Search Results (214)

Quantum efficiency (QE) is a critical metric for assessing the performance of industrial digital cameras. The current EMVA1288 standard relies on monochromatic light for QE measurements. Comprehensive QE tests across the visible spectrum often involve elaborate setups and extensive data acquisition. Additionally, such tests may not fully capture camera performance under broadband illumination, which is frequently encountered in industrial applications. This study introduces the concept of average quantum efficiency (AQE) using white light sources and proposes a novel testing method. Systematic experiments and data analyses were performed on two industrial digital cameras under white light sources with different spectral distributions. The results suggest that AQE testing offers a practical and efficient means to evaluate camera performance under broadband illumination, complementing existing monochromatic QE measurement methods. Full article

Photothermal reactions, involving both photochemical and thermal reaction steps, are the most abundant sequences in photochemistry. The derivation of their rate laws is standardized, but the integration of these rate laws has not yet been achieved. Indeed, the field still lacks integrated rate laws for the description of these reactions’ behavior and/or identification of their reaction order. This made difficult a comprehensive account of the photokinetics of photothermal reactions, which created a gap in knowledge. This gap is addressed in the present paper by introducing an unprecedented general model equation capable of mapping out the kinetic traces of such reactions when exposed to light or in the dark. The integrated rate law model equation also applies when the reactive medium is exposed to either monochromatic or polychromatic light irradiation. The validity of the model equation was established against simulated data obtained by a fourth-order Runge–Kutta method. It was then used to describe and quantify several situations of photothermal reactions, such as the effects of initial concentration, spectator molecules, and incident radiation intensity, and the impact of the latter on the photonic yield. The model equation facilitated a general elucidation method to determine the intrinsic reaction parameters (quantum yields and absorptivities of the reactive species) for any photothermal mechanism whose number of species is known. This paper contributes to rationalizing photokinetics along the same general guidelines adopted in chemical kinetics. Full article

When a sample of semiconducting material is illuminated by monochromatic light, in which the photon energy is higher than the energy gap of the semiconductor, part of the absorbed electromagnetic energy is spent on the generation of pairs of quasi-free charge carriers that are bound by Coulomb attraction. Photo-generated pairs diffuse through the material as a whole according to the density gradients established, carrying part of the excitation energy and charge through the semiconducting sample. This energy is indirectly transformed into heat, where the excess negatively charged electron recombines with a positively charged hole and causes additional local heating of the lattice. The dynamic of the photoexcited charge carrier is described by a non-linear partial differential equation of ambipolar diffusion. In moderate doped semiconductors with a low-level injection of charge carriers, ambipolar transport can be reduced to the linear parabolic partial differential equation for the transport of minority carriers. In this paper, we calculated the spectral function of the photoinduced charge carrier distribution based on an approximation of low-level injection. Using the calculated distribution and inverse Laplace transform, the dynamics of recombination photoinduced heat sources at the surfaces of semiconducting samples were studied for pulse optical excitations of very short and very long durations. It was shown that the photoexcited charge carriers affect semiconductor heating depending on the pulse duration, velocity of surface recombination, lifetime of charge carriers, and their diffusion coefficient. Full article

Plant factories with artificial lighting (PFALs) are a notable choice for urban agriculture due to the system’s benefits, where light can be manipulated to enhance the product’s yield and quality. Our objective was to test the effect of light spectra with different red-blue combinations and white light on the growth, physiology, and overall quality of three baby-leaf vegetables (green lettuce, kale, and pak choi) grown in a restaurant’s PFAL. Leaf mass per area was lower under the most blue-containing treatments in all species. The performance indices (PI_abs and PI_tot) of the photosynthetic apparatus were lower under more red light with the exception of PI_abs in pak choi. Total soluble solids accumulation was diminished under most of the blue-containing LEDs, while total phenolics and antioxidant activity were induced by red-blue environments rich in blue light. Moreover, chlorophyll and carotenoid accumulation was also enhanced under blue-rich light treatments. Nitrate content was the lowest under monochromatic blue in all species. Finally, the employees were asked about their views on the PFAL within the restaurant’s compounds and they expressed positive opinions. Overall, a light environment including red and blue wavelengths proved beneficial for baby leafy vegetable production in terms of yield and quality. Full article

Sunflower is a crop species well adapted for cultivation in open fields under full sunlight. Young plantlets can be grown in growth chambers under low irradiance, where different aspects of light can be easily tracked. Using time-lapse imaging, we have shown how monochromatic red, blue, and far-red light and their combinations interacted, affecting the rhythmicity and elongation of sunflower hypocotyls. Monochromatic light of any color, applied individually, canceled all manifestations of diurnal rhythmicity and anticipation of imminent light transitions present in diurnal photoperiods established by white LED light panels. Monochromatic light also significantly increased the rate of hypocotyl elongation, which became uniform (arrhythmic) and often triggered the appearance of guttation. The rate of hypocotyl elongation was highest with the blue light and lowest with red light. In double light combinations, red light suppressed the stimulative effect of blue light, but it promoted the elongation rate when used together with far-red light. A triple light combination of red, blue, and far-red light stimulated hypocotyl elongation to a high degree and increased the elongation rate more than twofold compared with red and fourfold compared with white LED light. Full article

This study presents the design and fabrication of light retroreflectors utilizing surface plasmon resonance (SPR) in parallel-superimposed bi-grating structures. The bi-gratings were inscribed onto a thin azobenzene molecular glass film via photolithography and subsequently coated with a thin gold layer to support SPR. The two superimposed gratings operate in tandem, with one grating coupling incident light into the SPR mode and the other coupling it back out toward the light source, thereby achieving retroreflection. Monochromatic retroreflection is demonstrated for a target wavelength (785 nm) at angles from 5° to 10°, while multi-wavelength retroreflection is achieved for red, orange, and green wavelengths at corresponding angles. The findings highlight the potential of these bi-gratings for applications in optical sensing, communication, and advanced photonic systems, where compact, tunable, and angularly responsive designs are essential. Full article

Objectives: This laboratory study aims to assess the effects of misaligning different trifocal intraocular lenses (IOLs) under varying spectral and corneal spherical aberration (SA) conditions. Methods: With an IOL metrology device under monochromatic and polychromatic conditions, the following models were studied: AT ELANA 841P, AT LISA Tri 839MP, FineVision HP POD F, Acrysof IQ PanOptix, and Tecnis Synergy ZFR00V. The SA was simulated using an aberration-free and average-SA cornea. The modulation transfer function (MTF) was measured at different pupil sizes for the on- and off-axis lens positions. Results: The IOLs exhibited varying responses to decentration up to 1 mm, showing the lowest impact in polychromatic light. The least affected was AT ELANA, with an MTF loss of 15.7% to 28.4% at 50 lp/mm across the studied conditions. It was followed by PanOptix and FineVision, with the MTF loss ranging from 19.1% to 36.0% and from 21.2% to 46.6%. AT LISA showed a more substantial reduction, i.e., 41.2% to 64.8%, but it was still lower than that of Synergy (51.1% to 78.8%). When decentration was induced at a 4.5 mm distance, its effect was more evident in conditions that were closer to each IOL’s SA correction. A tilt of 5° had a lesser impact than 1 mm decentration, with the effect being more severe at 4.5 mm. Conclusions: The off-axis position affects the optical quality of trifocal IOLs. Low- rather than high-SA-correcting trifocals perform better under misalignment. In polychromatic light, the impact of misalignment is less evident, suggesting a potential mitigating effect of chromatic aberration. Full article

Light is a vital environmental cue that profoundly influences the development of plants. LED lighting offers significant advantages in controlled growth environments over fluorescent lighting. Under monochromatic blue LED light, wheat plants exhibited reduced stature, accelerated spike development, and a shortened flowering period with increased blue light intensity promoting an earlier heading date. In this study, we conducted a comprehensive transcriptome analysis to investigate the molecular mechanisms underlying wheat plants’ response to varying light conditions. We identified 34 types of transcription factors (TFs) and highlighted the dynamic changes of key families such as WRKY, AP2/ERF, MYB, bHLH, and NAC, which play crucial roles in light-induced gene regulation. Additionally, this study revealed differential effects of blue and red light on the expression levels of genes related to hormones such as cytokinin (CK) and salicylic acid (SA) synthesis as well as significant changes in pathways such as flavonoid biosynthesis, circadian rhythms, chlorophyll synthesis, and flowering. Particularly, blue light upregulated genes involved in chlorophyll synthesis, contrasting with the downregulation observed under red light. Furthermore, blue light enhanced the expression of anthocyanin synthesis-related genes, such as CHS, underscoring its role in promoting anthocyanin accumulation. These findings provide valuable insights into how light quality impacts crop growth and development. Full article

When a phosphor film based on a photonic crystal (PhC) is excited at the photonic band-edge wavelength, the absorption of excitation light increases, which can potentially enhance the color-conversion efficiency. In this study, we modeled a two-dimensional (2D) PhC quantum dot (QD) film with a square-lattice structure using the finite-difference time-domain method to theoretically investigate its optical properties. The embedment of a thin-film layer with a high refractive index on the surface of the QD film enables an effective localization of excitation light within the phosphor. A numerical estimation shows that the optimized 2D PhC QD film can enhance the light absorption by up to 4.2 times with a monochromatic source and by up to 1.8 times with a broadband (FWHM~30 nm) source compared to a flat-type reference QD film. Full article

A series of flexible polyacrylonitrile/TiO₂ (PAN/P25) multi-porous nanotubular membranes were successfully constructed by facile electrospinning combined with an ethylene glycol solvothermal induce strategy. The effects of P25 dosage and solvothermal time on the morphology of samples were systematically investigated, which were characterized in terms of surface morphology, microstructure, specific surface area, thermal analysis, wettability, photoelectrochemical and fluorescence spectra. Rhodamine B (RhB) and Escherichia coli (E. coli) were employed as simulated pollutants to evaluate photocatalytic degradation and antibacterial properties of the PAN/P25-3 multi-porous nanotubular membrane. The PAN/P25-3 membrane exhibited the highest photocatalytic degradation efficiency, with 96.1% degradation of RhB within 120 min under a xenon lamp light source and a photocatalytic inactivation rate of 95.8% for E. coli under 365 nm monochromatic light irradiation. The photocatalytic degradation mechanism of the PAN/P25-3 multi-porous nanotubular membrane for RhB was deduced from the results of 3D-EEM fluorescence and scavenger experiments of reactive species. Additionally, the cyclic photodegradation experiments demonstrated that the PAN/P25-3 membrane maintained excellent stability and photocatalytic performance after multiple degradation cycles, confirming its potential for sustainable wastewater treatment applications. Full article

In this paper, we report on the measurement of the optical properties (absorption and scattering coefficients) of photoluminescent turbid media using a homemade integrating sphere setup equipped with a tunable monochromatic light source. The hemispherical reflectance and transmission data are analyzed with the radiative transfer equation using a Monte Carlo simulation-based lookup table to obtain the optical properties of the sample. The results are compared with the optical properties received from a classical integrating sphere setup equipped with a broadband white light source. The additional light of the photoluminescence generates artifacts within the optical properties, which are not present using a monochromatic light source. Additionally, a batch of samples with a broad range of scattering coefficients and dye concentrations were prepared and characterized with the aforementioned setup. The findings can help to generate a digital twin with the optical properties of the sample, which improves the physically based rendering and the design of, e.g., white-light LEDs. Dental restoration and photodynamic therapy also benefit from determination of the optical properties of photoluminescent turbid media. Full article

The sweet basil Ocimum basilicum L. is the subject of numerous studies and is cultivated as a food and ornamental plant. Moreover, O. basilicum could be useful in the prevention of stroke ischemia, and its anticancer properties were recently shown. Caffeic acid derivatives, such as rosmarinic acid (RA), chicoric acid, salvianolic acids, and anthocyanins, provide the medicinal properties of basil. Therefore, investigations of the optimal growth conditions that can provide cost-effective cultivation of highly productive basil plants are relevant and important. The aim of the present work was to study the effects of a combination of soil composition and light conditions on the morphological and biochemical characteristics of O. basilicum. In totally artificial (indoor) environments, light-emitting diodes (LEDs) may provide a broad range of narrowband wavelengths with different intensities. This technology can lower operating costs. In addition to the spectral composition, light intensity (PPFD, µmol m⁻²s⁻¹) is an important parameter for the optimal growth of plants. In the experiment, we used different spectra of LED lamps with intensities of 300 µmol m⁻²s⁻¹: warm white, monochromatic (green and red), and a combination of blue and red. Plants were grown under various lighting conditions in soil supplemented with fertilizer, Z-ion, and Crystallon. The results showed that supplementation of soil with Crystallon had a greater effect on the growth of both above- and below-ground parts of O. basilicum plants. Interestingly, growing O. basilicum plants under R and RB light led to a 2-fold increase in the biosynthesis of both the key caffeic acid derivative RA and anthocyanin. However, given that under RB light, there is no positive effect of Crystallon on growth, the productivity of RA and anthocyanin reached a maximum when O. basilicum plants were grown under R light and Crystallon. Under these conditions, the productivity of anthocyanins and caffeic acid derivatives in O. basilicum was more than eight times greater than that in untreated O. basilicum plants. Full article

Using light-emitting diode (LED) in plant production optimizes growth with higher energy efficiency, reduces carbon footprint and resource consumption, and promotes more sustainable agriculture. However, the plants’ growth characteristics and biochemical composition may vary depending on the light’s wavelength, spectrum, and intensity. Therefore, LEDs as a light source have become a promising choice for improving cultivation efficiency, as they can modulate the spectrum to meet the needs of plants. Pereskia aculeata is a plant species from the cactus family with high protein, vitamins, minerals, and fiber. The objective of this study was to evaluate the effect of LED lighting on the cultivation of P. aculeata and its influence on biometric color and physicochemical aspects. Two treatments were carried out without the addition of artificial light: one inside the greenhouse (C-ins) and the other outside the greenhouse (C-out), and four treatments with LEDs in different spectral bands: monochromatic red (600–700 nm) (Red), monochromatic blue (400–490 nm) (Blue), white (400–700 nm) (White), and blue–red (1:1) (Blue–Red). The biometric characteristics and the color of the leaves collected from the different treatments were evaluated. After this, the leaves were dried, ground, and evaluated. The physicochemical and thermal characteristics, bioactive compounds, and antioxidant activity of the leaves from each treatment were described. The biometric characteristics were intensified with red LED, and the color of the leaves tended toward green. The dried yield was around 50%, except for C-out treatment. Regarding nutritional characteristics, the highest protein (29.68 g/100 g), fiber (34.44 g/100 g), ash (20.28 g/100 g), and lipid (3.44 g/100 g) contents were obtained in the treatment with red light. The red treatment also intensified the content of chlorophyll a (28.27 µg/L) and total carotenoids (5.88 µg/g). The blue treatment intensified the concentration of minerals and provided greater thermal stability. Regarding bioactive properties, the cultivation of P. aculeata inside the greenhouse favored the concentration of phenolic compounds and a greater antioxidant capacity. Therefore, the quality of light for P. aculeata demonstrates that the length of red and blue light corroborates the development of the plant through the wavelength absorbed by the leaves, favoring its characteristics and planting in closed environments. Full article

A variety of LED types can be employed for street and road lighting purposes. White phosphor-converted LEDs represent the most widely used option. However, amber LEDs are increasingly being used to reduce some negative effects associated with light pollution. These LEDs can be manufactured using both phosphor-converted and monochromatic direct chip technologies. This paper addresses the link between the reduction in short-wavelength light emissions which contribute to sky glow and the energy efficiency of LED-based road lighting. This paper focuses on an example illustrating the common misconception that reducing light pollution also means saving energy. Through the consideration of how spectral power distribution influences both mesopic vision and the amount of emitted blue light, it has been concluded that while monochromatic direct amber LEDs consume more energy than their white or amber phosphor-converted counterparts, their use in outdoor lighting is justifiable due to their potential effects of reducing sky brightness. Full article

Background: This paper aimed to measure and characterize eleven monochromatic filters and twenty-two combinations used empirically to treat patients with visual dysfunctions to propose enhanced protocols based on solid evidence. Their wavelength, transmittance, and relative sensitivity were defined on the retinal cone cells. Methods: A double-beam UV-VIS-NIR spectrophotometer, VARIAN brand, Cary 5000 model, owned by the National Center of Metrology, with high precision and accuracy, was used to characterize all filters. Filters were purchased from Optomatters Corporation, Belgium. Results: When two or three filters are combined, their transmittance and relative sensitivity on the retinal cone cells decrease regardless of wavelength. As a result, the efficiency of combined filters may decrease during treatments. Additionally, most filters and combinations, regardless of the wavelength, transmit a considerable percentage of light from the red spectrum. A depressant is the best monochromatic filter, and Upsilon–Neurasthenic is the strongest combination to stimulate blue cone cells. In contrast, Stimulant and Delta–Theta are best for red and green cone cells. Mu–Delta and Mu–Theta can be interchangeable, as well as Alpha–Delta and Alpha–Theta. Conclusions: Results suggest that the current phototherapy treatment protocol must be deeply revised, and the number of filters and combinations should be reduced to reduce costs and time and boost efficiency. Full article