Distribution Of Incident Light Research Articles

Enhancing plant growth and yield in dragon fruit (Hylocereus undatus) through strategic pruning: A comprehensive approach for sunburn and disease management

Effective canopy management in fruit crops is imperative for development of an ideal plant framework which facilitates uniform distribution of incident light, air circulation, thus to improve microclimate. This sustains photosynthesis and reduces spread of pest-diseases, addresses competition among fruits to achieve high productivity. This study aims to assess the impact of canopy management through strategic pruning on growth, physiological and biochemical changes, flowering, fruiting and incidence of sunburn and diseases in dragon fruit. The results indicated improvement in chlorophyll content and NDVI in pruned canopy. Pruning not only increased production of new sprouts but also fruitful cladodes compare to un-pruned plants. Canopy treatments significantly reduced sunburn by 67.68 % and 69.05 % in 2022 and 2023, whereas disease incidence was minimized by 43.23 and 81.51 %, respectively over control. Compared to first year, lightly and moderately pruned plants shown yield increment of 11 to 48 % during second year reaching at non-significant level to yield in control, where yield increment was just 2.8 %. Cladode numbers were positively correlated with sunburn, diseases, fruit yield and negatively correlated with sprouting and fruitful cladodes. Therefore, it is advisable to maintain 120-160 cladodes or 12 to 14 cladodes per square meter in mop-top training system through need based light pruning in semi-arid regions.

The influences of light scattering on digital light processing high-resolution ceramic additive manufacturing

Digital light processing (DLP) has emerged as a highly promising 3D printing technology, which is due to its ability to fabricate components and structures with low cost and high precision. The DLP is, therefore, applicable in a wide range of fields. The phenomenon of light-scattering plays a dominant role in the DLP manufacturing process, but the specific impact of ceramic particles on the distribution of incident light remains unclear. The present study has, therefore, focused on studying the effect of ceramic particles on light-scattering by performing extensive theoretical finite element simulations. The aim was then to improve the curing quality of the DLP 3D printing process. More specifically, spherically shaped particles with a uniform distribution, lower duty ratios, or materials with lower refractive indices were necessary conditions for enhancing the printing precision due to the mitigated lateral light scattering effects. The overall results of this study have provided valuable guidance for the control of the light-induced curing in the 3D printing process of ceramics, thereby facilitating advancements in ceramic-based fabrication techniques.

Brewster differential microscopy

Imaging of transparent samples such as cells is important in the biomedicine field; however, insignificant absorption and weakly scattering limit the imaging contrast of phase objects. Here, we propose and demonstrate Brewster differential microscopy based on simple optical reflection at the glass interface. The combination of spin–orbit interaction of light and the Brewster effect can perform two-dimensional differentiation to the incident light distribution and, thus, achieves isotropic edge-enhanced imaging of pure phase objects, which overcomes the limitation of traditional one-dimensional imaging. Furthermore, by introducing bias retardation, we also reconstruct the original phase distribution. The proposed microscopic imaging mechanism does not involve any complex modulation devices and takes advantages of simple and low-cost structure. The results indicate that our research shows promising applications for nondestructive imaging of biological cells.

Efficient Inverse Design of Large-Area Metasurfaces for Incoherent Light

Incoherent light is ubiquitous, yet designing optical devices that can handle its random nature is very challenging, since directly averaging over many incoherent incident beams can require a huge number of scattering calculations. We show how to instead solve this problem with a reciprocity technique which leads to three orders of magnitude speedup: one Maxwell solve (using any numerical technique) instead of thousands. This improvement enables us to perform efficient inverse design, large scale optimization of the metasurface for applications such as light collimators and concentrators. We show the impact of the angular distribution of incident light on the resulting performance, and show especially promising designs for the case of "annular" beams distributed only over nonzero angles.

Study on scattering light field distribution of optical element in-surface defects based on Mueller matrix

For precise optical elements, the size of in-surface defects is at the nanometer scale. When incident light illuminates in-surface defects on optical elements, strong diffraction and scattering effects are produced, and this greatly reduces the beam quality in optical systems. In this study, a three-dimensional model of the in-surface defects of K9 optical components was established. On this basis, a theoretical model of electromagnetic scattering between the defect and the incident and scattering fields was constructed. The 4 × 4-order scattering Mueller matrix light field distributions of incident light modulated by different-sized defects were obtained by numerical simulations, and the influencing factors were analyzed. These simulations provide a theoretical basis and a reference for the manufacture of precision optical elements and a scale calibration for surface quality detection methods.

Uniform and Gaussian Ultraviolet Light Intensity Distribution on Droplet for Selective Area Deposition of Particles

Abstract Particle transport through Marangoni convection inside a sessile droplet can be controlled by the ultraviolet (UV) light distribution on the surface. The photosensitive solution changes the surface tension gradient on the droplet surface and can induce clockwise and counterclockwise circulations depending on the incident light distribution. In this paper, the stream function in the sessile drop has been evaluated in toroidal coordinates by solving the biharmonic equation. Multiple primary clockwise and counterclockwise circulations are observed in the droplet under various concentric UV light profiles. The downward dividing streamlines are expected to deposit the particles on the substrate, thus matching the number of deposited rings on the substrate with the number of UV light rings. Moffatt eddies appear near the contact line or centerline of the droplet depending on the UV light profile and its distance from the contact line.

Ag@SiO<sub>2</sub> coupled structure’s design and regulation and control of response to thin film solar cells

The coupled nano-structure Ag@SiO<sub>2</sub> has both plasmon excitation like metallic nanoparticles and diffraction scattering like a dielectric nanosphere, which effectively controls the propagation path and the energy distribution of incident light and shows great potential applications in light trapping for thin film solar cells. In this work, we construct a three-dimensional electromagnetic model based on the finite-difference time-domain (FDTD) and rigorous coupled-wave analysis (RCWA) method to investigate the regulation mechanism of Ag@SiO<sub>2</sub> coupling structure to the spectral response of amorphous silicon cells. By being optimally designed, a high-efficiency cell device is achieved. The results show that the transmitted light into the active layer reaches a maximum value when Ag and SiO<sub>2</sub> have their feature sizes of 18 and 150 nm, respectively. The absorption spectrum of the corresponding cell device also arrives at its maximum value. The photoelectric conversion efficiency is enhanced from 7.19% to 7.80%, with an increment of 8.48% compared with the flat solar cell with an equivalent thickness of absorbing layer.

Edge collection function: an analytical expression for the optical efficiency of an energy-harvesting device based on photoluminescence

An edge collection function is proposed for characterizing the optical efficiency of an energy-harvesting system that utilizes photoluminescence (PL) in a waveguide. We assume that a single spot in a waveguide is excited and that PL is isotropic. For the photons to be collected by one edge of the waveguide, they must be emitted toward the edge, trapped in the waveguide and they must survive self-absorption on the way. The optical efficiency is formulated as the product of these probabilities. When this function is calculated for every spot on the waveguide and for each wavelength of the PL spectrum, the efficiency of the system is given by superposition. Its validity is checked by a Monte Carlo simulation for the case of no self-absorption loss. In experiment, we fabricate a 5-cm2 waveguide with a thin layer of Lumogen F Red 305 and measure its efficiency by placing a photodiode array in the vicinity of its edge with a small air gap. The formula roughly reproduces the efficiency and its dependency on the position of the excitation spot. This analytical approach allows one to estimate the optical efficiency for an arbitrary incident light distribution with small computational complexity.

Enhancing continuous hydrogen production by photosynthetic bacterial biofilm formation within an alveolar panel photobioreactor

Photofermentative hydrogen production at higher rate is desirable to make the technology of biological hydrogen production in practical application. An easy fabricating alveolar panel photobioreactor with high surface-to-volume ratio was proposed in this study to realize biofilm formation and used for developing a continuous bioprocess of hydrogen production. Effects of key operating parameters, i.e. variation in intensity of incident light, initial concentration of carbon substrate and flow rate on the rate of nitrogenase-based H2 production were investigated using response surface methodology (RSM) with Box-Behnken design. Surface and contour plots of the fitted regression model revealed that optimum H2 production rate of 57.6 mL/h/L was obtained at 125.9 μE/m2/s incident light intensity at 590 nm light wavelength, 52.4 mM initial concentration of carbon substrate and 209 mL/h flow rate. Regular groove surfaces within this photobioreactor were considered to have mutual effects on enhancement of continuous hydrogen production by enriching bacterial cell density, enhancing mass transfer of carbon substrate to facilitate release of protons and electrons, enhancing removal of molecular H2, and uniformly distribution of incident light within the photobioreactor for sufficient conversion into ATPs.

High-fidelity 3D printing using flashing photopolymerization

Photopolymerization-based 3D printing has emerged as a promising technique to fabricate 3D structures. However, during the printing process, polymerized materials such as hydrogels often become highly light-scattering, thus perturbing incident light distribution and thereby deteriorating the final print resolution. To overcome this scattering-induced resolution deterioration, we developed a novel method termed flashing photopolymerization (FPP). Our FPP approach is informed by the fundamental kinetics of photopolymerization reactions, where light exposure is delivered in millisecond-scale ‘flashes’, as opposed to continuous light exposure. During the period of flash exposure, the prepolymer material negligibly scatters light. The material then polymerizes and opacifies in absence of light, therefore the exposure pattern is not perturbed by scattering. Compared to the conventional use of a continuous wave (CW) light source, the FPP fabrication resolution is improved. FPP also shows little dependency on the exposure, thus minimizing trial-and-error type optimization. Using FPP, we demonstrate its use in generating high-fidelity 3D printed constructs.

Nanostructured texturing of CH3NH3PbI3 perovskite thin film on flexible substrate for photodetector application

Large-area nanostructured hybrid CH3NH3PbI3 perovskite thin films are fabricated via a direct one-step blade method on nanograting-patterned flexible cyclic olefin copolymer (COC) substrate in ambient condition. The nanostructure of perovskite films can be well controlled with high crystalline quality, revealed by X-ray diffraction (XRD) and photoluminescence (PL) characterization. Flexible photodetectors with nanostructured perovskite thin films demonstrate better performance than their counterparts with flat perovskite films. Numerical modeling of the local energy distribution of incident light reveals the contribution of nanostructures directly textured in perovskite films to the light absorption enhancement. The blade-coated CH3NH3PbI3 photodetector with the nanostructured texturing exhibits a high detectivity of 1.21 × 109 Jones and a responsivity of 0.36 A/W, which are 15% and 47% higher compared with the photodetector with the flat perovskite film, respectively. Our work offers a facile etching-free process that can create high crystalline nanostructured perovskite films for high-performance photodetectors over large-area flexible substrates.

"Crypto-Display" in Dual-Mode Metasurfaces by Simultaneous Control of Phase and Spectral Responses.

Although conventional metasurfaces have demonstrated many promising functionalities in light control by tailoring either phase or spectral responses of subwavelength structures, simultaneous control of both responses has not been explored yet. Here, we propose a concept of dual-mode metasurfaces that enables simultaneous control of phase and spectral responses for two kinds of operation modes of transmission and reflection, respectively. In the transmission mode, the dual-mode metasurface acts as conventional metasurfaces by tailoring phase distribution of incident light. In the reflection mode, a reflected colored image is produced under white light illumination. We also experimentally demonstrate a crypto-display as one application of the dual-mode metasurface. The crypto-display looks a normal reflective display under white light illumination but generates a hologram that reveals the encrypted phase information under single-wavelength coherent light illumination. Because two operation modes do not affect each other, the crypto-display can have applications in security techniques.

Thermodynamics of Light Extraction from Luminescent Materials

Light extraction from luminescent materials, where luminescence generated in a high refractive index medium must be coupled to a lower index medium, is a complex problem with significant ramifications for efficient LED and phosphor converted LED lighting. We derive thermodynamic arguments which show that light transmission for incident Lambertian light through arbitrary structured or non-structured surfaces is always limited by the ratio of incident to output étendues. Numerical simulations of various strongly scattering surfaces in the wave-optic regime are made to confirm the surface extraction results. The results are also extended to arbitrary angular radiance distributions of incident light as in Lenef, et al. [Opt. Lett., 39, 3058 (2014)], but also generalized to cases of restricted angular output emission. Furthermore, we show how cavity effects and scattering are both needed to overcome the thermodynamic surface extraction limits. Examples of both surface scattering and a converted LED with volume scattering are given. Finally, a derivation of the Lambertian light transmission theorem is developed from scalar wave-optics to highlight the physics of the thermodynamic result and to provide limits of applicability of the surface extraction limit.

Quasiguided modes of opaline photonic crystals covered by Ge2Sb2Te5

The physical origin of resonant Wood's anomalies in the reflection spectra of three-dimensional (3D) opaline photonic crystals covered with ${\mathrm{Ge}}_{2}{\mathrm{Sb}}_{2}{\mathrm{Te}}_{5}$ (GST225) is discussed. For this purpose, the optical reflection spectra are studied for different incident angles of light both experimentally and theoretically. The performed eigenmode analysis reveals that the Wood's anomalies originate from the quasiguided modes which appear in the GST225 capping layer. This conclusion is supported by the simulated electromagnetic near-field distributions of incident light at resonant frequencies. The experimental reflection spectra are in good agreement with theoretical calculations performed by the Fourier modal method in the scattering matrix form.

Selective-area growth of periodic nanopyramid light-emitting diode arrays on GaN/sapphire templates patterned by multiple-exposure colloidal lithography

Gallium nitride-based nanopyramid light-emitting diodes are a promising technology to achieve highly efficient solid-state lighting and beyond. Here, periodic nanopyramid light-emitting diode arrays on gallium nitride/sapphire templates were fabricated by selective-area metalorganic chemical vapor deposition and multiple-exposure colloidal lithography. The electric field intensity distribution of incident light going through polystyrene microspheres and photoresist are simulated using finite-different time-domain method. Nitrogen as the carrier gas and a low V/III ratio (ratio of molar flow rate of group-V to group-III sources) are found to be important in order to form gallium nitride nanopyramid. In addition, a broad yellow emission in photoluminescence and cathodoluminescence spectra were observed. This phenomena showed the potential of nanopyramid light-emitting diodes to realize long wavelength visible emissions.

Photosynthetic performance of two Nannochloropsis spp. under different filtered light spectra

The integration of spectrally selective photovoltaic filters together with microalgae cultivation systems have been previously shown to improve both production efficiency and economics. This means that filtered irradiance incident upon the culture is a portion of the entire solar spectrum. In order to test the viability and optimize such integrated systems, in depth growth and photosynthesis studies of microalgae in such conditions are required. In this applied study, we investigated the impact of spectrally limited light and concomitant reduction in light irradiance on the photosynthetic efficiency of two acclimated Nannochloropsis spp. (MUR 266 & MUR 267) through chlorophyll a fluorescence and oxygen evolution based measurements under laboratory controlled conditions. Results indicated that (i) no similarities were found between both Nannochloropsis spp. in regards of their biomass productivity and photosynthetic performance, (ii) blue light acclimated cultures had remarkably higher concentration of chlorophyll a and accessory pigments over biomass due to the lower irradiance, (iii) when photosynthesis was measured on the basis of chlorophyll a fluorescence (based on number of photons absorbed per chlorophyll) and oxygen evolution (based on chlorophyll a content), pink and white light was most efficient for MUR 266 and MUR 267 respectively. The results of this study clearly indicate that by manipulating the spectral distribution of incident light, photosynthetic efficiency of microalgae can be regulated to optimum levels. The allocation of light spectra (i.e. blue) most efficient for the growth and photosynthesis of the microalgae would allow for the generation of up to 151Wm−2 of electrical energy from the remaining unused spectra of sunlight using highly efficient crystalline silicone solar cells.

Handling multiple materials for exposure of digital forgeries using 2-D lighting environments

The distribution of incident light is an important physics-based cue for exposing image manipulations. If an image has been composed from multiple sources, it is likely that the illumination environments of the spliced objects differ. Johnson and Farid introduced a proof-of-principle algorithm for a forensic comparison of lighting environments. However, this baseline approach suffers from relatively strict assumptions that limit its practical applicability. In this work, we address one of the biggest limitations, namely the need to compute a lighting environment from patches of homogeneous material. To compute a lighting environment from multiple-color surfaces, we propose a method that we call "intrinsic contour estimation" (ICE). ICE is able to integrate reflectances from multiple materials into one lighting environment, as long as surfaces of different materials share at least two similar normal vectors. We validate the proposed method in a controlled ground-truth experiment on two datasets, with light from three different directions. These experiments show that using ICE can improve the median estimation error by almost 50 %, and the mean error by almost 30 %.

High-throughput estimation of incident light, light interception and radiation-use efficiency of thousands of plants in a phenotyping platform.

Light interception and radiation-use efficiency (RUE) are essential components of plant performance. Their genetic dissections require novel high-throughput phenotyping methods. We have developed a suite of methods to evaluate the spatial distribution of incident light, as experienced by hundreds of plants in a glasshouse, by simulating sunbeam trajectories through glasshouse structures every day of the year; the amount of light intercepted by maize (Zea mays) plants via a functional-structural model using three-dimensional (3D) reconstructions of each plant placed in a virtual scene reproducing the canopy in the glasshouse; and RUE, as the ratio of plant biomass to intercepted light. The spatial variation of direct and diffuse incident light in the glasshouse (up to 24%) was correctly predicted at the single-plant scale. Light interception largely varied between maize lines that differed in leaf angles (nearly stable between experiments) and area (highly variable between experiments). Estimated RUEs varied between maize lines, but were similar in two experiments with contrasting incident light. They closely correlated with measured gas exchanges. The methods proposed here identified reproducible traits that might be used in further field studies, thereby opening up the way for large-scale genetic analyses of the components of plant performance.

Improvement in the Photocurrent of Inverted Organic Solar Cells Using MoO(x)-Doped TAPC as a P-Type Optical Spacer.

In this work, we demonstrate enhancement in the short-circuit current of inverted organic photovoltaic cells (OPVs) using a p-type optical spacer. The p-type optical spacer, which consists of molybdenum oxide (MoO(x))-doped 1,1-bis[(di-4-tolylamino)phenyl]cyclohexane (TAPC), shows improved transmittance at visible light with high electrical conductivity. The electrical field distribution of incident light at the active layer of OPVs can be controlled by tuning the thickness of the optical spacer in the OPVs. Specifically, the incorporation of the 20-nm optical spacer layer in the OPV leads to enhanced spectral response of the device in the wavelength range of 400-600 nm, which is consistent with the combined results of improved optical absorption and better charge transport characteristics. As a result, the OPV with a 20-nm p-type optical spacer shows improvement in the short-circuit current compared with a device with 10 nm of embedded MoO(x).

Penetration of UV‐visible solar radiation in the global oceans: Insights from ocean color remote sensing

Penetration of solar radiation in the ocean is determined by the attenuation coefficient (Kd(λ)). Following radiative transfer theory, Kd is a function of angular distribution of incident light and water's absorption and backscattering coefficients. Because these optical products are now generated routinely from satellite measurements, it is logical to evolve the empirical Kd to a semianalytical Kd that is not only spectrally flexible, but also the sun‐angle effect is accounted for explicitly. Here, the semianalytical model developed in Lee et al. (2005b) is revised to account for the shift of phase function between molecular and particulate scattering from the short to long wavelengths. Further, using field data collected independently from oligotrophic ocean to coastal waters covering >99% of the Kd range for the global oceans, the semianalytically derived Kd was evaluated and found to agree with measured data within ∼7–26%. The updated processing system was applied to MODIS measurements to reveal the penetration of UVA‐visible radiation in the global oceans, where an empirical procedure to correct Raman effect was also included. The results indicated that the penetration of the blue‐green radiation for most oceanic waters is ∼30–40% deeper than the commonly used euphotic zone depth; and confirmed that at a depth of 50–70 m there is still ∼10% of the surface UVA radiation (at 360 nm) in most oligotrophic waters. The results suggest a necessity to modify or expand the light attenuation product from satellite ocean‐color measurements in order to be more applicable for studies of ocean physics and biogeochemistry.