Light Flux Research Articles

Comparative optical performance investigation of Cross Compound Parabolic Concentrators designed with the elimination of multiple reflections principle

This paper evaluates low-profile solar concentrators with low-material consumption that improve the optical performance of Crossed-Compound-Parabolic-Concentrators (CCPCs) by using Eliminating-Multiple-Reflections (EMR). Three CCPC designs, LEMR, HEMR, and hybrid, were analysed using Monte-Carlo ray tracing, with optical efficiency and light flux uniformity as primary metrics. The LEMR and HEMR CCPCs achieved almost 88% average optical efficiency at the outlet aperture within the half acceptance angle. At the BCP, the LEMR CCPC attained an average efficiency of 85.7%, while the HEMR CCPC achieved an average efficiency of 85%. The hybrid CCPC achieved an average optical efficiency of 80% and 86% when the incidence angle was varied in the XY and YZ planes. The results showed that the non-uniformity of the light flux at the BCP remained low compared to the outlet aperture with changes in the incidence angle. A material consumption analysis revealed that the LEMR CCPC has the lowest material consumption as compared to the HMR and hybrid CCPCs and has a more uniform irradiance flux at the BCP. The LEMR CCPC has a relatively lower acceptance angle than the HEMR CCPC, making it suitable for a tracking system with a higher concentration ratio. The HEMR CCPC, on the other hand, can be used as a stationary concentrator due to its larger acceptance angle with a lower concentration ratio and can be applied in rooftops and building-integrated photovoltaics. Similarly, the hybrid CCPC has two different ranges of acceptance angles, making it advantageous for use in rooftops and building-integrated photovoltaics with seasonal tracking.

Sediment CO2 Flux from a Mangrove in Southern China: Is It Controlled by Spatiotemporal, Biotic or Physical Factors?

Carbon gas flux is important for studies on carbon dynamics in mangroves, but the controlling factors have not always been sufficiently understood. In this study, it is suggested that sediment carbon dioxide (CO2) fluxes in a natural mangrove in Southern China are controlled by tidal positions, seasons, species, the densities of crab burrows and pneumatophores, light conditions and sediment temperature. All these factors account for 51.47% variation in CO2 flux from the sediment–air interface. CO2 flux generally decreased along the tidal position from landward to seaward, and was higher in the dry season than in the wet season. CO2 flux was highest in Avicennia marina (grey mangrove) in comparison with Aegiceras corniculatum (river mangrove) and Kandelia obovata. Pneumatophores and crab burrows promoted sediment CO2 flux in the mangrove at a rate of 18.29 and 15.52 mmol m−2 d−1. Dark flux was higher than light flux. Sediment temperature has a negative influence on CO2 flux. Pneumatophores explain the most variation (13.9%) in CO2 flux among the above factors. Our study suggests that the photosynthesis activity of microphytobenthos is an important factor driving the change of CO2 emissions in this natural mangrove. This is of great significance for the study and for the full exploitation of the carbon sink potential of mangroves.

Current State and Prospects for Development of Head Lighting for Vehicles. Part 2. Advanced Designs for Vehicle Headlights

As it has been shown in part 1 of this paper, modern head lighting, due to objective design flaws, does not always meet the requirements of existing international standards, which means a decrease in road safety. To eliminate the previously Multibeam type. These types of headlights are currently either undergoing the stage of production tests or are used in extremely limited batches of vehicles in terms of the number of produced units. According with the results of this analysis, recommendations have been formulated for the design of advanced head lighting. The main of these recommendations is the use of single high-power LEDs with total internal reflection reflectors, which will provide a sharp cut-off border with efficient use of the source light flux. To increase the resistance of the headlight to temperature rise, it is proposed to use LEDs or other economical light sources together with phosphor parts. It is shown that adaptability is a useful but optional property of vehicle headlights, since it leads to complicate the design, and this is not always justified. The advantages of the headlight, created taking into account the above recommendations, are described, the main of which are the simplification of its design, reduction in weight and improvement of the thermal parameters of the product.

Photometric properties of piles of glass plates: retrospective.

Stacked glass plates have discreetly accompanied the understanding of light since the origins of modern optics. They were studied by Bouguer, Lambert, Brewster, Arago, Stokes, Rayleigh, and many others, whose successive works progressively refined the predictive formulas of the reflectance and transmittance of piles of glass plates as a function of the number of plates and the angle of incidence by considering the decay of light flux by absorption, the multiple reflections between plates, the change in the degrees of polarization, and the possible interferential effects. Through this history of ideas about the optical properties of piles of glass plates, up to the mathematical formalisms from only a few years ago, we show that these successive works, and their subsequent errors and corrections, are inseparable from the evolution of the quality of the glass available each time, in particular its absorptance and its transparency, which strongly influence the quantities and the degree of polarization of the reflected and transmitted beams.

Research on advancing chromatic reproduction and luminosity of a WLED using triple-layer remote phosphor arrangement

In this study, the use of triple-sheet phosphor arrangement (TRP) in performing significant improvements to both color quality and luminous flux of white light emitting diode (WLEDs) is introduced. The phosphor layer of CaLaB3O7:Ce3+,Mn2+ is to accomplish green-spectra enhancement for the boost of luminous efficacy (LE), while MgB2O4:Mn2+ red phosphor layer is for red-spectra enhancement to better color rendering index (CRI) of WLEDs. The changes in these two phosphors’ concentrations present considerable effects on the yellow phosphor YAG:Ce3+ concentration, the color quality scale (CQS), CRI, and LE. Findings display the decrease of YAG:Ce3+ concentration accompanying the increase of red and green phosphor concentrations, for the stabilized average correlated color temperatures (ACCTs) between 6000 and 8500 K. Results also reveal that greater content of MgB2O4:Mn2+ leads to greater CRI value. Meanwhile using the increasing CaLaB3O7:Ce3+,Mn2+ concentration, the CRI lowers considerably. CQS, on the other hand, can increase with CaLaB3O7:Ce3+,Mn2+ concentration from 10% to 14%. Especially, given the enhancement for the CRI as well as CQS, LE value will surge to more than 40% due to the reduction of scattering light and the addition of green light. The outcome of the study is a priceless reference for light emitting diode (LED) producers.

Passive atomic-scale optical sensors for mapping light flux in ultra-small cavities

Understanding light propagation and attenuation in cavities is limited by lack of applicable light sensing technologies. Here we demonstrate the use of light-sensitive metastable states in wide bandgap aluminosilicates (feldspar) as passive optical sensors for high-resolution mapping of light flux. We develop non-destructive, infrared photoluminescence (IRPL) imaging of trapped electrons in cracks as thin as 50 µm width to determine the spatio-temporal evolution of light sensitive metastable states in response to light exposure. Modelling of these data yields estimates of relative light flux at different depths along the crack surfaces. Contrary to expectation, the measured light flux does not scale with the crack width, and it is independent of crack orientation suggesting the dominance of diffused light propagation within the cracks. This work paves way for understanding of how light attenuates in the minutest of cavities for applications in areas as diverse as geomorphology, biology/ecology and civil engineering.

Surface Modification of Nickel Oxide (II) Thin Films Obtained by Gas-Phase Deposition

The technology of producing stable electrochromic anode nanocomposite thin film coatings based on nickel oxide (II) has been developed, which are used as active layers for modulating light flux in the manufacture of various technical devices. The method involves introduction of carbon nanoparticles (carbon-containing particles) into outer layers of nickel oxide (II) thin films obtained by gas-phase deposition under conditions of cathodic polarization in potentiostatic mode in aqueous media containing water-soluble hydroxylated fullerene derivatives - fullerenol С60(ОН)24, without change of their optical density in the initial state. The technology of the method realization allows to effectively change electrochromic properties of nickel oxide (II) thin films and to obtain a nanocomposite, which is a matrix of a thin layer of nickel oxide (II), doped with carbon nanoparticles, with increased contrast and having the ability to maintain a colored state after switching off polarization under open chain conditions for a long time without energy consumption in solution and in air, i.e., characterized by an “optical memory effect”.

Coplanar Capillary Plasma Electrode Discharge Flat-Panel Lamps Based on Porous Anodic Alumina

A coplanar capillary plasma electrode discharge is a promising source owing to its superior performance. In this study, a coplanar capillary plasma electrode discharge flat-panel plasma lamp fabricated from porous anodic alumina and glass was designed to investigate its properties. Coplanar capillary plasma electrode discharge flat-panel lamps with porous anodic alumina dielectric layers were fabricated and investigated. Changing of the frequency and voltage of the power supply and altering of the thickness of the dielectric layers and the interval distance of the electrode were carried out to optimize the performance of the lamps by decreasing the spark-ignition voltage and enhancing the luminous efficacy. The luminance can exceed 7200 Cd/m2 and the white light flux efficacy is more than 4.92 lm/W. The discharge process of capillary plasma electrode discharge was modeled and simulated using COMSOL Multiphysics. The electron density and temperature were also analyzed. The results show that small plasma jets were produced at the pores of the porous anodic alumina, which helped stabilize the plasma. The voltage in the gas gap changes sharply with the geometry of the porous anodic alumina dielectric layer, leading to a higher electric field. The spark-ignition voltage decreased. Small plasma jets increase the plasma uniformity. The electron density and electron temperature reach approximately 1.94 × 108 m3 and 3.34 eV, respectively. A high electric field intensity produced at the porous anodic alumina validated the promising potential in related fields.

A Simple and Reliable Method to Determine Mean Incident Light Flux Densities on Cylindrical Photoreactors and Photobioreactors from a Unique Fluence Rate Measurement

A new method to determine the hemispherical incident light (photon) flux density onto cylindrical photoreactors or photobioreactors is presented. It applies to situations where the photo(bio)reactor is radially illuminated by surrounding artificial sources or solar light. It relies on the direct measurement of a fluence rate with a spherical sensor put at the center of the reactor. Theoretical relations leading to the calculation of the hemispherical incident light flux density from the fluence rate value are established, and a web application performing those calculations is made available. It relies on a view factor, the expression of which, established for the first time with any assumption of the angular distribution of light at the boundary, is given. This requires a proper definition of the degree of collimation for the incident radiation field. Two different and complementary experimental devices are used to validate the method. As a result, the proposed method appears to be simple and reliable; it even looks faster and more accurate than actinometry for this particular geometry.

Design and application of a novel direct light-driven thermogravimetric analyzer

Thermogravimetric analysis is one of the evaluation means widely used to characterize thermoinduced chemical reaction and mass variation processes. However, the emergence of photothermal characteristics research makes traditional thermogravimetric analysis unable to meet the requirements. Therefore, a novel direct light-driven thermogravimetric analyzer is designed for fast photothermal integrated pyrolysis weight loss measurement based on the principle of high temperature measurement under light flux. The photothermal conversion characteristics are studied by analyzing the calcination progress of the blackened calcium carbonate particles. At the same time, the error and uncertainty analysis of the instrument is carried out. Compared with the conventional thermogravimetric electric heating approach, the direct light-driven thermogravimeter provides the same environment as the actual solar photothermal capture and utilization scenarios and enables getting deep insights into the mechanism of the photothermal conversion and chemical reaction kinetics involved which are consistent with the real solar-thermal energy applications. Its unique photothermal integrated design is also valuable for the composition analysis, kinetic analysis or evaluation of solid-gas balance of the materials, which provides an important analysis method for solar photothermal conversion.

Detection of Exoplanets based on the Transit Method

Exoplanets are planets orbiting a star other than the Sun. These exoplanets may exist in many different forms, such as a hot Jupiter and super earth. Detecting is the first step to further studying the properties of these exoplanets. In this paper, based on data of star Qatar-1 gathered from July 22nd 2022, a light flux curve is developed during the period of 04:28 - 07:01 UTC through which the star is observed. The presence of an exoplanet, presumably Qatar-1b, is revealed in the analyzing results of the collected data, showing the validity of the transit approach for exoplanet detection. By using this approach, exoplanets planets can be discovered for further research in regards to potentially habitable and/or resource-rich exoplanets.

For improvements in chromatic scales and luminescent fluxes of white lights: developing a dual-layer remote phosphor structure

This study compares red-phosphor LaOF:Eu 3+ impacts on a single-film remote phosphor configuration (SRPC) and a double-film remote phosphor configuration (DRPC). Mie theory is used to demonstrate the relationship between light flux and color quality. SRPC is a phosphor layer consisting of LaOF:Eu 3+ particles mixed with YAG:Ce 3+ . Meanwhile, DRPC is two separate films of red and yellow phosphors. To increase scattering properties, we added 5% SiO 2 into phosphor layers. The differences in structure affect significantly white light emitting diodes’ (WLEDs’) optical properties. Attained figures and statistics show that the color rendering indices (CRIs) increase along with the concentrations of both structures, and these numbers are approximately similar. However, DPRC exhibits a color quality scale (CQS) of 74 in all examined chromatic temperatures (5600 K - 8500 K), which is greater than SRPC’s 71 at 8500 K. Besides, the luminous efficiencies (LEs) in DRPC are more outstanding than that of SRPC, at given LaOF:Eu 3+ concentration percentages (2%-14%). To summarize, DRPC offers greater benefits in luminous flux and color quality, compared to SRPC. Choosing the proper red light phosphor concentration, on the other hand, becomes a crucial aspect of achieving the ideal CQS and LEs.

Mammalian Cornea Inspired Anti‐Fogging Silica Glass Surface Achieved by Femtosecond Laser

AbstractFog generation can severely damage optical systems by degrading the light absorption rate and imaging quality of optical components. Furthermore, fog can reduce the light flux and transmittance of the optical system, resulting in poor imaging clarity and contrast. Studies have focused on minimizing fog formation and effects. Drawbacks such as high energy consumption and waste pollution severely limit the application of conventional methods. However, achieving high fog resistance of optical components remains a challenge. A novel method of fabricating anti‐fogging slippery surfaces (inspired by the anti‐fog mechanism of the mammalian cornea) on silica glass by using femtosecond lasers is proposed to achieve durable and environment‐friendly optical devices that can achieve anti‐fogging in real time. The femtosecond laser wet etching method is used to fabricate the inside cabin of glass. The cabin filled with graphene spontaneously heats the sample under sunlight to prevent fog formation. In addition to exhibiting excellent anti‐fogging characteristics, the prepared sample achieves high optical transmittance, high durability, and excellent self‐repair capability. Thus, the proposed method exhibits considerable potential for application in numerous domains.

Optoelectronic Device for Measuring Radio Signal Samples and Evaluating Its Accuracy Characteristics

When using quadrature signals in radio channels, flat and selective fading, multipath radio reception, intersymbol interference, and jitter occur. In addition to the need to accurately estimate the value of the phase difference at the current and previous clock intervals, a critical factor in receiving and demodulating such signals is the accuracy of measuring the amplitude of their samples. When demodulating such signals, an approach is possible, the basis of which is to measure the values of individual signal samples at discrete time points with higher accuracy than in existing electronic devices. Such an approach can be implemented by an optoelectronic device in which a coherent luminous flux is formed, the parameters of which are modulated by a voltage proportional to the readings of the received radio signal. Using a modulated light flux, an interferogram is formed, the parameters of which are directly related to the parameters of this light flux and accordingly to the parameters of the received radio signal. This makes it possible, by increasing the accuracy of estimating radio signal samples, to increase the base of the alphabet used for code manipulation, the efficiency of using the allocated frequency band for transmitting information and reduce the probability of a bit error. The article presents a mathematical model for converting the parameters of the received radio signal into the parameters of the generated interferogram. By mathematical modeling the accuracy characteristics of an optoelectronic device for measuring radio signal samples were evaluated. The results of mathematical modeling illustrating the relationship of the parameters of the optical elements of the device with the accuracy of estimates of the radio signal counts are presented. The practical significance of the proposed optoelectronic device can be used as an independent device for analog-to-digital conversion of radio signals, as well as part of demodulators for QAM and OFDM signals in networks and communication systems of 5G and the next generations.

Simulation of TAZ:Ir(ppy)3-BCP/ZnO heterostructure OLED

In this article, we report the temperature dependent I-V characteristics of TAZ:Ir(ppy)3-BCP/ZnO heterostructure based OLED. In addition, we have also optimized the thickness of the ETL (electron transport layer) of the designed OLED. For the optimized ETL (ZnO layer) we have simulated the I-V characteristics, Voltage vs light flux curves and current density vs light flux curves. From such simulation study, it has been found that the designed OLED can work properly at the room temperature with the operating voltage ∼ 4.25 V. Further, the optimized ETL thickness in the TAZ:Ir(ppy)3-BCP/ZnO heterostructure based OLED should be 50 or 60 nm for proper operation and for getting the noticeable light flux.

Исследование параметров микроэлектромеханических систем дефлекторов для определения магнитной проницаемости материала диполей

Micro-electromechanical (MEMS) deflectors with electromagnetic control and an experimental stand for measuring their functional parameters are considered. The electromagnetic control method makes it possible to obtain a high positioning accuracy of the reflected beam along one spatial coordinate, and also provides increased speed with the time of deviation of the light flux to a predetermined position of 5–10 μs. Graphs of experimental and theoretical dependences of the angle of deviation of the light flux on the induction of the control magnetic field of MEMS deflectors are presented. Using the method of successive approximations, the value of the magnetic permeability of the dipole material µ = 120 was selected, and the maximum value of the angular deviation of the light flux along one spatial coordinate was determined, which is 13.50. The MEMS presented in this paper can be used, first of all, as high-speed deflectors and optical flow scanners with a beam diameter of up to 2.5 mm.

Influence of luminance modeses on the metamorphosis of artemia in aquaculture

The article presents the results of studies of the influence of luminance modes on ontogenesis of artemia cultivated in artificial conditions in a closed cycle. The aim of the work was to study the effect of light on morphological features of artemia at different stages of ontogenesis. During the work, the luminance modes of 1.5 kl, 2.5 kl and 4 kl were used. It was found that the intensity of the light flux differently affects the ontogenesis and development of individual parts of the body of artemia. In one case, during the cultivation of artemia, optimal results were obtained at 2.5 klx, in the other at 4 klx. The luminance mode of 1.5 klx, turned out to be the least effective. Observations of the growth and development of Artemis larvae in an artificial environment revealed that the luminance mode of 4 klx had a more noticeable stimulating effect on the length of the body, abdomen, cephalothorax and furca than the mode of 2.5 klx at the initial stages of postembryonic development of larvae during the first 120 hours. When cultivating sexually mature artemia, as the results of studies have shown, the luminance mode - 2.5 klx had a more pronounced effect on body length, abdominal length, cephalothorax length, abdominal width and the number of bristles on the furc than the 4klx mode. For the first time, the results of morphological studies demonstrating the effect of light intensity on the development of individual parts of the body of crustaceans in aquaculture have been obtained. The study was supported by the Development Program of the Saratov state university of genetics, biotechnology and engineering named after N.I. Vavilov (Prioritet -2030).

Reasonable use of Indoor Lighting in Human Living Environment

In today's life, lighting design has become a very important part of the indoor environment, affecting not only the presentation of the design, but also human health. In current lighting designs, there is still a lack of attention to the use of lighting, resulting in visual and health discomfort for occupants. Based on the original light research, this paper analyzes and applies the light to explore the most scientific direction of light use. Analysis of color temperature, light flux, illumination, and other data of lighting types on the market, and investigation of the effect on human perception. The types of lighting should also not be harmful to the eye and safe to use for long periods of time. Reflective materials are another alternative method to reflect natural lighting to the room to bring spaciousness when there is no available natural lighting directly. In the future, there should be experimental lighting that may mimic or replace lighting in nature, or lighting that is fully adapted to the user's senses, emotions, and fatigue. This paper looks forward to finding more appropriate ways to use interior lighting and is dedicated to addressing unreasonable lighting designs in interior design.

Enhanced photocatalytic performance of NiFe2O4 nanoparticle spinel for hydrogen production

The spinel NiFe2O4, prepared from nitrates precursors, was characterized by thermal analyses, X-Ray Diffraction, UV-Vis diffuse reflectance, Scanning electron microscopy, X-Ray Fluorescence spectrometry, X-ray photoelectron spectroscopy and photo-electrochemistry measurements. The X-ray diffrcation analysis of the powder indicates a cubic phase with a lattice constant of 8.327(8) Å and crystallite size of 19 nm. The X-Ray Fluorescence spectrometry indicates a stoichiometry, very close to NiFe2O4 catalyst calcined at 900 °C The X-ray photoelectron spectroscopy analysis confirmed the valences and crystallographic sites of the transition elements. The direct optical gap of NiFe2O4 (1.78 eV), due to the crystal field splitting of the 3d orbital in the octahedral site, is well suited for the solar spectrum and attractive for photo-electrochemical H2 production. The flat band potential (Efb = 0.47 VSCE) was obtained from the capacitance-potential (C−2 - E) characteristic in NaOH (0.1 M) electrolyte. A conduction band of −1.11 VSCE, more cathodic than the H2 level (−0.8 VSCE), enabled the use of NiFe2O4 for the water reduction into hydrogen. The H2 evolution rate of 46.5 μmol g−1 min−1 was obtained under optimal conditions (1 mg of catalyst/mL, NaOH and 50 °C) in the presence of SO32− (10−3 M) as hole scavenger under visible light flux of 23 mW cm−2. A deactivation effect of only 1% was obtained.

Diffuse optical properties of a Fresnel lens sunlight concentrator.

A combined module that combines a concentrator with planar photovoltaic circuits provides energy conversion of both parts of global terrestrial radiation: direct sunlight by concentrator solar cells and scattered (diffuse) sunlight by planar (non-concentrator) photoconverters. The decrease in Fresnel lens concentrating ability is usually associated with imperfections in the optical refractive surfaces, where some part of the direct light, which arrives normal to the surface of the Fresnel lens and is intended to be concentrated, becomes scattered and directed off the highly efficient concentrator solar cell. The diffuse light flux propagates inside the volume of the combined photovoltaic module. This flux undergoes multiple reflections from the structural elements, is partially absorbed, and ultimately reaches the photoconverters of the planar circuit. Thus, two types of diffuse light impinge the planar circuit: "external" from the atmosphere and "internal" produced by the Fresnel lens from direct light. This Letter proposes a method for determining the diffuse properties of sunlight concentrators such as Fresnel lens.