Red Wavelengths Research Articles

Light at night: effect on the daily clock, learning, memory, cognition, and expression of transcripts in different brain regions of rat.

The rapid increase in urbanization is altering the natural composition of the day-night light ratio. The light/dark cycle regulates animal learning, memory, and mood swings. A study was conducted to examine the effect of different quantity and quality of light at night on the daily clock, learning, memory, cognition, and expression of transcripts in key learning centers. Treatment was similar for experiments one to three. Rats were exposed for 30days to 12h light and 12h dark with a night light of 2lx (dLAN group), 250lx (LL), or without night light (LD). In experiment one, after 28days, blood samples were collected and 2days later, animals were exposed to constant darkness. In experiment two, after 30days of treatment, animals were subjected to various tests involving learning, memory, and cognition. In experiment three, after 30days of treatment, animals were sampled, and transcript levels of brain-derived neurotrophic factor, tyrosine kinase, Growth-Associated Protein 43, Neurogranin, microRNA-132, cAMP Response Element-Binding Protein, Glycogen synthase kinase-3β, and Tumor necrosis factor α were measured in hippocampus, thalamus, and cortex tissues. In experiment four, animals were exposed to night light of 0.019W/m2 but of either red (640nm), green (540nm), or blue (450nm) wavelength for 30days, and similar tests were performed as mentioned in experiment 2. While in experiment five, after 30days of respective wavelength treatments, all animals were sampled for gene expression studies. Our results show that exposure to dLAN and LL affects the daily clock as reflected by altered melatonin secretion and locomotor activity, compromises the learning, memory, and cognitive ability, and alterations in the expression levels of transcripts in the hypothalamus, cortex, and thalamus. The effect is night light intensity dependent. Further, blue light at night has less drastic effects than green and red light. These results could be of the potential use of framing the policies for the use of light at night.

Leaf Spectral Analysis for Detection and Differentiation of Three Major Rice Diseases in the Philippines

Monitoring the plant’s health and early detection of disease are essential to facilitate effective management, decrease disease spread, and minimize yield loss. Spectroscopic techniques in remote sensing offer less laborious methods and high spatiotemporal scale to monitor diseases in crops. Spectral measurements during the development of disease infection may reveal differences among diseases and determine the stage it can be effectively detected. In this study, spectral analysis was performed over the visible and near-infrared (400–850 nm) portions of the spectrum to detect and differentiate three major rice diseases in the Philippines, namely tungro, BLB, and blast disease. Reflectance of infected rice leaves was recorded repeatedly from inoculation to the late stage of each disease. Results show that spectral reflectance is characteristically affected by each disease, resulting in different spectral, signature sensitivity, and first-order derivatives. Red and red-edge wavelength ranges are the most sensitive to the three diseases. Near-infrared wavelengths decreased as tungro and blast diseases progressed. In addition, the spectral reflectance was resampled to common reflectance sensitivity bands of optical sensors and used in the cluster analysis. It showed that BLB and blast can be detected in the early disease stage on the IRRI Standard Evaluation System (SES) scale of 1 and 3, respectively. Alternatively, tungro was detected in its later stage, with an 11–30% height reduction and no distinct yellow to yellow-orange discoloration (5 SES scale). Three regression techniques, Partial Least Square, Random Forest, and Support Vector Regression were performed separately on each disease to develop models predicting its severity. The validation results of the PLSR and SVR models in tungro and blast show accuracy levels that are promising to be used in estimating the severity of the disease in leaves while RFR shows the best results for BLB. Early disease detection and regression models from spectral measurements and analysis for disease severity estimation can help in disease monitoring and proper disease management implementation.

Deciphering the Effect of Light Wavelengths in Monilinia spp. DHN-Melanin Production and Their Interplay with ROS Metabolism in M. fructicola.

Pathogenic fungi are influenced by many biotic and abiotic factors. Among them, light is a source of information for fungi and also a stress factor that triggers multiple biological responses, including the activation of secondary metabolites, such as the production of melanin pigments. In this study, we analyzed the melanin-like production in in vitro conditions, as well as the expression of all biosynthetic and regulatory genes of the DHN-melanin pathway in the three main Monilinia species upon exposure to light conditions (white, black, blue, red, and far-red wavelengths). On the other hand, we analyzed, for the first time, the metabolism related to ROS in M. fructicola, through the production of hydrogen peroxide (H2O2) and the expression of stress-related genes under different light conditions. In general, the results indicated a clear importance of black light on melanin production and expression in M. laxa and M. fructicola, but not in M. fructigena. Regarding ROS-related metabolism in M. fructicola, blue light highlighted by inhibiting the expression of many antioxidant genes. Overall, it represents a global description of the effect of light on the regulation of two important secondary mechanisms, essential for the adaptation of the fungus to the environment and its survival.

High self-powered UV–Visible photoresponse in ZnO/CuO heterostructure photodetectors, the influence of ZnO window layer thickness

In this study, we have fabricated ZnO/CuO heterostructure photodiodes on FTO substrate using the RF-sputtering method and investigated the influence of the ZnO thickness (390 and 470 nm) on their photoresponse in the wide range of UV to red wavelengths. The layers were characterized by FESEM, XRD, Raman, PL, and UV–Vis. Spectra, also I–V, I–V–T (295–340 K), and I-t in the dark and under illumination. We found: (1) the constituent layers have a polycrystalline nature, monoclinic phases for CuO and wurtzite phase for ZnO layers; (2) in addition to rectifying behavior, the I–V–T analysis confirmed that the current mechanism of these junctions follows the recombination model; (3) both samples have the potential of photovoltaic properties with self-powered ability; (4) sample with thinner ZnO layer has the highest photoresponse ratio (ILight/IDark) of 5.5 × 104–2.6 × 103 through UV to red light illumination and fast response time of 45–50 ms.

Efficient Surface Structuring of Photomechanical Solid Polymers by Near-Zero Light Absorption

Mechanics enabled by photon absorption generates work from materials and is perhaps one of the most important applications of light-active matter, which mediates an intensity-to-stress transduction and moves in intensity gradients. Photomechanics can be put at work in surface structuring of materials, which has applications in several areas of science and engineering including photonics and biology and medicine. We demonstrate that photosensitive materials can be unexpectedly micro- and nanotextured by single-step irradiation with weakly absorbed low-power red light. We report highly efficient surface structuring induced by interference patterns of two coherent nonresonant red (wavelength of 632.8 nm), less than 5 mW, laser beams operating in the near-zero absorption tail of azo-polymer films with optical densities in the 0.02–0.09 range, i.e., 80 – 95% light transmission. The heights of the observed structures are comparable to those obtained by resonant absorption, a feature that is counterintuitive and thus never reported to date. Low- and high-energy n – π* and π – π* excitations of the azo dye are equally efficient in inducing isomerization and mass motion of polymers. Our work is of central importance to photomechanics, and to surface texturing in particular, since it demonstrates that efficient material motion can be driven by weekly absorbed, i.e., low-energy excitation, low-power red light, in solid films of polymers well below the glass transition temperature, pointing to possible biological and cost-effective industrial applications.

Simultaneous RGB generation in domain engineered QPM devices using type 0 DFG process

We have theoretically demonstrated the simultaneous generation of red (R), green (G), and blue (B) wavelengths by employing the type-0 quasi-phase-matched (QPM) difference frequency generation (DFG) process in congruent LiNbO3 crystal. Various domain-engineered QPM structures are presented and analysed, aiming to achieve an excellent spectral response. The RGB emissions were observed to vary from 632 nm to 656 nm for red, 504 nm to 532 nm for green, and 449 nm to 484 nm for blue, respectively, for different configurations of input pump, operating temperature, and phase matching periods. A maximum shift of about 10 nm to 20 nm was noticed in the spectral position of the DFG peaks when the operating temperature varies from 25 °C to 60 °C. We have also investigated the effect of pump detuning and random domain fluctuations over the phase matching point on the DFG spectrum. Further, we have addressed the advantages of introducing a phase shifter (PS) domain in the periodically poled lithium niobate (PPLN) to produce excellent equal intensity RGB peaks in a single device for their potential application in a laser-based projection display system.

The Role of Blue and Red Light in the Orchestration of Secondary Metabolites, Nutrient Transport and Plant Quality.

Light is a fundamental environmental parameter for plant growth and development because it provides an energy source for carbon fixation during photosynthesis and regulates many other physiological processes through its signaling. In indoor horticultural cultivation systems, sole-source light-emitting diodes (LEDs) have shown great potential for optimizing growth and producing high-quality products. Light is also a regulator of flowering, acting on phytochromes and inducing or inhibiting photoperiodic plants. Plants respond to light quality through several light receptors that can absorb light at different wavelengths. This review summarizes recent progress in our understanding of the role of blue and red light in the modulation of important plant quality traits, nutrient absorption and assimilation, as well as secondary metabolites, and includes the dynamic signaling networks that are orchestrated by blue and red wavelengths with a focus on transcriptional and metabolic reprogramming, plant productivity, and the nutritional quality of products. Moreover, it highlights future lines of research that should increase our knowledge to develop tailored light recipes to shape the plant characteristics and the nutritional and nutraceutical value of horticultural products.

Red, orange, and dual wavelength vortex emission from Pr:WPFGF fiber laser using a microscope slide output coupler.

Visible vortex beams have a large array of applications; however, the sources are often large or complex. Here, we present a compact vortex source with red, orange, and dual wavelength emission. This Pr:Waterproof Fluoro-Aluminate Glass fiber laser uses a standard microscope slide as an interferometric output coupler, yielding high quality first order vortex modes in a compact setup. We further demonstrate the broad (∼5 nm) emission bands in the orange (610 nm), red (637 nm) and near-infrared regions (698 nm), with the potential for green (530 nm) and cyan (485 nm) emission. This is a low-cost, compact and accessible device giving high quality modes for visible vortex applications.

Links between light availability and spectral properties of forest floor in European forests

Remote sensing using spectral data has been commonly applied to retrieve tree layer properties while the monitoring of forest floor remains a less studied topic. We investigated the links between light availability at forest floor, and forest floor's spectral reflectance properties (350–2500 nm) and fractional cover across boreal and temperate Europe. We hypothesized that tree canopy structure (and thus, light availability at forest floor) is linked not only to the vegetation composition of forest floor, as has been shown previously, but also to forest floor's spectral reflectance properties, and that these relationships differ between forest biomes. Data were collected in situ from a total of 67 forest stands in southern boreal, hemiboreal, temperate floodplain, and temperate mountain sites. The variation of light availability at forest floor was linked to both the forest floor's composition and spectral reflectance properties. Each study site exhibited site-specific spectral features and a different mean reflectance spectrum. Openness in tree canopies was related to an increase in the fractional cover of vascular plants and to a decrease of plant litter, consequently enhancing the forest floors’ spectral absorptance features in the red and shortwave-infrared wavelengths, as well as reflectance in the near-infrared region. Also, the variations of normalized difference index values and red edge positions as functions light availability at forest floor and forest floor's composition were different for each site. Our results suggest that incorporating biome-specific relationships between tree canopy structure and forest floor reflectance properties would improve interpretation of optical remote sensing data. The measurement data are openly available.

Red and green plasmonic-induced random laser in two-dimensional square array onto glass substrate

Red and green lasers are preferred with a multi-layered 2D structure onto a curved glass substrate (clock glass), a charge-coupled camera device (CCD) as a seal, and a gold nanostructure with rhodamine dye. For this purpose, a layer of Kapton tape was attached to the CCD by applying pressure to get a two-dimensional structure and transfer onto the glass, then the gold nanostructure was covered inside that glass substance. To achieve random laser beams of multiple wavelengths, this two-sided curved glass substrate was coated with rhodamine dye. The sample was pumped by a nanosecond green laser. Lasers from band-edge lattice plasmons were collected into arrays of plasmonic nanorods in a homogeneous environment by a spectrophotometer. Our results revealed emission peaks for red and green wavelengths with the lowest value of the laser threshold.

Non-parametric galaxy morphology from stellar and nebular emission with the CALIFA sample

Aims. We present a non-parametric morphology analysis of the stellar continuum and nebular emission lines for a sample of local galaxies. We explore the dependence of the various morphological parameters on wavelength and morphological type. Our goal is to quantify the difference in morphology between the stellar and nebular components. Methods. We derived the non-parametric morphological indicators of 364 galaxies from the Calar Alto Legacy Integral Field Area (CALIFA) Survey. To calculate those indicators, we applied the StatMorph package on the high-quality integral field spectroscopic data cubes, as well as to the most prominent nebular emission-line maps, namely [O III]λ5007, Hα, and [N II]λ6583. Results. We show that the physical size of galaxies, M20 index, and concentration have a strong gradient from blue to red optical wavelengths. We find that the light distribution of the nebular emission is less concentrated than the stellar continuum. A comparison between the non-parametric indicators and the galaxy physical properties revealed a very strong correlation of the concentration with the specific star formation rate and morphological type. Furthermore, we explore how the galaxy inclination affects our results. We find that edge-on galaxies show a more rapid change in physical size and concentration with increasing wavelength due to the increase in the optical free path. Conclusions. We conclude that the apparent morphology of galaxies originates from the pure stellar distribution, but the morphology of the interstellar medium presents differences with respect to the morphology of the stellar component. Our analysis also highlights the importance of dust attenuation and galaxy inclination in the measurement of non-parametric morphological indicators, especially in the wavelength range 4000−5000 Å.

Assessing Within-Field Variation in Alfalfa Leaf Area Index Using UAV Visible Vegetation Indices

This study examines the use of leaf area index (LAI) to inform variable-rate irrigation (VRI) for irrigated alfalfa (Medicago sativa). LAI is useful for predicting zone-specific evapotranspiration (ETc). One approach toward estimating LAI is to utilize the relationship between LAI and visible vegetation indices (VVIs) using unmanned aerial vehicle (UAV) imagery. This research has three objectives: (1) to measure and describe the within-field variation in LAI and canopy height for an irrigated alfalfa field, (2) to evaluate the relationships between the alfalfa LAI and various VVIs with and without field average canopy height, and (3) to use UAV images and field average canopy height to describe the within-field variation in LAI and the potential application to VRI. The study was conducted in 2021–2022 in Rexburg, Idaho. Over the course of the study, the measured LAI varied from 0.23 m2 m−2 to 11.28 m2 m−2 and canopy height varied from 6 cm to 65 cm. There was strong spatial clustering in the measured LAI but the spatial patterns were dynamic between dates. Among eleven VVIs evaluated, the four that combined green and red wavelengths but excluded blue wavelengths showed the most promise. For all VVIs, adding average canopy height to multiple linear regression improved LAI prediction. The regression model using the modified green–red vegetation index (MGRVI) and canopy height (R2 = 0.93) was applied to describe the spatial variation in the LAI among VRI zones. There were significant (p < 0.05) but not practical differences (<15%) between pre-defined zones. UAV imagery coupled with field average canopy height can be a useful tool for predicting LAI in alfalfa.

Stable tissue-mimicking phantoms for longitudinal multimodality imaging studies that incorporate optical, CT, and MRI contrast.

Tissue phantoms that mimic the optical and radiologic properties of human or animal tissue play an important role in the development, characterization, and evaluation of imaging systems. Phantoms that are easily produced and stable for longitudinal studies are highly desirable. A new type of long-lasting phantom was developed with commercially available materials and was assessed for fabrication ease, stability, and optical property control. Magnetic resonance imaging (MRI) and x-ray computed tomography (CT) contrast properties were also evaluated. A systematic investigation of relationships between concentrations of skin-like pigments and composite optical properties was conducted to realize optical property phantoms in the red and near-infrared (NIR) wavelength range that also offered contrast for CT and MRI. Phantom fabrication time was and did not involve any heating or cooling processes. Changes in optical properties were over a 12-month period. Phantom optical and spectral features were similar to human soft tissue over the red to NIR wavelength ranges. Pigments used in the study also had CT and MRI contrasts for multimodality imaging studies. The phantoms described here mimic optical properties of soft tissue and are suitable for multimodality imaging studies involving CT or MRI without adding secondary contrast agents.

Effects of Light-Emitting Diodes (LEDs) on Growth, Nitrates and Osmoprotectant Content in Microgreens of Aromatic and Medicinal Plants

Microgreens are receiving increasing attention due to their high content of bioactive components and their importance to human health. These emerging food products can be obtained from the seeds of different plant species, including aromatic herbs. Aromatic microgreens are gaining popularity as new functional food products. In this study, we investigated the effects of different light-emitting diode (LED) lamp spectra on the growth, pigments, nitrates, and osmoprotectant content of microgreens of Ocimum basilicum L., Trigonella foenum-graecum, Anethum graveolens, and Anthriscus cerefolium plants. Three types of artificial LED lamps were used: T0 as artificial white light, T1 as a continuous light-emitting diode with a longer blue wavelength, and T2 as a continuous light-emitting diode with a longer red wavelength. The results obtained showed that the three types of LED light had significant effects on the different parameters studied. In relation to growth parameters, such as fresh weight (FW) and microgreen height (H), the T2 treatment was most effective for fenugreek, dill, and chervil. However, in basil plants, FW and H values were higher under T1 treatment. Regarding nitrate accumulation, both T1 and T2 treatments reduced the content of this nutrient in the different species studied here. Finally, levels of chlorophyll, carotenoid, glucose, proline, and proteins were all higher in plants cultivated under T1 and T2 treatments than in control plants.

Light, Water, and Melatonin: The Synergistic Regulation of Phase Separation in Dementia.

The swift rise in acceptance of molecular principles defining phase separation by a broad array of scientific disciplines is shadowed by increasing discoveries linking phase separation to pathological aggregations associated with numerous neurodegenerative disorders, including Alzheimer's disease, that contribute to dementia. Phase separation is powered by multivalent macromolecular interactions. Importantly, the release of water molecules from protein hydration shells into bulk creates entropic gains that promote phase separation and the subsequent generation of insoluble cytotoxic aggregates that drive healthy brain cells into diseased states. Higher viscosity in interfacial waters and limited hydration in interiors of biomolecular condensates facilitate phase separation. Light, water, and melatonin constitute an ancient synergy that ensures adequate protein hydration to prevent aberrant phase separation. The 670 nm visible red wavelength found in sunlight and employed in photobiomodulation reduces interfacial and mitochondrial matrix viscosity to enhance ATP production via increasing ATP synthase motor efficiency. Melatonin is a potent antioxidant that lowers viscosity to increase ATP by scavenging excess reactive oxygen species and free radicals. Reduced viscosity by light and melatonin elevates the availability of free water molecules that allow melatonin to adopt favorable conformations that enhance intrinsic features, including binding interactions with adenosine that reinforces the adenosine moiety effect of ATP responsible for preventing water removal that causes hydrophobic collapse and aggregation in phase separation. Precise recalibration of interspecies melatonin dosages that account for differences in metabolic rates and bioavailability will ensure the efficacious reinstatement of the once-powerful ancient synergy between light, water, and melatonin in a modern world.

Effect of different LED wavelengths on growth, chlorophyll and anthocyanin content of purple-red pakchoi (Brassica rapa chineensis) in indoor vertical farming

Understanding the effects of different light wavelengths on plant growth and the accumulation of essential nutrients like antioxidants is critical for obtaining optimal light conditions for the production of high-quality vegetables in indoor vertical farming. Purplered pakchoi (Brassica rapa chineensisis) is a fast-growing brassiceous vegetable. This vegetable is known to have health-promoting properties due to anthocyanin, which is a crucial antioxidant in the diet. This crop was used to evaluate the effects of red (RL), blue (BL), and green (GL) wavelengths on plant morphology, relative chlorophyll content, and phytochemical accumulation (anthocyanin). Light treatments consisted of three different wavelength combinations: a) full spectrum, white light (WL) as a control (the proportions of RL, BL and GL wavelengths were 42%, 15% and 43%, respectively); b) combination RL81BL19 (the proportions of RL and BL wavelengths were set at 81% and 19%, respectively); and c) combination RL70BL21GL9 (the proportions of RL, BL and GL wavelengths were set at 70%, 21% and 9%, respectively). The experiment was carried out in the LED Light Research Lab (MARDI, Serdang), a walk-in chamber with a 12-hour photoperiod. The temperature, CO2, and relative humidity levels in the LED light lab were kept under control. Plant width and height were found to be most prominent in plants exposed under RL81BL19 LED light, followed by RL70BL21GL9, while plants grown under WL were relatively small. Purple-red pakchoi exposed to a combination of RL and BL, supplemented with GL light treatment, had a slightly smaller plant height and width than plants exposed to RL81BL19 light treatment. Similar results were obtained in terms of shoot fresh and dry weight, with the RL81BL19 having the highest shoot fresh and dry weight, followed by the RL70BL21GL9 and WL light exposure plants. Furthermore, when compared to other treatments, purple-red pakchoi treated with RL81BL19 light had a significantly higher content (p<0.05) of chlorophyll and anthocyanin. This finding indicated that GL light treatment has no direct effect on overall growth, chlorophyll accumulation, or anthocyanin content in purple-red pakchoi. This study found that the RL81BL19 wavelength is the best LED light treatment for purple-red pakchoi production in indoor vertical farming.

Color-resolved Cherenkov imaging allows for differential signal detection in blood and melanin content.

High-energy x-ray delivery from a linear accelerator results in the production of spectrally continuous broadband Cherenkov light inside tissue. In the absence of attenuation, there is a linear relationship between Cherenkov emission and deposited dose; however, scattering and absorption result in the distortion of this linear relationship. As Cherenkov emission exits the absorption by tissue dominates the observed Cherenkov emission spectrum. Spectroscopic interpretation of this effects may help to better relate Cherenkov emission to ionizing radiation dose delivered during radiotherapy. In this study, we examined how color Cherenkov imaging intensity variations are caused by absorption from both melanin and hemoglobin level variations, so that future Cherenkov emission imaging might be corrected for linearity to delivered dose. A custom, time-gated, three-channel intensified camera was used to image the red, green, and blue wavelengths of Cherenkov emission from tissue phantoms with synthetic melanin layers and varying blood concentrations. Our hypothesis was that spectroscopic separation of Cherenkov emission would allow for the identification of attenuated signals that varied in response to changes in blood content versus melanin content, because of their different characteristic absorption spectra. Cherenkov emission scaled with dose linearly in all channels. Absorption in the blue and green channels increased with increasing oxy-hemoglobin in the blood to a greater extent than in the red channel. Melanin was found to absorb with only slight differences between all channels. These spectral differences can be used to derive dose from measured Cherenkov emission. Color Cherenkov emission imaging may be used to improve the optical measurement and determination of dose delivered in tissues. Calibration for these factors to minimize the influence of the tissue types and skin tones may be possible using color camera system information based upon the linearity of the observed signals.

The evolution of the green-light-sensitive visual opsin genes (RH2) in teleost fishes

Vertebrates have four visual cone opsin classes that mediate sensitivity from ultraviolet to red wavelengths of light. The rhodopsin-like 2 (RH2) opsin is sensitive to the central mostly green part of the spectrum. While lost in some terrestrial vertebrates (mammals), the RH2 opsin gene has proliferated during the evolution of teleost fishes. Here, we investigated the genomes of 132 extant teleosts and found between zero and eight RH2 gene copies per species. The RH2 gene shows a dynamic evolutionary history with repeated gene duplications, gene losses, and gene conversions affecting entire orders, families, and species. At least four ancestral duplications provided the substrate for today’s RH2 diversity, with duplications occurring in the common ancestors of Clupeocephala (twice), Neoteleostei, and likely Acanthopterygii as well. Despite these evolutionary dynamics, we identified conserved RH2 synteny in two main gene clusters; the slc6A13/synpr cluster is highly conserved within Percomorpha and also present across most teleosts, including Otomorpha, Euteleostei and in parts in tarpons (Elopomorpha), and the mutSH5 cluster, which is specific for Otomorpha. When comparing the number of visual opsin genes (SWS1, SWS2, RH2, LWS, and total cone opsins) with habitat depth, we found that deeper-dwelling species had less (or none) long-wavelength-sensitive opsins. Using retinal/eye transcriptomes in a phylogenetic representative dataset of 32 species, we show that if present in the genome, RH2 is expressed in most fishes except for some species within the tarpons, characins, and gobies (and Osteoglossomorpha and some other characin species have lost the gene). Those species instead express a green-shifted long-wavelength-sensitive LWS opsin. Our study applies modern genomic and transcriptomic tools within a comparative framework to elucidate the evolutionary history of the visual sensory system in teleost fishes.

A flash of polarized optical light points to an aspherical ‘cow’

ABSTRACTThe astronomical transient AT2018cow is the closest example of the new class of luminous, fast blue optical transients (FBOTs). Liverpool telescope RINGO3 observations of AT 2018cow are reported here, which constitute the earliest polarimetric observations of an FBOT. At $5.7\, \mathrm{days}$ post-explosion, the optical emission of AT2018cow exhibited a chromatic polarization spike that reached $\sim 7{{\ \rm per\ cent}}$ at red wavelengths. This is the highest intrinsic polarization recorded for a non-relativistic explosive transient and is observed in multiple bands and at multiple epochs over the first night of observations, before rapidly declining. The apparent wavelength dependence of the polarization may arise through depolarization or dilution of the polarized flux, due to conditions in AT 2018cow at early times. A second ‘bump’ in the polarization is observed at blue wavelengths at $\sim 12\, \mathrm{days}$. Such a high polarization requires an extremely aspherical geometry that is only apparent for a brief period (<1 d), such as shock breakout through an optically thick disk. For a disk-like configuration, the ratio of the thickness to radial extent must be $\sim 10{{\ \rm per\ cent}}$.

Recent Advances in Micro-LEDs Having Yellow–Green to Red Emission Wavelengths for Visible Light Communications

Visible light communication (VLC), which will primarily support high-speed internet connectivity in the contemporary world, has progressively come to be recognized as a significant alternative and reinforcement in the wireless communication area. VLC has become more popular recently because of its many advantages over conventional radio frequencies, including a higher transmission rate, high bandwidth, low power consumption, fewer health risks, and reduced interference. Due to its high-bandwidth characteristics and potential to be used for both illumination and communications, micro-light-emitting diodes (micro-LEDs) have drawn a lot of attention for their use in VLC applications. In this review, a detailed overview of micro-LEDs that have long emission wavelengths for VLC is presented, along with their related challenges and future prospects. The VLC performance of micro-LEDs is influenced by a number of factors, including the quantum-confined Stark effect (QCSE), size-dependent effect, and droop effect, which are discussed in the following sections. When these elements are combined, it has a major impact on the performance of micro-LEDs in terms of their modulation bandwidth, wavelength shift, full-width at half maximum (FWHM), light output power, and efficiency. The possible challenges faced in the use of micro-LEDs were analyzed through a simulation conducted using Crosslight Apsys software and the results were compared with the previous reported results. We also provide a brief overview of the phenomena, underlying theories, and potential possible solutions to these issues. Furthermore, we provide a brief discussion regarding micro-LEDs that have emission wavelengths ranging from yellow-green to red colors. We highlight the notable bandwidth enhancement for this paradigm and anticipate some exciting new research directions. Overall, this review paper provides a brief overview of the performance of VLC-based systems based on micro-LEDs and some of their possible applications.