A tutorial

The development of light-emitting diodes (LEDs) has played a significant role supporting many recent advances made in chemical analysis. Their small size, low power consumption, and semi-monochromaticity make them ideal light sources for portable photometric devices used in field and on-site analysis, environmental monitoring, and industrial applications, such as process analytical technology (PAT) and continuous real-time analysis. This tutorial provides an overview and critical comparison of the key components in LED-based absorbance detectors, including light sources, optical fibres, flow cells, and photodetectors. Fundamental aspects of LEDs relating to their use in such simple detectors are discussed in detail, along with the development of multi-wavelength detectors that incorporate multiple LEDs. The tutorial also details the different methodologies for assessing and characterising the LED-based absorbance detectors. Finally, this tutorial presents some selected applications of LED based photometric detectors in gas sensing, flow injection analysis (FIA), and coupled with separation techniques such as ion chromatography, liquid chromatography, and capillary zone electrophoresis (CZE).

Highly Sensitive Perovskite Photoplethysmography Sensor for Blood Glucose Sensing Using Machine Learning Techniques.

Accurate non-invasive monitoring of blood glucose (BG) is a challenging issue in the therapy of diabetes. Here near-infrared (NIR) photoplethysmography (PPG) sensor based on a vapor-deposited mixed tin-lead hybrid perovskite photodetector is developed. The device shows a high detectivity of 5.32×1012 Jones and a large linear dynamic range (LDR) of 204 dB under NIR light, guaranteeing accurate extraction of eleven features from the PPG signal. By a combination of machine learning, accurate prediction of blood glucose level with mean absolute relative difference (MARD) as small as 2.48% is realized. The self-powered PPG sensor also works for real-time outdoor healthcare monitors using sunlight as a light source. The potential for early diabetes diagnoses by the perovskite PPG sensor is demonstrated.

Thermal reflectance of fabric in color temperature spectral domain

PurposeThis study aims to explore the thermal reflectance of fabrics under sunlight or other thermal radiation sources at various color temperatures.Design/methodology/approachThis study analyzed the spectral distribution of sunlight at different solar altitude angles as well as the spectral distribution characteristics of other light and thermal radiation sources, pointing out that their color temperatures can be used to identify their spectral distribution domains. Reflectance, transmittance, absorptance and color temperature domain reflectance of 35 different fibers and color fabrics were tested in a wide spectral range. The different behavior of these optical parameters in the segmented spectrum is discussed. The temperature rise tests demonstrate that the reflectance corresponding to the color temperature of the radiation sources is highly correlated with the temperature rise results.FindingsThe reflectance in the color temperature domain shows a strong correlation with the radiation source at same color temperature. The correlation coefficients for the 6,000 K xenon lamp test are −0.96 and −0.90 in two groups, and for the 3,200 K tungsten iodine lamp test are −0.87 and −0.90 as well.Originality/valueThe concept of fabric thermal reflectance in the color temperature domain was first introduced to match different thermal radiation sources. Validation of temperature rise is conducted through a self-constructed tester with unidirectional adiabatic heating. This new discovery could serve as a basis for developing functional fabric or clothing, such as sun-proof clothing, fire protection clothing, etc.

Incandescent metasurfaces: A tutorial

Incandescence has long been the most popular source of light, despite a number of limitations in terms of efficiency, polarization, and coherence. In the last twenty years, it has been shown that most of these limitations can be overcome by taking advantage of the advances in nanophotonics. In this paper, we provide a tutorial presentation of the field with emphasis on the fundamental principles used to control the properties of thermal radiation in the far field. We introduce several figures of merit and list some directions for future work.

Development of wavelength dispersion measurement method using Fresnel reflection of fiber under test at both end faces

The phase shift method is generally used for wavelength (chromatic) dispersion measurement of optical fibers. However, the phase shift method requires a long fiber under test (FUT) of several hundred meters or more to obtain high temporal resolution. Therefore, measuring specialty fibers with short production lengths and amplification fibers that absorb light at specific wavelengths used for fiber lasers is difficult with this method. We have developed a method to measure the beat spectrum, by incident, an incoherent tunable light source (I-TLS) composed of amplified spontaneous emission (ASE) to a FUT. The FUT constitutes a Fabry–Perot resonator using Fresnel reflections at both end faces of the fiber. Chromatic dispersion can be calculated from the wavelength dependence of the refractive indices of the FUT, enabling measurement with short fiber lengths. The standard deviation of the chromatic dispersion @1550 nm was 0.352 ps/(nm km) based on five measurements of a FUT of approximately 3 m. The error between the manufacturer's measurement of chromatic dispersion @1550 nm, and the average value measured in this study was measured at 0.56%, indicating that it can be measured with very high accuracy.

Survivability and life support in sealed mini-ecosystems with simulated planetary soils

Establishing a sustainable life-support system for space exploration is a formidable challenge due to the vast distances, high costs, and environmental differences from Earth. Building upon the lessons from the Biosphere 2 experiment, we introduce the novel “Ecosphere” and “Biosealed” systems, self-sustaining ecosystems within customizable, enclosed containers. These systems incorporate terrestrial ecosystems and groundwater layers, offering a potential model for transplanting Earth-like biomes to extraterrestrial environments. Over 4 years, we conducted rigorous experiments and analyses to understand the dynamics of these enclosed ecosystems. We successfully mitigated moisture deficiency, a major obstacle to plant growth, by incorporating groundwater layers. Additionally, we quantified microbial communities proliferating in specific soils, including simulated lunar and Ryugu asteroid regolith, enhance plant cultivation in space environments. Metagenomic analysis of these simulated space soils revealed diverse microbial populations and their crucial role in plant growth and ecosystem stability. Notably, we identified symbiotic relationships between plants and Cyanobacteria, enhancing oxygen production, and demonstrated the potential of LED lighting as an alternative light source for plant cultivation in sun-limited space missions. We also confirmed the survival of fruit flies within these systems, relying on plant-produced oxygen and photosynthetic bacteria. Our research provides a comprehensive framework for developing future space life-support systems. The novelty of our work lies in the unique design of our enclosed ecosystems, incorporating groundwater layers and simulated extraterrestrial soils, and the detailed analysis of microbial communities within these systems. These findings offer valuable insights into the challenges and potential solutions for establishing sustainable human habitats in space, including the importance of microbial management and potential health concerns related to microbial exposure.

All-fiber supercontinuum absorption spectroscopy for mid-infrared gas sensing

The development of compact fiber-based light sources emitting over a wide wavelength range in the mid-infrared and their application to the detection of greenhouse gases and volatile organic compounds still remain of critical interest. In the present work, we make use of several dedicated infrared fibers for implementing a mid-infrared optical device pumped by a thulium doped-fiber laser around 1.965 μm that simultaneously enables a first nonlinear stage of frequency conversion and supercontinuum generation and a second linear stage of gas absorption spectroscopy. As a proof-of-principle, we carry out mid-infrared supercontinuum absorption spectroscopy of methane around 7.7 μm by means of a hollow-core fiber-based gas cell combined to a commercial Fourier-transform infrared spectrometer. Our all-fiber configuration operating in the femtosecond regime at megahertz repetition rate allows the detection of methane concentrations as low as 20 ppm.

A Cr3+-triggered near-infrared tungstate phosphor for organic compound non-destructive detection

Cr3+-doped near-infrared (NIR) luminescent materials have become a research hotspot in luminescence functional materials. However, developing NIR phosphors with emission wavelengths exceeding 1000 nm, suitable for organic compound non-destructive analysis, remains a significant challenge. In this study, LiSc(WO4)2:Cr3+ NIR phosphors were synthesized using a simple solid-state reaction method. Low temperature photoluminescence emission spectrum, electron paramagnetic resonance spectrum, and fluorescence decay curve confirmed that Cr3+ ions occupied both LiO6 and ScO6 octahedron sites, forming two luminescence centers. The sample exhibited an emission wavelength of 1082 nm under 523 nm excitation, with a full width at half maximum (FWHM) of 290 nm. As the Cr3+ concentration increased, the emission peak showed a blue shift. The sample LiSc(WO4)2:0.3Cr3+ with optimal optical performance exhibited an emission wavelength of 1023 nm and an FWHM of 228 nm. Its luminescence intensity retained 38.4% of room temperature value at 380 K, and the internal and external quantum efficiency were 33.2% and 18.9%, respectively. When packaged with a 525 nm green LED, the device as a NIR light source is capable of accurately identifying water, ethanol, ammonia, and silicone oil. This work demonstrates that tungstate materials have great potential in the field of optical materials and offers a new perspective for selecting matrix materials in the development of Cr3+-doped long-wavelength broadband NIR phosphors.

A proposal for cut marks classification using machine learning: Serrated vs. non-serrated, single vs. double-beveled knives.

In tool mark identification, there is still a lack of characteristics and methodologies standardization used to analyze and describe sharp force trauma marks on skeletal remains. This study presents a classification method for cut marks on human bones, providing an applicable methodology for their examination and the relevant terminology for describing cases of sharp force trauma. A total of 350 cut marks were produced by stabbing pig ribs (Sus scrofa) with seven knives. The samples were analyzed under a stereomicroscope with a tangential light source. Through the analysis of cut marks, eleven traits were identified as significantly associated with the type of knife used. These traits included the general morphology of the kerf shape, the entrance and exit cross-profile shapes, the location of the rising on the entrance and exit cross-profile, the presence or absence of feathering, the presence or absence of shards and the location and the general morphology of the mounding. Binary logistic regression models were later trained and tested using nine out of the eleven traits. The first model categorized the cut mark as either produced by a serrated or non-serrated blade, while the second, as either produced by a single- or double-beveled blade. Classification scores of those models ranged between 63%-85% for the serration class and 63%-89% for the blade bevel class. This study proposes a new set of traits and the use of machine learning models to standardize and facilitate the analysis of stab wounds.

An enzyme-fused phycobiliprotein synthesis system developed for visual whole-cell biosensors for the detection of cadmium during wastewater treatment

Transcription factor-based whole-cell biosensors are simple and inexpensive tools for monitoring heavy metals during environmental processes. However, most biosensors are depend on instrumentation or have low sensitivity. Here, all the enzymes in the phycobiliprotein synthesis system were fused with the phycocyanin apoprotein to create a system to synthesize enzyme-fused phycobiliproteins with comparable fluorescence. We replaced the biliprotein synthesis system T7 promoter with cadmium-sensing genetic elements to create two visual cadmium biosensors (Epcad-cbsA and Epcad-cbsS). Cd2+ was detected at nanomolar concentrations by measuring the fluorescence intensity and evaluating the degree of color change of the cell pellets. Moreover, good linear correlations were observed with Cd2+ concentrations up to 250 nM. Compared with cellular fluorescence, our cadmium biosensor is more sensitive when cell color is used as the output signal, with detection limits of 7.6 nM for Epcad-cbsA and 3.2 nM for Epcad-cbsS. This visual platform was validated by assessing bioavailable cadmium during wastewater treatment. By immobilizing large amounts of phycobilin with the proteins in cells, our designed biosensors do not require pigment extraction or specialized light sources or detection devices. This work demonstrates that a biliprotein synthesis system can be a novel platform for the development of simple, low-cost, and highly sensitive visual biosensors for real-world applications.

Influence of Exposure Distance on Light Irradiance of Dental Curing Lamps in Various Operating Modes

The efficiency of photopolymerisation significantly impacts achieving a high degree of conversion and, consequently, determines the success and strength of resin-based composite (RBC) restorations. The study aimed to measure the light irradiance of selected LED curing lamps, taking into account various exposure modes and the increased distance of the light source from the radiometer surface. The study material consisted of 21 LED polymerisation lamps of a single type (Woodpecker Medical Instrument Co., Guilin, China) with three exposure modes: standard, soft start, and pulse. During the measurement, the distance was increased from 0 mm to 8 mm, every 2 mm. Light irradiance measurements were made with a Bluephase Meter II photometer (Ivoclar Vivadent, Opfikon, Switzerland). Increasing the distance affected the soft mode the most, causing a significant drop in light irradiance on the photometer. Standard mode coped best with distance. Even at a distance of 0 mm, the soft start mode does not reach the power of the standard and pulse modes. The standard mode seems to be the most clinically effective, especially if it is planned to polymerise a material in a deep cavity. The soft start mode, as the least resistant to increasing distance, is recommended for use in front teeth or the cervical area.