Light Source Research Articles

The effect of supplemental LED lighting in the range of UV, blue, and red wavelengths at different ratios on the accumulation of phenolic compounds in pak choi and swiss chard

Phenolic compounds are known for their health-promoting effects on humans. Pak choi (Brassica rapa ssp. chinensis) and Swiss chard (Beta vulgaris subsp. vulgaris) are used here as model plants, as they are eaten raw as baby leaf lettuce and differ in their phenolic compound profile while showing similar morphology. In a greenhouse an artificial light source with UV-B (215 mW m−2), blue (104 μmol/m−2 s−1) and red (245 μmol/m−2 s−1) LEDs was implemented to increase phenolic compounds during the last days before harvest. Pak choi shows an increase or trend towards an increase in the monoacylated triglycosides of kaempferol and quercetin after 4 days of irradiation for 4 h each. For example kaempferol-3-caffeoyl-sophoroside-7-glucoside was increased at low PAR values in the third run and red-dominated light treatment by up to 120 %. In addition, it was observed that the red variety ‘Amur’ has higher concentrations of quercetin glycosides which were increased often. In swiss chard, on the other hand, there was only a sporadic increase in vitexin glycosides. Despite very different concentrations in some samples, 2″-glucosyl-vitexin and 2′′-glucosyl-6′′-malonyl-vitexin showed significant increases of up to 350 % in the two chard varieties Lukullus and Rhubarb chard. The results suggest that the exposure time or intensity of UV-B radiation needs to be optimized for each species and has not yet consistently led to an increase but trends in phenolic compounds and in antioxidant activity in this study.

Photoluminescence properties of Li3Sc1-x(BO3)2:xCr3+ phosphors and enhanced near-infrared emission and thermal stability by Yb3+ codoping

Cr3+ activated broadband near-infrared (NIR) emitting phosphors have attracted more attention worldwide as they are strongly expected to be promising light convertors for phosphor-converted NIR light sources for NIR spectroscopy and imaging technologies. Herein, a new broadband NIR emitting phosphor Cr3+-doped Li3Sc(BO3)2 (LSBO) is introduced. Microcrystalline powders of LSBO doped with different Cr3+ concentrations were synthesized by solid state reactions and show an NIR emission extending from 700 to 1100 nm with a peak at 830 nm upon excitation at 460 nm. The structure, concentration and temperature-dependent luminescence properties of LSBO:Cr3+ phosphors were discussed in detail. The optical properties of Cr3+ ions in LSBO were examined in terms of spectroscopic parameters. Moreover, efficient energy transfer from Cr3+ to Yb3+ is leveraged to significantly improve the NIR emission intensity and the thermal stability. The enhancement and energy transfer mechanisms have been discussed in detail. These results open up new ways to realize efficient NIR-emitting materials.

Noise Suppression Method of Fiber Optic Sensors Driven by Broadband Light Source

Noise Suppression Method of Fiber Optic Sensors Driven by Broadband Light Source

Development of a Light Source Position Estimation System for Accurate Drone Flight

Development of a Light Source Position Estimation System for Accurate Drone Flight

Biosynthesis, characterization of Ag2O nanoparticles for enhancement of antioxidant and photo degradation activities

Silver oxide (Ag2O) nanoparticles were synthesized via Biosynthesis methods using Croton macrotachyus leaf extract silver sulphate (Ag2SO4) was used as precursors and the extract was used in the reactions as reducing, stabilizing and capping agents which is a very easy and inexpensive synthesis method. Metal oxide nanoparticles characterized using UV–visible, TGA, Fourier transform infrared(FTIR),powder X-ray diffraction(XRD), X-ray photoelectron(XPS), and Scanning Electron Microscopy(SEM) with Energy Dispersive X-Ray(EDX) and Transmission Electron Microscopy(TEM), High Resolution Transmission Electron Microscope(HRTEM), and Selected Area Electron (SAED) which is used for determination of crystalline size, morphology,particle size and oxidation state with composition of elements in the sample. Metal oxide nanoparticles have a significant photo catalytic performance under visible light source confirmed that study supported Ag2O spherical structure, which exhibits enhanced photo catalytic activity and anti-oxidant activities as well as the size of the Ag2O nanoparticles was between 16 nm and 21 nm from the XRD(Scherrer equation),SEM & TEM) imaje software and Photo catalytic activity of Ag2O NPs were assessed against methylene blue (MB) dye degradation under natural sunlight illumination for 60 min. This sustainably photo degraded in direct solar irradiance with remarkable degradation percentage which is greater than 96.35 % and Scavenging activities Ag2O nanoparticles enhanced DDPH scavenging activities was 88 %

Wavelength-Dependent Dynamic Behavior in Thiol-Ene Networks Based on Disulfide Exchange.

While latent catalysts have become a well-established strategy for locally and temporally controlling bond exchange reactions in dynamic polymer networks, there is a lack of inherently tailorable systems. Herein, we introduce a thiol-ene network based on disulfide exchange that alters its dynamic properties as a function of the color of light used during the curing reaction. For this purpose, selected allyl-bearing disulfides are synthesized, which are transparent at 450 nm but undergo disulfide scission upon 365 nm light irradiation, as confirmed by UV-vis and EPR measurements. Incorporated into a thiol-ene resin, the wavelength used in the curing reaction defines the dynamic properties of the obtained photopolymer. At 450 nm, photocuring yields a dynamic network with disulfide bonds, which relaxes to 63% of its original stress within 112 s at 160 °C (without the requirement of an external catalyst). In contrast, curing with 365 nm light induces disulfide scission yielding photopolymers, which contain predominately monosulfidic links. The permanent nature of the links effectively prevents relaxation of the polymer within a reasonable period of time, confirming the successful alteration of its dynamic properties simply by the color of the light source used.

Maximum Angle of Light Source for Mobility in Visible Light Communication

Maximum Angle of Light Source for Mobility in Visible Light Communication

Simulating a Temperature, Stress And Strain FBG Sensor for Troposphere Layer

In this study, a simulation and design for a temperature (T) sensor are investigated by using the fiber Bragg gratings (FBG). The study investigated and characterized the FBG regarding maximum reflectivity, bandwidth, and the influence of applied strain on the shift in Bragg wavelength (λB). This is via measuring sensitivity of wavelength shift under strain in an optical sensing system. The response of FBG sensors was also investigated and optimized. Uniform FBG spectra and theoretical comparisons were conducted considering the influence of several selected external strain/stress (S) values: 101.325, 89.874, 79.495, 70.108, 61.640, 54.019, 47.181, 41.060, 35.599, 30.742, 26.436. The Optisystem 16 software is analyzing these two types of effects. The measured parameters, such as sensitivity, were determined by using a white light source. The light source operating wavelength was 1550 nm. This is to design the sensor especially for troposphere that have high sensitivity (1279.7472 pm/oC. The sensitivity obtained exhibited varying values between 1279.7472 and 1239.7551 for strain. The peak sensitivity observed is associated with 550 nm of wavelength. Result for measured sensitivity against S by the FBG sensor was 15.5087 pm/oC with sensor length 20 mm. While it was found equals 15.5131 pm/oC with sensor length 10 mm. T sensing is simulated for selected values (15, 8.5, 2, -4.5, -11, -17.5, -24, -30.5, -37, -43.5, -50 oC). Resulted sensitivity was found to fluctuate fitting sine, Long Normal, and Boltzmann functions, indicating large sensitivity for the simulated sensor responses.

In Situ Light-Source Delivery During 5-Aminulevulinic Acid-Guided High-Grade Glioma Resection: Spatial, Functional and Oncological Informed Surgery

Background/Objectives: 5-aminulevulinic acid (5-ALA)-guided surgery for high-grade gliomas remains a challenge in neuro-oncological surgery. Inconsistent fluorescence visualisation, subjective quantification and false negatives due to blood, haemostatic agents or optical impediments from the external light source are some of the limitations of the present technology. Methods: The preliminary results from this single-centre retrospective study are presented from the first 35 patients operated upon with the novel Nico Myriad Spectra System©. The microdebrider (Myriad) with an additional in situ light system (Spectra) can alternately provide white and blue light (405 nm) to within 15 mm of the tissue surface to enhance the morphology of the anatomical structures and the fluorescence of the pathological tissues. Results: A total of 35 patients were operated upon with this new technology. Eight patients (22.85%) underwent tubular retractor-assisted minimally invasive parafascicular surgery (tr-MIPS). The majority had high-grade gliomas (68.57%). Fluorescence was identified in 30 cases (85.71%), with residual fluorescence in 11 (36.66%). The main applications were better white–blue light alternation and visualisation during tr-MIPS, increase in the extent of resection at the border of the cavity, identification of satellite lesions in multifocal pathology, the differentiation between radionecrosis and tumour recurrence in redo surgery and the demarcation between normal ependyma versus pathological ependyma in tumours infiltrating the subventricular zone. Conclusions: This proof-of-concept study confirms that the novel in situ light-source delivery technology integrated with the usual intraoperative armamentarium provides a spatially, functionally and oncologically informed framework for glioblastoma surgery. It allows for the enhancement of the morphology of anatomical structures and the fluorescence of pathological tissues, increasing the extent of resection and, possibly, the prognosis for patients with high-grade gliomas.

Fiber Optical Sensor for Antioxidant Detection Levels in Blueberries Using Wavelength-Based LED Light Sources

Blueberries' high antioxidant content, which includes flavonoids, anthocyanins, and phenolic acids, greatly enhances their nutritional and therapeutic value. These substances are crucial targets for food quality and nutrition research because they neutralize free radicals and lower oxidative stress. However, conventional techniques for quantifying antioxidants, such as High-Performance Liquid Chromatography (HPLC), are expensive, time-consuming, and frequently needed for destructive sample preparation. This study suggests a fiber-optical sensor (FOS) system as a unique, destructive method for identifying and measuring antioxidants in blueberries. Blueberry samples are illuminated by the system using wavelength-specific LED light sources, which are guided to and from the sample via fiber optics for interaction. Using the distinctive absorption and scattering characteristics of the compounds at particular wavelengths, the reflected or transmitted light is captured by a photodetector and evaluated to calculate antioxidant amounts. This proposed system is a useful tool for the food sector because of its many benefits, which include its capacity to offer real-time analysis, portability, and adaptability to in-field applications. This paper examines the sensor's design principles, assesses how well it performs in comparison to traditional techniques, and emphasizes how useful it could be for agricultural research and quality control.

Transcranial optogenetic brain modulator for precise bimodal neuromodulation in multiple brain regions

Transcranial brain stimulation is a promising technology for safe modulation of brain function without invasive procedures. Recent advances in transcranial optogenetic techniques with external light sources, using upconversion particles and highly sensitive opsins, have shown promise for precise neuromodulation with improved spatial resolution in deeper brain regions. However, these methods have not yet been used to selectively excite or inhibit specific neural populations in multiple brain regions. In this study, we created a wireless transcranial optogenetic brain modulator that combines highly sensitive opsins and upconversion particles and allows for precise bimodal neuromodulation of multiple brain regions without optical crosstalk. We demonstrate the feasibility of our approach in freely behaving mice. Furthermore, we demonstrate its usefulness in studies of complex behaviors and brain dysfunction by controlling extorting behavior in mice in food competition tests and alleviating the symptoms of Parkinson’s disease. Our approach has potential applications in the study of neural circuits and development of treatments for various brain disorders.

A single nanophotonic platform for producing circularly polarized white light from non-chiral emitters

Direct manipulation of light spin-angular momentum is desired in optoelectronic applications such as, displays, telecommunications, or imaging. Generating polarized light from luminophores avoids using optical components that cause brightness losses and hamper on-chip integration of light sources. Endowing chirality to achiral emitters for direct generation of polarized light benefits from existing materials and can be achieved by chiral nanophotonics. However, most chiral nanostructures operate in narrow wavelength ranges and involve nanofabrication processes incompatible with high-throughput production. Here, a single nanophotonic architecture is designed to sustain chiroptical resonances along the visible spectrum. This platform, fabricated with scalable soft-nanoimprint lithography transfers its chirality to conventional emitters (CdSe/CdS nanoplatelets, CdSe/CdS quantum dots, CsPbBr3, CsPbI3 perovskite nanocrystals and F8BT) placed atop, achieving a high dissymmetry emission factor (glum > 1). The dynamics study suggests enhanced out-coupling efficiency for one helicity by the photonic structure. Finally, a white light-emitting blend containing different emitters shows simultaneous dissymmetric emission values along the visible spectrum with this chiral nanophotonic platform.

Optical fiber membrane-based Fabry–Perot tactile force sensing platform powered by LED ambient lighting

This study introduces an optical fiber tactile force sensing platform powered by ambient LED lighting. Based on the interaction between a multimode optical fiber and a micro-polymer membrane, it is possible to excite an Extrinsic Fabry-Perot Interferometer (EFPI); this EFPI is pumped by collected incident light from the ambient LED lighting environment; here, a Fresnel lens and multimode fiber collect this light. The collector system maintains suitable light intensity even during 360° rotation. When transversal loads between 0 to 1 N are applied over the membrane, the tactile force sensor shows a wavelength shift towards shorter wavelengths; consequently, a 6.5 nm/N sensitivity and resolution of 0.15 N are obtained. Moreover, the phase analysis of the Fourier spectrum addresses intensity variations during rotation, revealing a sensitivity of 3 rad/N. The sensor offers stability, minimal hysteresis, minimal temperature modulation, and suitable time response across four sensing areas. Moreover, the statistical analysis and tactile force sensor performance ensure reliable tactile measurement with a null probability of overlap upon force application. It is crucial to note that this tactile force sensor provides a genuinely low-cost implementation due to the utilization of ambient LED lighting as the light source. This aspect represents an exciting advancement in fiber sensing technology.

Mechanical, permeability, and optical properties of concrete integrating light-transmitting materials with high contents and large diameters

ABSTRACT The present study focuses on developing LTC panels with high light transmission efficiency by integrating optical fibers or Polymethyl Methacrylate (PMMA) rods at volumes of 10–30% into the concrete. This aims to enhance the percentage of light intensity transmitted through the LTC to approximately 30% from the light source, a significant improvement compared to most previous studies where it was below 10%. Various configurations of these materials, differing in diameter and volume, were tested for their effects on mechanical strength, permeability, and optical properties. Unlike most previous studies using optical fibers smaller than 2.0 mm, the findings indicate that using optical fibers or PMMA rods with larger diameters improves the feasibility of casting LTC panels with ultra-high light transmission capacity and compressive strength above 40 MPa. The mechanical strength of LTC samples can be predicted based on the effective cross-section, excluding the area occupied by light-transmitting materials. The study also reveals that larger PMMA rods increase permeability due to weaker bonds with the surrounding concrete. Additionally, LTC panels can transmit colors and images without altering the original light source color, highlighting LTC’s potential for creative applications, such as smart traffic signal displays on pavements or unique architectural designs.

Recent Development of Fourier Domain Mode-Locked Laser

Since the advent of Fourier Domain Mode-Locked (FDML) lasers, they have demonstrated outstanding performance in several fields. They achieve high-speed, narrow-linewidth laser output with the new mode-locking mechanism, which has been intensively researched in the past decades. Compared with conventional wavelength-scanning light sources, FDML lasers have successfully increased the scanning rate of frequency-sweeping lasers from kHz to MHz. They are widely used in optical coherence tomography, spectral analysis, microscopy, and microwave photonics. With the deepening research on FDML lasers, several performance metrics have been optimized and improved, offering superior performance for FDML laser-based applications. This paper reviews the principles and key performance indicators of FDML lasers, as well as the recent progress made in some important applications, and highlights further research directions for FDML lasers in the future.

A bi-directional metamaterial perfect absorber based on gold grating and TiO2-InAs normal hexagonal pattern film

We present and study a bidirectional metamaterial-perfect absorber based on TiO2-InAs regular hexagonal pattern thin films and gold grating. We employ the finite difference time domain approach for simulation. Multi-narrowband perfect absorption and ultra-wideband perfect absorption can alternate as the light source's direction changes. Four narrow-band absorption peaks developed at 987 nm, 1188 nm, 1510 nm, and 2091 nm, respectively, when the incident light struck the bottom. The corresponding absorption efficiencies were 99.69 %, 99.41 %, 98.54 %, and 98.97 %. The broadband region displays the properties of perfect absorption when incident light strikes the top. It should be noted that it is not affected by the polarization or angle of the incidence. With an average absorption efficiency of 96.02 %, the structure attains over 90 % absorption in the 3023 nm range (424–3447 nm). Second, the weighted absorption efficiency of the full spectrum is as high as 96.84 %, and the AM 1.5 solar radiation spectrum and the solar absorption spectrum are strongly coincident. Furthermore, the computation results show that the thermal radiation efficiency is greater than 95 % between 300 K and 1500 K. The electric field distribution revealed that the Fabry-Perot cavity resonance within the film, the surface plasmon resonance (SPR) on the surface of the InAs and TiO2 regular hexagonal pattern films, the interstitial mode excitation between the films, and the excitation cavity coupling between cells of each unit were primarily responsible for the perfect absorption of broadband. The high-order resonant coupling in the FP cavity and the strong coupling between the local surface plasmon resonance and the FP cavity resonance in the metal grating's slit are the primary causes of the narrow band's perfect absorption. The suggested bidirectional metamaterial perfect absorber has significant promise for use in the disciplines of sensing, solar energy absorption, photoelectric detection, and photothermal conversion, as evidenced by its superb absorption and thermal radiation characteristics.

Protein Phosphatase PP2C19 Controls Hypocotyl Phototropism Through the Phosphorylation Modification of NPH3 in Arabidopsis.

Plants exhibit shoot growth in the direction of the light source to facilitate photosynthesis, known as positive phototropism. In Arabidopsis hypocotyl phototropism, it is thought that a gradient of the signal intensity of the blue light photoreceptor phototropin1 (phot1) between the light-irradiated and shaded sides leads to the differential growth of hypocotyls. The intensity of phot1 signal is regulated not only by the protein kinase activity of phot1 but also by the phosphorylation status of the NONPHOTOTROPIC HYPOCOTYL3 (NPH3) protein, which has a dark form and a blue light form of the phosphorylation modification. Previous studies have shown that phot1 drives the forward reaction from the dark form to the blue light form of NPH3. However, the molecular mechanism underlying the reverse reaction remains unknown. Here, we show that protein phosphatase PP2C19 controls the reverse reaction that converts the blue light form of NPH3 to the dark form of NPH3. The PP2C19 protein possesses the PP2C domain, two cNMP-binding domains, and the protein kinase domain. Similar to phot1 and NPH3, PP2C19 localizes to the plasma membrane, and its PP2C domain is necessary and sufficient for PP2C19 function in hypocotyl phototropism. The pp2c19 mutants show abnormalities in second positive hypocotyl phototropism with a delay in the reverse reaction of NPH3 phosphorylation modification. The present study suggests that continuous blue light irradiation induces an equilibrium state of the reversible reaction of NPH3 phosphorylation, which acts as a phot1 signaling gradient with phot1 kinase activity to induce the second positive phototropism.

Plasmonic Silver Nanoparticles Facilitate Electron Emission from Diamond upon Sun‐Like Excitation

AbstractThe development of a stable, non‐toxic material that emits electrons following absorption of visible light may have a major impact on the solar photocatalysis of difficult reactions such as CO2 and N2 reduction, as well as for targeted chemical transformations in general. Diamond is a good candidate, however it is a wide bandgap material requiring deep UV photons ( <227 nm) to promote electrons from the valence band into the conduction band. Embedding silver nanoparticles under the diamond surface allows the photoconductivity of the diamond in the spectral region of the surface plasmon resonance to be increased, while also leading to an enhancement of visible light photoemission. Considering the low intensity of the light sources used in this work and the spectral properties of the enhanced photoconductivity and photoemission a mechanism based on plasmonically enhanced photoconductivity which in turn allows surface states emptied by photoemission to be recharged thus leading to enhanced photoemission in the visible range is proposed.

PSNet: A non-uniform illumination correction method for underwater images based pseudo-siamese network

Autonomous underwater vehicles (AUVs) based on visual perception play an important role in maritime operations. However, underwater environment often suffers from poor lighting conditions, making the utilization of artificial light sources necessary. This reliance on artificial lighting frequently results in non-uniform illumination. Furthermore, the absorption and scattering effects of water cause further degradation, such as color distortion and blurring of details. To address these challenges, we propose a pseudo-siamese network, named PSNet, designed for underwater optical image enhancement. PSNet separates the non-uniformly illuminated layer from the optimally uniformly illuminated image and utilizes a cascading iteration strategy to enhance the image details. To achieve a better balance prediction quality, we introduce structure loss and residual reconstruction loss as additional guides for model learning. Additionally, we incorporate a color consistency loss to mitigate color distortion. To address the lack of training data, we develop a non-uniform illumination model and generate a dataset that includes both non-uniformly illuminated layers and uniformly illuminated images. Through comprehensive experimental evaluations, PSNet significantly enhances the visual quality of underwater optical images and consistently outperforms state-of-the-art approaches in multiple performance metrics.

Analytical Solution of Rate Equations Including Frequency Chirp of Modulated Quantum-Well Laser with Carrier Transport Processes

When used as light sources in modern fiber communication systems, the modulation bandwidth and chirp are crucial characteristics of high-speed quantum well (QW) lasers. These parameters are primarily constrained by two factors; namely, the transport of charge carriers in the separate confinement heterojunction (SCH) layer and their escape processes in the QW. To analyze the frequency chirp theoretically, a fourth rate equation is added to the existing system of three coupled rate equations, which describe the photon number in the QW and carrier numbers in both the QW and SCH layers. This study employs small-signal analysis to linearize these coupled equations and derives analytical expressions for both the intensity modulation (IM) response and its associated frequency chirp. The chirp is quantified using two metrics, first the chirp per modulated current (CCR), and second the chirp per modulated power (CPR). These analytical expressions are presented in a generalized form, making them applicable to any nonlinear gain mathematical formulation found in the literature. Through numerical calculations applied to high-speed QW lasers, we investigate the individual effects of transport and escape times on the frequency chirp. Our findings demonstrate that CCR reaches its minimum under two specific conditions: when the transport process is relaxed with a relatively long transport time, and when carrier escape in the QW occurs rapidly with a very short escape time. Notably, we found that CPR remains independent of the transport processes.