Green Light Wavelength Research Articles

Effect of distributed Bragg reflectors on optoelectronic characteristics of GaN-based flip-chip light-emitting diodes

Distributed Bragg reflectors have been widely utilized in GaN-based flip-chip light-emitting diodes (FCLEDs) owing to their excellent reflection performance. Recently, wide reflected angle DBR (WRA-DBR) has been suggested to enhance the optical characteristics of GaN-based FCLEDs by incorporating multiple sub-DBRs with varying central wavelengths. However, the reflectivity of WRA-DBR decreases at large incident angle from 425 nm to 550 nm, which restricts further optical performance improvement of FCLEDs. Here, we demonstrate a quintuple-stack DBR comprised of five sub-DBRs. The quintuple-stack DBR possesses a high reflectivity (>97.5%) for incident angles below 50° within the blue and green light wavelength ranges. Compared to WRA-DBR, quintuple-stack DBR exhibits a higher reflectivity in wavelength range of 425 nm to 550 nm and thinner multilayer thicknesses. Furthermore, stronger electric field intensities exist in the top facet and sidewalls of FCLED with quintuple-stack DBR, revealing that quintuple-stack DBR is beneficial for enhancing the light extraction efficiency. As a result, the light output power of FCLED with quintuple-stack DBR is ∼3% higher than that of FCLED with WRA-DBR at 750 mA.

Morpho-physio-biochemical, molecular, and phytoremedial responses of plants to red, blue, and green light: a review.

Light is a basic requirement to drive carbon metabolism in plants and supports life on earth. Spectral quality greatly affects plant morphology, physiology, and metabolism of various biochemical pathways. Among visible light spectrum, red, blue, and green light wavelengths affect several mechanisms to contribute in plant growth and productivity. In addition, supplementation of red, blue, or green light with other wavelengths showed vivid effects on the plant biology. However, response of plants differs in different species and growing conditions. This review article provides a detailed view and interpretation of existing knowledge and clarifies underlying mechanisms that how red, blue, and green light spectra affect plant morpho-physiological, biochemical, and molecular parameters to make a significant contribution towards improved crop production, fruit quality, disease control, phytoremediation potential, and resource use efficiency.

Day and night continuous high-resolution shallow-water depth detection with single-photon underwater lidar.

Single-photon lidar has emerged as a strong technology for bathymetric measurements. However, its heightened sensitivity additionally makes it susceptible to solar radiation noise, particularly in the green light wavelength where solar radiation is strong, posing challenges for its daytime operation. To address this issue, a single-photon underwater lidar system is proposed and demonstrated. This scheme has these features. 1) Underwater applications not only mitigate the impact of the air-water interface on laser transmission but also significantly attenuate solar radiation reaching the lidar due to the absorption and scattering properties of water. 2) The telescope is designed with a small aperture and narrow field of view to significantly suppress solar radiation. 3) A combination of a narrowband laser and narrowband filter technique is effectively employed to minimize residual solar radiation, thus enabling continuous bathymetric observation capabilities during both day and night. 4) After acquiring the backscattered signal from the bottom, a water depth extraction algorithm utilizing bi-Gaussian fitting is proposed. To demonstrate the robustness of the lidar and the effectiveness of the algorithm, the underwater single-photon lidar system is deployed on a ship to conduct cruise surveys of two bays in the nearshore area, as well as a full-day stationary observation experiment. The lidar measurements are highly consistent with the synchronized sonar observations. The full-day stationary observation experiment showcased its capability to deliver continuous measurements throughout the day and night. These results demonstrate the potential of the system in various applications, including high-precision underwater terrain mapping, obstacle avoidance for underwater platforms, and underwater target imaging.

(Sr, Ca)AlSiN3:Eu2+ Phosphor-Doped YAG:Ce3+ Transparent Ceramics as Novel Green-Light-Emitting Materials for White LEDs.

In this work, based on Y3Al5O12:Ce3+ (YAG:Ce3+) transparent ceramic and (Sr, Ca)AlSiN3:Eu2+ phosphors, novel green-light-emitting materials were systematically studied. YAG:Ce3+ transparent ceramics with different doping-concentrations, from 0% to 1% (Sr, Ca)AlSiN3:Eu2+ phosphors, were fabricated by dry pressing and vacuum sintering. The serial phosphor ceramics had 533 nm green-light emission when excited by 460 nm blue light. The PL, PLE, and chromaticity performances were measured, indicating that more of the green-light component was emitted with the increase in doping concentration. The addition of (Sr, Ca)AlSiN3:Eu2+ phosphor increased the green-light wavelength area and improved the quantum yield (QY) of the YAG:Ce3+ ceramic matrix. The phase composition, microstructure, crystal-field structure and phosphor distribution of (Sr, Ca)AlSiN3:Eu2+ phosphor-doped YAG:Ce3+ transparent ceramics were investigated, to explore the microscopic causes of the spectral changes. Impressively, (Sr, Ca)AlSiN3:Eu2+ phosphors were distributed homogeneously, and the pinning effect of phosphor caused the suppression of grain growth. The novel materials could provide an effective strategy for full-spectrum white lighting and displaying applications in the future.

Organic bulk heterojunction enabled with nanocapsules of hydrate vanadium pentaoxide layer for high responsivity self-powered photodetector

This article demonstrates the fabrication of organic-based devices using a low-cost solution-processable technique. A blended heterojunction of chlorine substituted 2D-conjugated polymer PBDB-T-2Cl, and PC71BM supported nanocapsules hydrate vanadium penta oxides (HVO) as hole transport layer (HTL) based photodetector fabricated on an ITO coated glass substrate under ambient condition. The device forms an excellent organic junction diode with a good rectification ratio of ~200. The device has also shown excellent photodetection properties under photoconductive mode (at reverse bias) and zero bias for green light wavelength. A very high responsivity of ~6500 mA/W and high external quantum efficiency (EQE) of 1400% have been reported in the article. The proposed organic photodetector exhibits an excellent response and recovery time of ~30 and ~40 ms, respectively.

An empirical relationship between PM2.5 and aerosol optical depth from MODIS satellite images for spatial simulation over Ho Chi Minh city

Air quality in megacities has been a pressing concern of environmental managers and scientists for decades. Indeed, particulate matter (PM), especially PM2.5, is considered a dangerousparticle that is harmful to human health. The current sparse monitoring network in Ho Chi Minh city (HCMC) does not accurately reflect the spatial distribution of fine particles in ambient air. Therefore, this research examines the relationship between ground-based station data and aerosol optical depth (AOD) imagery from the Moderate Resolution Imaging Spectroradiometer (MODIS) onboard the Terra/Aqua satellite to establish a PM2.5 distribution map of HCMC. PM2.5 concentration values monitored from two ground stations were collocated by time and space with Terra/MODIS AOD data from the period of 2016-2020. Pairs of values were checked for correlation and then fit to several regression functions. The most suitable function was chosen to simulate the quantified PM2.5distributions in the study area. A high correlation between PM2.5 concentrations and AOD at the wavelength of green light (R2=0.810) was found with a linear regression model. The results showed that the highest concentration of PM2.5 was in February, and the mean value was higher than QCVN 05:2013 (32.5 μg/m3compared with 25 μg/m3, annual mean). These results support the need for essential air quality monitoring in HCMC.

Photonic Integrated Chip on TriPleX Platform for Realizing Optical Haar Transform and Compression in the Visible Spectrum

The design and characterization of a new photonic chip on TriPleX <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">TM</sup> integrated platform technology for investigating all-optical Haar transform (HT) based compression in the visible spectrum is proposed. A building block (BB) based on a multimode interference (MMI) structure is designed for green light wavelength (532 nm), enabling the optical HT operation in the circuits of the optical chip. The designed TriPleX chip demonstrates two types of MMI based optical circuits, i.e., restricted interference (RI) and general interference (GI), allowing the implementation of the optical HT and compression on the input image pixels. An optical image compression rate of 75% is achieved for a linear 8-pixels array of an image by the designed circuit in the chip. An experimental coupling ratio (CR) of ~98:2 is obtained by the designed circuit in the chip with identical optical inputs, proving high capability of the proposed design for the realization of optical HT and image compression.

Effects of Light Spectral Quality on the Micropropagated Raspberry Plants during Ex Vitro Adaptation.

This work focuses on developing light environments for the effective regulation of morphogenesis and ex vitro conditions adaptation in micropropagated raspberry plants on the basis of photomorphogenetic control of physiological processes using light-emitting diodes (LEDs). In experiments with cloned plants growing ex vitro in stressful conditions during acclimation, the effects of optical radiation of various spectral combinations from different photosynthetically active radiation (PAR) spectral regions were studied. The data on the plant development and state of the photosynthetic apparatus, features of photosynthetic gas exchange and transpiration, accumulation of photosynthetic pigments, light curves of photosynthesis, and data on growth processes in light modes using combined quasimonochromatic radiation (either mixture of red, green, and blue light or red, far-red, and blue light) with various ratio of the distinct spectral regions were obtained. Photosynthetic apparatus functional activity under different light conditions was studied with chlorophyll fluorescence determination, and plant stress responses to growing under artificial spectral light conditions were characterized. The experiments were accompanied by detailed plant phenotyping at the structural and functional levels. Plant acclimation and photosynthetic improvements in response to added far-red and green light wavelengths to the main red-blue spectrum have been elucidated.

Reacquisition of light-harvesting genes in a marine cyanobacterium confers a broader solar niche

The evolution of phenotypic plasticity, i.e., the environmental induction of alternative phenotypes by the same genotype, can be an important mechanism of biological diversification.1,2 For example, an evolved increase in plasticity may promote ecological niche expansion as well as the innovation of novel traits;3 however, both the role of phenotypic plasticity in adaptive evolution and its underlying mechanisms are still poorly understood.4,5 Here, we report that the Chlorophyll d-producing marine cyanobacterium Acaryochloris marina strain MBIC11017 has evolved greater photosynthetic plasticity by reacquiring light-harvesting genes via horizontal gene transfer. The genes, which had been lost by the A.marina ancestor, are involved in the production and degradation of the light-harvesting phycobiliprotein phycocyanin. A.marina MBIC11017 exhibits a high degree of wavelength-dependence in phycocyanin production, and this ability enables it to grow with yellow and green light wavelengths that are inaccessible to other A.marina. Consequently, this strain has a broader solar niche than its close relatives. We discuss the role of horizontal gene transfer for regaining a lost phenotype in light of Dollo's Law6 that the loss of a complex trait is irreversible.

Effect of green wavelength light on stress and appetite responses of olive flounder (Paralichthys olivaceus) following feed deprivation and re-feeding

Feeding regimes and light may influence the productivity and wellbeing of aquatic animals; however, little is known regarding any interactive effects. We investigated if short-term deprivation and refeeding regimes and green light promotes growth by reducing stress in the olive flounder, using two lights [white fluorescent bulb (white) and green-wavelength LED (green)] in 4 feeding trials (fed 4 weeks, 4F; fasted 1 week/fed 3 weeks, 1S-3F; fasted 2 weeks/fed 2 weeks, 2S-2F; fasted 4 weeks, 4S). At the end of the feeding periods, weight gain rate (WGR), daily feed intake (DFI), and cumulative food intake (CFI) of 4F green group were significantly higher than other groups (p < 0.05), and the 1S-3F green group reached the WGR and DFI of the 4F white group (p> 0.05). Also, 1S-3F green group showed the highest values in feed efficiency (FE) (p < 0.05). In addition, mRNA expressions of neuropeptide Y (NPY), melanin concentrating hormone (MCH), and insulin like growth factor (IGF-1) were significantly higher in the 1S-3F green group at 4 weeks than in the other periods (p < 0.05). Immunohistochemistry (IHC) staining of NPY in diencephalon revealed that the brown colored increased with longer fasting period under white light. These results suggested that the 1S-3F feeding regime in the short term (4 weeks) was the most effective for short-term feed deprivation and re-feeding. Furthermore, green light had an especially beneficial effect that reduced stress and promoted appetite for refeeding in cultured fish. Our findings are expected to work toward a positive aquaculture environment for animal welfare.

A four green-light demultiplexer using a multi gallium nitride slot-waveguide structure

In this work, we introduce a four green-light wavelength splitter device, based on six slot-waveguide structures. Silica and gallium nitride materials were chosen for confining the green light inside the slot-waveguide area in a transverse magnetic field mode. The device functioned as a 1 × 4 demultiplexer, which demultiplexes wavelengths in the green-light band with wavelength range of 500–530 nm with an accurate spacing of 10 nm. The coupling between the six slot-waveguide units was analyzed using the classical mode theory and the full vectorial beam propagation method. Simulation results showed that the four wavelengths could be demultiplexed after a short coupling length of 106.5 μm with low losses around 0.108–0.127 dB, full width at half maximum around 8.99–9.39 nm, and excellent crosstalk around −21.13 to −24.1 dB. The device has the potential to increase data bitrate by utilizing the wavelength division multiplexing technique in visible light communication systems.

Effects of green light on circadian rhythm of the olive flounder Paralichthys olivaceus anaesthetised with clove oil

ABSTRACT We measured the induction and recovery time of anaesthetised olive flounder Paralichthys olivaceus with two concentrations of clove oil (25 and 50 μL/L), under the fluorescent lamp or green-wavelength light. In addition, we investigated their effects on the circadian rhythm after recovery from anaesthesia. We found that with the increase in anaesthesia concentration, induction time decreases and recovery time increases, in both light conditions. However, when anaesthetised with the same concentration of clove oil, induction time remained the same, but the recovery time was significantly decreased under green-wavelength light. The circadian rhythm was evaluated by quantifying the transcript levels of clock genes [period 2 (Per2) and cryptochrome1 (Cry1)] and activities of melatonin for 42 h. In the anaesthesia experimental group, the expression of the clock genes and activities of melatonin were significantly lower than that in the control group, and it was further lowered as the concentration of clove oil was increased. However, the anaesthetised group under green wavelength did not show a significant difference in circadian parameters compared to the control group, over time. This study provides the critical information on the use of clove oil anaesthesia in flounders and shows the effective recovery after anaesthesia upon exposure to green-wavelength light.

Effects of Green Wavelength Light on Antioxidant Responses in Olive Flounder Paralichthys olivaceus Exposed to Starvation and Re-feeding

Effects of Green Wavelength Light on Antioxidant Responses in Olive Flounder Paralichthys olivaceus Exposed to Starvation and Re-feeding

Novel Design and Evaluation of an Automatic and Portable Phototherapy Device Using for Newborn Jaundice Treatment

Jaundice in infants is one of the most common diseases at birth. In preterm infants, the risk is more than 80%, and in term infants, the rate is reduced to about 60%. One of the most effective and low-risk ways to treat neonatal jaundice is the use of light therapy or phototherapy. Fluorescent lamps, tungsten halogen lamps, LEDs, optical fibers and etc are used in these devices. Bilirubin reacts to green light and blue light. The green light's wavelength is in the range of 570-495 nm. The blue light has a wavelength of 495-450 nm and an absorption range of 450 nm. Studies have found that the best light for phototherapy devices is a light that has the wavelength of 400 to 520 nm, and because the blue light absorption rate is about 450 nm, so it is used in phototherapy. In addition to its proper absorption rate, it also has antimicrobial activity against bacteria. It is difficult to determine the exact duration of the phototherapy, because each infant has his/her specific conditions and the exact duration cannot be determined generally. Phototherapy should be continued until the bilirubin level in the baby's blood is sufficiently reduced, monitored by the supervision, and does not pose a threat to the baby. Phototherapy devices have different types, each with advantages over their predecessors. In existing models, because of their unique features like high sensitivity to bilirubin reduction, higher power, and efficiency, lighter, lower heat generation, lower cost and longer life devices, LED light sources are widely used in phototherapy devices. According to all the studies, we are looking for a device with proper coverage, portability, and moving the baby with the device without separating the baby from the baby as well as providing a quiet space for the mother and baby away from the hospital environment.

Tunable light emission using crystalline carbon dots

Carbon quantum dots (CQDs) with an approximate size of 8 nm were prepared by a simple and cost-effective green technique—pyrolysis of cotton. Synthesized CQDs exhibit broad fluorescence covering almost blue and green light wavelengths. They show low cytotoxicity and good photostability. A simple mixing of rhodamine 6G chloride with highly fluorescent carbon dots in water led to aggregation of dye molecules on carbon dot surface. Controlling the emission of free rhodamine 6G dye with that of the resultant carbon dot-aggregated rhodamine 6G composite resulted in efficient white light emission with the CIE coordinate (0.305, 0.313). Suitable mixture of blue-light-emitting CQD in aqueous solution and rhodamine 6G dye can potentially be applied for tunable white light emission.

Research progress of efficient green perovskite light emitting diodes

Perovskite light emitting diodes exhibit the advantages of high color purity, tunable wavelength and low producing cost. Considering these superiorities, one regards perovskite light emitting diodes as very promising candidates for solid state lighting and panel displaying. Human eyes are very sensitive to green light, thus green perovskite light emitting diodes receive the most attention from researchers. Since the advent of the very first green perovskite light emitting diode, the external quantum efficiency has climbed from only 0.1% to over 20%. In this review, we mainly discuss the history of green perovskite light emitting diodes, the basic concepts of perovskite materials and green perovskite light emitting diodes, and the common methods to improve the efficiency of green perovskite light emitting diodes. The bandgap of bromide perovskite is about 2.3 eV, which is located just on a green light wavelength scale and thus becomes the suitable emitting layer material for green emission. There are mainly two types of device structures, i.e. regular format and inverted format. The whole working process of green perovskite light emitting diodes can be divided into two stages, i.e. the injection and recombination of charge carriers. One engineers the energy levels of different layers to improve the injection of charge carriers. They also raise up the strategy so-called surface passivation to reduce the defect density at the interface in order to avoid the quenching phenomenon. One usually inserts a buffering layer to realize the surface passivation. Besides, perovskites possess very small exciton binding energy, which is at the same order of magnitudes as the kinetic energy at room temperature. Charge carriers become free in this case, which will severely reduce the radiation recombination probability due to the non-radiation recombination process such as Shockley-Read-Hall effect and Auger recombination. To solve the problem, people fabricate three types of perovskites, namely quasi two-dimensional perovskite, perovskite quantum dot, and perovskite nanocrystal. In this way, the charge carriers can be confined into a limited space and the exciton binding energy will hence be improved. From the efficiency perspective, the green perovskite light emitting diodes promise to be commercialized. However, another critical issue impeding the development of green perovskite light emitting diodes is the stability problem. Comparing with the organic light emitting diodes and inorganic quantum dot light emitting diodes, the lifetime of perovskite light emitting diodes is too limited, which is only approximately one hundred hours under normal conditions. The temperature, moisture and light exposure are all factors that influence the stability of perovskite light emitting diodes.

Assessment and Optimization of the Circadian Performance of Smartphone-Based Virtual Reality Displays

The non-visual effects of blue light in displays mean that excessive use of smartphones can disturb the human circadian rhythm. Thus, the impact of virtual reality (VR) headsets, which are worn closer to the human eye, may be even more serious. In this paper, based on non-visual parameters, such as the circadian action factor (CAF) and circadian illuminance, the circadian performance of smartphone-based VR displays is quantitatively evaluated by an evaluation system we designed. Moreover, we investigate the improvements in the circadian performance of VR headsets resulting from three practical methods for reducing the blue light content. Finally, a theoretical method of shifting the green-light wavelength of the screen close to 555 nm to optimize the CAF of VR headsets is proposed. Overall, the results of this paper are of significant value in quantifying the effects of VR displays on circadian rhythms and improving the safety of VR headsets with regard to human health.

Effects of green wavelength light on antioxidant and non-specific immune responses of the olive flounder Paralichthys olivaceus maintained at different stocking densities

In the present study, we investigated the effects of green light illumination on antioxidant systems and immunity in the olive flounder Paralichthys olivaceus. Fish at three different stocking densities (900, 1350, and 2250 fish per 8-ton tank) were compared. The effects of green light illumination were assessed by measuring survival rates, mRNA expression activity of antioxidant enzymes (superoxide dismutase and catalase), an oxidative stress-related parameter (hydrogen peroxide, H2O2), and immune-related parameters (lysozyme and melatonin). Overall, fish survival rates decreased over the 30-day period of the experiment, but survival rates were significantly higher among the groups of fish exposed to green light. In high stocking densities groups, mRNA levels and activities of antioxidant enzymes and H2O2 concentrations had increased at 30 days; however, in fish under green light conditions, significantly lower levels of antioxidant enzyme expression were observed. By contrast, parameters indicating immune responses decreased in high stocking densities groups, although in fish under green light treatment, significantly higher levels of immune response were observed. A comet assay revealed that a high stocking density increased the rate of nuclear DNA damage; however, treatment with green wavelength light reduced the frequency of damage. These results indicate that although high density induces oxidative stress and reduces immune system responses in olive flounder, green wavelength light prevents oxidative stress and boosts the immune system.

Autofluorescence study and selected cyanidin quantification in the Jewel orchids Anoectochilus sp. and Ludisia discolor.

Anoectochilus sp. and Ludisia discolor are known as Jewel orchids. Both species are terrestrial wild orchids that grow in shaded areas of forests. The Jewel orchids are renowned for the beauty of their leaves, which are dark-green laced with silvery or golden veins. The orchids are used as a cure in various parts of Asia. Overharvesting and anthropogenic disturbances threaten the existence of the Jewel orchids in the wild, necessitating human intervention in their survival. An understanding of the structure and adaptations of a plant may assist in its survival when propagated outside of its habitat. In this study, ex vitro leaves of Anoectochilus sp. and L. discolor were subjected to freehand sectioning, and then inspected through brightfield and fluorescence microscopy. The study indicated that all parts of both plants presented typical monocotyledonous characteristics except the leaves. The leaves displayed dorsiventrality with distinct palisade and spongy mesophyll layers. The spongy mesophyll layer contained cells which fluoresced a bright red when exposed to ultraviolet, blue, and green light wavelengths, hinting at the presence of anthocyanins for photoprotection. Cyanidin was detected in the leaves of L. discolor, as enumerated through high performance liquid chromatography (HPLC). The observations indicated that Anoectochilus sp. and L. discolor are well-adapted to live under shaded conditions with minimal exposure to light.

Effects of recombinant vertebrate ancient long opsin on reproduction in goldfish, Carassius auratus: profiling green-wavelength light.

This study was conducted to identify the possible effect of recombinant vertebrate ancient long (VAL) opsin as a non-visual "photoreceptor" in the deep brain of goldfish, Carassius auratus. In addition, we investigated the effects of green-wavelength light on the predictable reproductive function of VAL-opsin as a green-sensitive pigment in the deep brain. To determine this, we quantified changes in gonadotropin hormone (GTH) [GTHα, follicle stimulating hormone (FSH) and luteinizing hormone (LH)] and estrogen receptor (ER; ERα and ERβ) mRNA expression levels associated with goldfish reproduction as well as changes in plasma FSH, LH, and 17β-estradiol (E2) activities after injection of recombinant VAL-opsin protein in two concentrations (0.1 or 0.5μg/g body mass) for 4weeks (injection once weekly) and examined the possible impact of green-wavelength light (500, 520, and 540nm) on the function of VAL-opsin. As a result, all parameters associated with reproduction significantly increased with time and light-emitting diode (LED) exposure. Based on these results, we suggested that VAL-opsin in the deep brain is involved in goldfish maturation, and it is possible that green-wavelength light improves the ability of VAL-opsin to promote maturation by increasing VAL-opsin expression.