Light Phenomena Research Articles

Hook, Line, and Sinker! Spectroscopic Studies of Bi-Modular Mono- and Bis-1,8-naphthalimide-Ru(bpy)3-conjugates as DNA "Light Switches".

Bi-chromophoric ruthenium polypyridyl complexes comprising one or two nitro-1,8-naphthalimide groups are shown to be effective DNA binders with off–on light switching properties. The binding to DNA was investigated using a combination of studies such as UV–visible absorption and emission titrations, thermal denaturation, and circular dichroism spectroscopy. The DNA affinity was shown to be sensitive to both the linker length and the number of naphthalimides (one vs two) contained in these systems and binding constants ranging from 106 to 107 M–1 for salmon testes DNA. The strong DNA binding is attributed to the combination of naphthalimide intercalation and the electrostatic interaction of the ruthenium complex. Large emission enhancements from the metal to ligand charge transfer (MLCT) emission arising from the metal complex were observed upon DNA binding, which was attributed to the interruption of intramolecular electron transfer quenching processes. Moving the nitro substitution from the 4-position to the 3-position is found to result in modification of the DNA binding and the resulting optical properties. The off–on light switch phenomena reported demonstrate the potential of these complexes to act as DNA probes.

Stray Light Nonuniform Background Elimination Method Based on Image Block Self-Adaptive Gray-Scale Morphology for Wide-Field Surveillance

Space-based wide-field surveillance systems are of great significance in maintaining the security of space resources by avoiding collisions between space targets. However, their performance is hindered by stray light phenomena. The nonuniform background noise caused by stray light significantly hampers subsequent target detection, leading to a high frequency of false alarms. To solve this problem, we propose a robust and accurate nonuniform background elimination method based on image block self-adaptive gray-scale morphology (IBSGM). First, we define two kinds of structural operators with different sizes and domains, which make full use of the difference between the target pixels and surrounding background pixels. Then, we block the original surveillance image and find the size of the largest target in each block by the minimum bounding rectangle method to determine the optimal size of the structural operator suitable for each block. Finally, we perform morphological processing using the defined structural operators to eliminate nonuniform backgrounds from images. Experimental results on simulated and real image datasets demonstrate that the proposed IBSGM method has higher precision in eliminating the nonuniform background when compared to other methods.

All angle polarization-independent photonic spin Hall effect

The photonic spin Hall effect (PSHE) is inherently a polarization-dependent phenomenon of incident light. In this work, the Spin-Orbit coupling of light-led PSHE has been manipulated to vanish its polarization dependency for all incident angles. This work demonstrates that the horizontal (H) and vertical (V) polarized PSHE will remain the same; (δ±H=δ±V) for any plane-polarized incident wave at any incident angle. Equal absolute Fresnel reflection coefficients (rs=rp) and their equal angular derivatives ∂rp/∂θi and ∂rs/∂θi are the underlying conditions for polarization-independent PSHE (PI-PSHE), which is achieved from the reflected light through a glass-metal (Ag, Au, or Al) thin film interface. Furthermore, the provided assembly of the planar metal-dielectric interface allows for controlling the device's characteristic size in an extensive range from 0.1λ to any bulk size, just by adjusting the thickness of the covered thin glass layer. We believe that our findings will pave the way for the development of new polarization-independent nano-photonic devices.

Transparency and Enhancement in Fast and Slow Light in q‐Deformed Optomechanical System

AbstractNonclassical phenomena can be enhanced by introducing q‐deformation in optomechanical systems. This motivates investigation of the optical response in a q‐deformed linearly coupled optomechanical system. The system consists of two deformed cavities that are linearly coupled to the motion of mechanical mirrors, and the cavities are coupled to each other by transmission strength parameter. This study shows that compared to non‐deformed cases, the deformed system exhibits more rapid phase transition at the positions of transparency windows, causing stronger and enhanced fast and slow light phenomena. Moreover, in the region , the optomechanical system results in gain. Additionally, for a fixed deformation of cavities, by tuning the tunneling strength and optomechanical coupling, one can observe a delay and advancement in probe field in the order of milliseconds and even above milliseconds for fine‐tuning of the coupling parameters. Finally, the bridge between mathematical and physical models is built by assuming the deformation to be a primitive root of unity, which indicates a class of anyon models. These results demonstrate that q‐deformation provides a novel method for manipulating and significantly enhancing optical phenomena not only in arbitrarily deformed optomechanical systems but also in anyon models.

Surface Electromagnetic Waves near a Black Hole Event Horizon and Their Observational Consequences

Localization phenomena in light, scattering from random fluctuations of matter fields and space–time metrics near a black hole horizon, were predicted to produce a pronounced peak in the angular distribution of second-harmonic light in the direction normal to the horizon. Therefore, the detection of second-harmonic generation may become a viable observational tool to study spacetime physics near event horizons of astronomical black holes. The light localization phenomena near the horizon may be facilitated by the existence of surface electromagnetic wave solutions. In this communication, we study such surface electromagnetic wave solutions near the horizon of a Schwarzschild metric, describing a black hole in vacuum. We demonstrate that such surface wave solutions must appear when quantum gravity effects are taken into account. Potential observational evidence of this effect is also discussed.

Prediction of phosphenes occurrence in patients undergoing photon irradiation to ocular structures due to brain tumor.

Phosphenes are visual light phenomena that are experienced when there is no apparent light that stimulates the eye. In oncology, phosphenes are also present during radiation therapy for patients with tumors of the central nervous system, eyes, head and neck. Due to the discomfort of patients treated with irradiation to the head regions, research is conducted to determine whether the dose to the ocular structures is predictive for the occurrence of phosphenes. The objective was to demonstrate the relationship between the doses of the retina and vitreous humour with the appearance of phosphenes. A descriptive study was carried out in a prospective cohort in 25 patients older than 18 years, with malignant tumours located at the level of the brain, both of primary and secondary origin, subjected to irradiation in 6 MV linear accelerators, during February 2020 to January 2021. As independent variables: Retinal dose and vitreous humour dose, and as dependent variables: Light flashes and stable light. Logistic regression analysis was used for prediction, using the SPSS statistical program (version 26.0). A final date of 380 external radiotherapy treatments. The presence of any of the events in a prevalence of 58.7% of the total of fractions. The distribution for the presence of both events, flash of light and stable light, was 69.1%, 20.6% and 10.3% respectively. In the logistic regression analysis, for the light flare, only the dose factor in vitreous was significant (OR: 1.74, IC [1.059-2.419] p: 0.001). For stable light, the dose in the retina (OR: 1.73, IC [1.121-2.341] p: 0.005), and dose in the vitreous humor (OR: 1.82, IC [1.335-2.315] p: 0.003). There is a predictive relationship between the doses of irradiation of the retina and vitreous humour, for the generation of phosphenes. These results help radiotherapy centres take these anatomical structures into account to reduce the presence of phosphenes in patients. Likewise, it would help to reduce phosphenes, keeping the bunker area illuminated during the treatment.

Emergent entanglement structures and self-similarity in quantum spin chains.

We introduce an experimentally accessible network representation for many-body quantum states based on entanglement between all pairs of its constituents. We illustrate the power of this representation by applying it to a paradigmatic spin chain model, the XX model, and showing that it brings to light new phenomena. The analysis of these entanglement networks reveals that the gradual establishment of quasi-long range order is accompanied by a symmetry regarding single-spin concurrence distributions, as well as by instabilities in the network topology. Moreover, we identify the existence of emergent entanglement structures, spatially localized communities enforced by the global symmetry of the system that can be revealed by model-agnostic community detection algorithms. The network representation further unveils the existence of structural classes and a cyclic self-similarity in the state, which we conjecture to be intimately linked to the community structure. Our results demonstrate that the use of tools and concepts from complex network theory enables the discovery, understanding and description of new physical phenomena even in models studied for decades. This article is part of the theme issue 'Emergent phenomena in complex physical and socio-technical systems: from cells to societies'.

Dataset for measuring the conceptual understanding of optics in Rwanda.

This dataset is an accumulation of data collected to test Rwandan physics students' conceptual understanding of light phenomena and to assess instructional tools for active learning of optics. We collected and analysed data from 251 grade 11 (senior 5) students using our Light Phenomena Conceptual Assessment (LPCA) tool and from 136 grade 10 (senior 4) students using Geometric Optics Conceptual Understanding Test (GOCUT) in 2019. Before collecting data, we designed and validated LPCA and GOCUT, and tested their reliability. Data were collected before and after students learnt about the unit of light. Both day and boarding schools in rural and urban areas were included in our sampling. Data collected were test scores from students after performing a 30-item LPCA test or 25-item GOCUT test in 40 minutes. The data may be reused to extend students' understanding of optics concepts through item analysis, analysis of school characteristics such as location and school type, or by analysing students' characteristics such as subject combinations.

All-optical memory based on slow light and Kerr effect in photonic crystal platform with independent write/read/hold control

A general scheme has been proposed for the design of photonic-crystal-based all-optical memory by implementing the Kerr effect and slow light phenomenon and a memory cell with independent control on the read, write and hold processes is presented. A photonic crystal slab platform comprised of air holes in a square array with a hole radius of R = 192.5 nm and slab thickness of 275 nm is considered to realize the optical memory operating at the signal and pump wavelengths of λ = 1550 nm and λ = 1604 nm, respectively. The radii of the holes and the thickness of the proposed slab are engineered to provide proper functionality in the write/read waveguides and memory cell. For the slab thickness of 275 nm, the radii of the defect holes at the center of the read and write channels, and memory cell are determined to be 66 nm, 60.5 nm, and 55 nm, respectively. The pump pulse with a peak power of 2.65 W and a minimum time duration of ∼2.64 ps is required for the reading process. Also, the peak power and minimum time duration of 4.7 W and 1.35 ps, respectively are required to accomplish the writing process. The study has been carried out by 3D PWE and 3D FDTD methods.

Single-photon blockade in quasichiral atom–photon interaction: simultaneous high purity and high efficiency

We investigate the single-photon blockade (1PB) in the quasichiral regime of atom–photon interaction, where the effective coupling between the cavity and the atom is bidirectional but asymmetrical, achieved by coupling to a dissipative environment. A synthetic magnetic current ϕ is induced in the closed-loop coupling, which breaks down the reciprocity of atom–photon interaction, and can be utilized to create asymmetrical or even unidirectional effective coupling between two selected quantum states. As an example, we couple the single-atom cavity quantum electrodynamics (QED) system to a strongly dissipative plasmonic cavity. We find that in the quasichiral regime, the unconventional photon blockade (UPB) and the conventional photon blockade (CPB) realize simultaneously in the condition of maximum chirality (ϕ = π/2 and 3π/2). As a result, 1PB in the quasichiral regime can combine the advantages of both UPB and CPB, demonstrating the perfect single-photon purity, higher efficiency, non-oscillating time dynamics as well as lower requirement of mode coupling to achieve UPB. Our work paves the way for 1PB towards practical applications and reveals the intriguing quantum-optics phenomena in the quasichiral light–matter interaction.

Analysis of the gradual transition from the near to the far field in single-slit diffraction

In Optics it is common to split up the formal analysis of diffraction according to two convenient approximations, in the near and far fields (also known as the Fresnel and Fraunhofer regimes, respectively). Within this scenario, geometrical optics, the optics describing the light phenomena observable in our everyday life, is introduced as the short-wavelength limit of near-field phenomena, assuming that the typical size of the aperture (or obstacle) that light is incident on is much larger than the light wavelength. With the purpose to provide an alternative view on how geometrical optics fits within the context of the diffraction theory, particularly how it emerges, the transition from the near to the far field is revisited here both analytically and numerically. Accordingly, first this transition is investigated in the case of Gaussian beam diffraction, since its full analyticity paves the way for a better understanding of the paradigmatic (and typical) case of diffraction by sharp-edged single slits. This latter case is then tackled both analytically, by means of some insightful approximations and guesses, and numerically. As it is shown, this analysis makes explicit the influence of the various parameters involved in diffraction processes, such as the typical size of the input (diffracted) wave or its wavelength, or the distance between the input and output planes. Moreover, analytical expressions have been determined for the critical turnover value of the slit width that separates typical Fraunhofer diffraction regimes from the behaviors eventually leading to the geometrical optics limit, finding a good agreement with both numerically simulated results and experimental data extracted from the literature.

Raman fl uorescence technologies for early detection of infl ammatory and oncological disorders as a part of public health strategy and a tool for improving the quality of medical care: a review

The increasing morbidity and mortality rate in inflammatory and oncological diseases requires determining the public health strategies for early detection of such disorders and improving the quality of medical care. For this goal, high-tech modalities with high sensitivity, specificity and accuracy are to be worked out. Rаman fluorescent medical technologies (RFMT) can be successfully applied in the diagnostics of inflammatory and tumor diseases if to develop a specific algorithm for express analysis of histological, physiological, microbiological and other components of biological tissues. The given article presents a brief overview on the application of Raman fluorescence spectrometry in the diagnostics of diseases. This medical technology, which utilizes the phenomenon of tissue autoflorescence and Raman light scattering, is a promising tool for early diagnostics of different inflammatory and oncological pathologies. The described nоn-invasive method allows to make an express assessment of metabolic, morphometric and functional tissue parameters in intact and in pathological tissue. The present discussion is aimed to find out points for the application of Rаman fluorescence spectrometry and its various modifications; to assess its potentials for screening; to develop a specific algorithm for the diagnostics of inflammatory and tumor pathologies. RFMT is a promising modality for future applications so as to improve the quality of medical care by early detection of inflammatory and tumor diseases and early prescription of rational therapy.

Prospects of Raman-fluorescent medical technologies as early detection of inflammatory and tumor head and neck diseases for improving quality of medical care: short review and original data

The quality of medical care depends on many parameters, including the effective use of high-tech medical interventions for the purpose of early identification of diseases. Today, it is important to use non-invasive, highly specific, accurate, highly sensitive, real-time express-methods of diagnostics. For such aim Raman fluorescent medical technologies can be used in detection of inflammatory and tumor diseases, including the head and neck pathology. This article provides a brief overview of the prospects of Raman fluorescence spectrometry in combination with machine learning methods for the early indication of head and neck diseases; also results of the study are presented. The technique is based on the phenomena of tissue autofluorescence and Raman light scattering. The article presents the results of the use of Raman fluorescence spectrometry for the differential diagnosis of ear diseases and salivary glands` pathology. In the future, the described method in case of special diagnostic algorithms` development can be used in clinical medicine for improving the quality of medical care.

Titania Enhanced Photocatalysis and Dye Giant Absorption in Nanoporous 1D Bragg Microcavities.

Light trapping effects are known to boost the photocatalytic degradation of organic molecules in 3D photonic structures of anatase titania (a-TiO2) with an inverse opal configuration. In the present work, we show that photocatalytic activity can also be enhanced in a-TiO2 thin films if they are incorporated within a nanoporous 1D optical resonant microcavity. We have designed and manufactured multilayer systems that, presenting a high open porosity to enable a straightforward diffusion of photodegradable molecules, provide light confinement effects at wavelengths around the absorption edge of photoactive a-TiO2. In brief, we have observed that a nanoporous 1D Bragg microcavity prepared by electron beam evaporation at oblique angles comprising a central defect layer of nanoporous a-TiO2 boosts the photocatalytic degradation of nitrobenzene and methyl orange dye solutions. The multilayer structure of the microcavity was designed to ensure the appearance of optical resonances at the a-TiO2 layer location and wavelengths around the absorption onset of this semiconductor. In this porous 1D Bragg microcavity, the diffusion constraints of molecules through the capping layers covering the a-TiO2 are effectively compensated by an increase in the photocatalytic activity due to the light confinement phenomena. We also report that the absorption coefficient of methyl orange dye solution infiltrated within the pore structure of the microcavity is exalted at the wavelengths of the corresponding optical resonances. This effect gives rise to a small but non-negligible visible light photodegradation of dye molecules. The possibilities of tailoring the design of 1D photonic systems to boost the photocatalytic activity of a-TiO2 are discussed.

Quantitative Assessment of Architectural Lighting Designs

There has recently been a great interest in the outdoor lighting that is energy-efficient and does not intensify a light pollution phenomenon. In architectural lighting, these demands are difficult to implement and rarely analyzed. However, it is possible to introduce and use certain parameters based on the utilization factor for the quantitative assessment of floodlighting design in terms of both light pollution and energy efficiency. This paper presents the definitions of new parameters and the results of their calculations for several typical architectural objects. Different lighting concepts were created for each object together with appropriate computer simulations. The research shows a high potential for usefulness of new parameters in the design process. The floodlighting utilization factor is characterized by relatively low values of around 35%. In addition, obtaining the recommended lighting power density value below 2.2 W/m2 does not sufficiently determine the correctness of the design implementation considering the natural environment. This determines a great potential for opportunities to improve the implemented designs and provides a basis for redefining the currently used approach in architectural lighting. In order to create high-quality, sustainable solutions, all quantitative parameters should be analyzed simultaneously in addition to the esthetic visual effect issue.

Short communication: Experimental factors affecting fission-track counts in apatite

Abstract. The tools for interpreting fission-track data are evolving apace, but, even so, the outcomes cannot be better than the data. Recent studies showed that track etching and observation affect confined-track length measurements. We investigated the effects of grain orientation, polishing, etching and observation on fission-track counts in apatite. Our findings throw light on the phenomena that affect the track counts and hence the sample ages, whilst raising the question: what counts as an etched surface track? This is pertinent to manual and automatic track counts and to designing training strategies for neural networks. Counting prism faces and using the ζ calibration for age calculation are assumed to deal with most etching- and counting-related factors. However, prism faces are not unproblematic for counting, and other surface orientations are not unusable. Our results suggest that a reinvestigation of the etching properties of different apatite faces could increase the range useful for dating and lift a significant restriction for provenance studies.

Developmental Trends in the Application and Measurement of the Bidirectional Reflection Distribution Function.

The bidirectional reflection distribution function (BRDF) is among the most effective means to study the phenomenon of light–object interaction. It can precisely describe the characteristics of spatial reflection of the target surface, and has been applied to aerial remote sensing, imaging technology, materials analysis, and computer rendering technology. This study provides a comprehensive review of the development of devices to measure the BRDF. We gathered research in the area by using the Web of Science Core Collection, and show that work on the BDRF has been ongoing in the last 30 years. We also describe some typical measurement devices for the BRDF proposed in the literature. Finally, we summarise outstanding problems related to BRDF measurement and propose directions of future research in the area.

Predicción de ocurrencia de fosfenos en pacientes sometidos a irradiación con fotones a estructuras oculares por tumor cerebral

Background and objectivePhosphenes are visual light phenomena that are experienced when there is no apparent light that stimulates the eye. In oncology, phosphenes are also present during radiation therapy for patients with tumors of the central nervous system, eyes, head and neck. Due to the discomfort of patients treated with irradiation to the head regions, research is conducted to determine whether the dose to the ocular structures is predictive for the occurrence of phosphenes. The objective was to demonstrate the relationship between the doses of the retina and vitreous humor with the appearance of phosphenes. Material and methodA descriptive study was carried out in a prospective cohort in 25 patients older than 18 years, with malignant tumors located at the level of the brain, both of primary and secondary origin, subjected to irradiation in 6MV linear accelerators, during February 2020 to January 2021. As independent variables: Retinal dose and vitreous humor dose, and as dependent variables: Light flashes and stable light. Logistic regression analysis was used for prediction, using the SPSS statistical program (version 26.0). ResultA final date of 380 external radiotherapy treatments. The presence of any of the events in a prevalence of 58.7% of the total of fractions. The distribution for the presence of both events, flash of light and stable light, was 69.1%, 20.6% and 10.3% respectively. In the logistic regression analysis, for the light flare, only the dose factor in vitreous was significant (OR: 1.74; 95% CI: 1.059-2.419; p: 0.001). For stable light, the dose in the retina (OR: 1.73; 95% CI: 1.121-2.341; p: 0.005), and dose in the vitreous humor (OR: 1.82; 95% CI: 1.335-2.315; p: 0.003). ConclusionsThere is a predictive relationship between the doses of irradiation of the retina and vitreous humor, for the generation of phosphenes. These results help radiotherapy centers take these anatomical structures into account to reduce the presence of phosphenes in patients. Likewise, it would help to reduce phosphenes, keeping the bunker area illuminated during the treatment.

Non-invasive imaging through scattering medium beyond the memory effect via polarization-modulation

The phenomenon of light scattering has brought challenges to many fields. In recent years, a novel method based on speckle-correlation has been proposed to look through scattering medium. However, the field of view (FOV) of this method is limited by the angular range of the optical memory effect (OME). In this paper, a polarization modulation-based method is proposed to look through the scattering medium beyond the OME range. This method can achieve single-shot non-invasive looking through multilayer scattering medium by using a polarization camera. Targets beyond the 4 times OME range is recovered by a single shot and a larger one also can be restored by moving the camera to collect the light signal. Unlike other methods that aim at imaging beyond OME, this method can reconstruct targets without reference points. The proposed method has no restriction on the target distribution, and both a single target or two separate targets can be recovered. The effectiveness of the method is verified through experiments.

Automatic Control System Using Arduino UNO and Web-Based Monitoring For Watering Chili Plants

Caring for chili plants in addition to fertilization is proper watering. Watering is sometimes done less regularly in this case is the timeliness other than that the temperature and soil moisture are not paid attention to by the chili plant keepers. Moreover, if the chili plant keeper has other activities, then the watering of the plants will be more irregular, making the production of chili plants not optimal and even chili plants can die. By utilizing Arduino and several supporting sensors, we can determine the right watering time. In this research, data is taken from sensors, such as soil moisture sensors, air humidity sensors, temperature sensors and ultrasonic sensors which then the data will be sent to the website to be displayed to the user. Sensors are devices used to detect changes in physical quantities such as pressure, force, electrical quantities, light, motion, humidity, temperature, speed and other environmental phenomena. The purpose of this study was to measure soil moisture, air humidity, temperature as a determinant of the right watering time for chili plants and make it easier for farmers to monitor and water chili plants. This is evidenced in the Blackbox testing method on the system design, from the test results it is known that this system has been running well and is in accordance with what is expected.