Light Phenomena Research Articles

Study of ion separation mechanism in the multi-component vacuum arc discharge

The separation phenomenon of light and heavy ions was widely observed experimentally in the vacuum arc discharge with multi-component composite cathode. In this work, a two-dimensional axisymmetric multi-fluid model is used to study the separation mechanism in the multi-component composite cathode vacuum arc. The multi-component vacuum arcs are simulated as a whole which includes separate cathode spot jets, the mixing region, and common arc column. The results show that the plasma jets originated from the separate cathode spot mix together to form a common arc column after a certain distance from the cathode. Due to the rapid increase of ion temperature dozens of times in mixing region of cathode spot jet, the effect of pressure gradient becomes far greater than that of the collisions between light and heavy ions. This leads to a shift in the predominant ion motion mechanism from ion–ion collision (single cathode spot jet region) to pressure expansion (the mixing region). Finally, the light ions gain higher velocities under pressure expansion. In addition, the effect of thermal conductivity and viscosity leads to the wider high temperature regions for light ions, thus making a wider distribution of corresponding ion flux. The numerical results are qualitatively consistent with the experimental results. This paper provides an insight into ion separation mechanism in the multi-component vacuum arc.

Correlation between corneal tomography and postphacoemulsification positive dysphotopsia

ObjectivesThe aim was to compare between patients who have positive dysphotopsia after uncomplicated phacoemulsification surgery and those who do not have regarding their corneal tomographic findings.BackgroundDysphotopsia is a disturbance of vision and includes light phenomena such as haloes, the subjective perception of a bright ring around a light source. It occurs owing to optical nonconformities in the optical path such as cataract or optical boundaries.Patients and methodsThis is a prospective interventional study that was conducted for 1 year on 20 patients with acquired cataracts. Preoperative corneal tomography and visual assessment were carried out, and then postoperative periodic follow-up for 6 months was done with clinical and visual assessment for dysphotopsia.ResultsThis study shows that 40% of eyes (eight eyes) had higher order aberration with preoperative positive dysphotopsia and 60% of eyes (12 eyes) showed no higher order aberration with no preoperative positive dysphotopsia. Postoperative assessment of positive dysphotopsia showed that patients with no higher order aberrations complained of positive dysphotopsia and patients with higher order aberrations complained of positive dysphotopsia but more severe than before.ConclusionThis study concluded that there is a correlation between corneal tomography and postphacoemulsification positive dysphotopsia, which affects visual satisfaction of patients after phacoemulsification surgery.

Characteristics of spectral peaking in optical fibers

We investigated multiple spectral peak generation during a coherent supercontinuum generation process with normal-dispersion highly nonlinear fibers both numerically and experimentally. Wideband multiple spectral peak generation was achieved in the 1.6–1.7 μm range using an ultrashort-pulse fiber laser, a CH4 gas cell, and highly nonlinear fiber. The maximum signal-to-background ratio was ∼8.4. Thanks to the normal-dispersion fibers, the induced phase shifts in the absorption spectra were clearly observed on the spectra during the spectral peak generation. The intensity and phase noise properties of the generated spectral peaks were examined, and low noise properties were confirmed. The spectral peaking phenomenon was investigated experimentally in a fiber amplifier. Periodical spectral peaking was successfully observed for a soliton pulse with Kelly sidebands, and the optical pulse experienced absorption in HCN gas. It is expected that spectral peaking occurs for pulses that experience absorption in many different kinds of gas species or those with spectral peaks. This light source and phenomenon will be useful for developing novel optical frequency comb techniques and optical wavelength standards.

Exploring unconventional features of light dynamics in Aubrey–André–Harper model based quasi-periodic optical lattices

We report an Aubrey–André–Harper (AAH) model based quasi-periodic lossless evanescently coupled waveguide lattice to study the unconventional physics of light localization. We find an exclusively new way to establish localization phase transition in a 1D-AAH lattice by observing the slope variation of the band and accordingly study the modal characteristics to reveal the fact that a higher value of quasi-periodic modulation strength is imperative for observing a signature of fully localized light states having higher eigenenergy. This analytical concept has numerically been implemented in the proposed quasi-periodic lattice to achieve light localization, where we have shown that the supported states not only depend on localization phase transition parameter, but also on the specific location of excitation which is due to quasi-periodic nature of lattice. Furthermore, we have investigated a unique effect of the presence of disorder on light localization phenomenon, where it has been reported that the presence of off-diagonal disorder, which is otherwise detrimental, favours light localization in the proposed structure due to its quasi-periodic nature. The findings indeed have the potential to open up a fertile platform to manipulate light in passive photonic devices.

Dynamic Autonomous Identification and Intelligent Lighting of Moving Objects with Discomfort Glare Limitation

The importance of reducing discomfort glare during the dynamic development of high luminance LEDs is growing fast. Smart control systems also offer great opportunities to reduce electricity consumption for lighting purposes. Currently, dynamic “intelligent” lighting systems are a rapidly developing field. These systems, consisting of cameras and lighting units, such as moving heads or multimedia projectors, are powerful tools that provide a lot of opportunities. The aim of this research is to demonstrate the possibilities of using the projection light in dynamic lighting systems that enable the reduction of discomfort glare and the light pollution phenomenon. The proposed system allows darkening or reducing the luminance of some sensitive zones, such as the eyes or the head, in real-time. This paper explores the development of the markerless object tracking system. The precise identification of the position and geometry of objects and the human figure is used for dynamic lighting and mapping with any graphic content. Time measurements for downloading the depth maps, as well as for identifying the human body’s position and pose, have been performed. The analyses of the image transformation times have been carried out in relation to the resolution of the images displayed by the projector. The total computation time related to object detection and image display translates directly into the precision of fitting the projection image to a moving object and has been shown.

Energy Release in a Thundercloud Necessary for the Formation of Middle Atmosphere Transient Light Phenomena

Energy Release in a Thundercloud Necessary for the Formation of Middle Atmosphere Transient Light Phenomena

Eigenmode analysis of the waveguide-plasmon structure based on a-Si1-xCx:H layer with 1D gold grating

Resonant structure consisting of waveguide layer with metallic strips array is a promising design for various optical effects control and enhancement at the nanoscale due to its strong resonant properties and light localization phenomena. However, different applications require understanding the nature of eigenmodes of the structure, that possess peculiar properties. In this research, the optical properties of the planar waveguide with one-dimensional periodic gold grating on it was examined. Emitting layer of a-Si1-xCx:H was deposited by plasma chemical vapour deposition technique and the gold array was created by the e-beam lithography. Angle-resolved reflection and photoluminescence spectra in s- and p-polarizations were measured by the Fourier-imaging spectroscopy method. The theoretical analysis was performed to reveal the physical nature of the observed spectral features and their effect on the waveguide layer emitting properties was studied.

The Superluminal Phenomenon of Light Near the Kerr–Newman Black Hole or Super-Gravitational Source

We use the Kerr–Newman metric based on the theory of general relativity to discuss the observed superluminal phenomenon of light near the black hole and whether it is observable astronomically at infinity or a weak gravitational place such as on Earth. The black hole has the rotation term a and the charge term RQ as well as the Schwarzschild radius RS. The geodesic of light in the spacetime structure is ds2 = 0, and the equation for three velocity components (dr/dt, rdθ/dt, rsinθdϕ/dt) is obtained in the Boyer-Lindquist coordinates (r, θ, and ϕ) with the coordinate time t. Then, three cases of the velocity of light (dr/dt, 0, and 0), (0, rdθ/dt, and 0), and (0, 0, and rsinθdϕ/dt) are discussed in this research. According to our discussion, only the case of (dr/dt, 0, and 0) gives the possibility of the observations of the superluminal phenomenon and an example is shown at r between RS and (RQ2+a2sin2θ/2)/RS at sinθ>0, when RQ ∼ RS. The results reveal that the maximum speed of light and the range of the superluminal phenomenon are much related to the rotational term a and the charged term RQ. It is at least reasonable at two poles and in the equatorial plane, when light propagates along the radial direction. Although the superluminal phenomenon is discussed in the Boyer-Lindquist coordinates, all the results are easy to be transformed or discussed in the Cartesian coordinates (x, y, z, t) by setting R2 = x2+y2+z2 = r2+a2sin2θ and rdr = RdR in the velocity of light. The conclusions of the superluminal phenomenon about the three velocity components (dR/dt, Rdθ/dt, Rsinθdϕ/dt) are different from them in the Boyer-Lindquist coordinates. Generally speaking, the superluminal phenomena for light can possibly occur in these cases where the radial velocity dr/dt is dominant, and the other two velocity components are comparably small. When the relative velocity between the observer coordinate frame and the black hole is not large, the superluminal phenomenon is possibly observable at infinity or in a weak gravitational frame such as on Earth. The results can also be applied on the super-gravitational sources.

Bergenia ciliate-Mediated Mixed-Phase Synthesis and Characterization of Silver-Copper Oxide Nanocomposite for Environmental and Biological Applications.

Bergenia ciliate (B. ciliate) leaf extract was used as a reducing and stabilizing agent for the synthesis of silver-copper oxide nanocomposite (Ag-CuO NC). Scanning and transmission electron microscopies (SEM and TEM) were used to examine the structural morphology, and the average particle size was determined to be 47.65 nm. The phase confirmation and crystalline structure were examined through the X-ray diffraction (XRD) technique, where cubic and monoclinic geometries were assigned to Ag and CuO. The energy dispersive X-ray (EDX), Fourier transform infrared (FTIR) and ultra-violet and visible (UV-Visible) spectroscopies were operated to analyse the elemental composition, functional groups and light absorption phenomena of the Ag-CuO NC. Under the full light spectrum, the photodegradation of Rhodamine 6G was recorded, and 99.42 percent of the dye degraded in 80 min. The Agar well diffusion method was followed to perform antibacterial activity against selected pathogens, and the activity was found to increase with increasing concentration of Ag-CuO NC. The ABTS free radical scavenging activity suggests that the activity of Ag-CuO NC is higher than ascorbic acid.

A multi‐pass method for accelerated spectral sampling

AbstractSpectral Monte Carlo rendering can simulate advanced light phenomena, such as chromatic dispersion, but typically shows a slow convergence behavior. Properly sampling the spectral domain can be challenging in scenes with many complex spectral distributions. To this end, we propose a multi‐pass approach. We build and store coarse screen‐space estimates of incident spectral radiance and use these to then importance sample the spectral domain. Hereby, we lower variance and reduce noise with little overhead. Our method handles challenging scenarios with difficult spectral distributions, many different emitters, and participating media. Finally, it can be integrated into existing spectral rendering methods for an additional acceleration.

A dense stereo matching method based on optimized direction-information images for the real underwater measurement environment

The refraction phenomenon of light at the interface of different media causes the epipolar to bend (the traditional camera model is invalid), and the stereo matching can’t be performed under the row matching. Therefore, we proposed a new model based on light field, in which an underwater image is expressed with the direction-information image and position image. The underwater stereo matching is conducted in the direction-information image instead of the original underwater image because the curve constraint of the correspondence becomes the row constraint in the direction-information image. In addition, the essence of stereo matching is similarity detection, but the phenomenon of absorption and scattering in water causes problems such as blurred outlines and loss of a large number of details in real underwater images, which will cause great interference in the similarity detection process. Therefore, we propose an image optimization method that fuses color correction and Dark channel Prior to improve the quality of the directional-information image. Finally, the underwater stereo matching process is divided into three steps. In order to verify the feasibility and effectiveness of the proposed method, we carry out more experiments. The experimental results show that our method and equipment can be used for underwater 3D measurement with high accuracy.

Design and Reconstruction of Visual Art Based on Virtual Reality

Because traditional methods generally lack the image preprocessing link, the effect of visual image detail processing is not good. In order to enhance the image visual effect, a visual art design method based on virtual reality is proposed. Wavelet transform method is used to denoise the visual image and the noise signal in the image is removed; a binary model of fuzzy space vision fusion is established, the space of the visual image is planned, and the spatial distribution information of the visual image is obtained. According to the principle of light and shadow phenomenon in visual image rendering, the Extend Shadow map algorithm is used to render the visual image. Virtual reality technology was used to reconstruct the preprocessed visual image, and the ant colony algorithm was used to optimize the visual image to realize the visual image design. The results show that the peak signal-to-noise ratio of the visual image processed by the proposed method is high, and the image detail processing effect is better.

Ultra-compact, broadband adiabatic passage optical couplers in thin-film lithium niobate on insulator waveguides.

We report the first demonstration of broadband adiabatic directional couplers in thin-film lithium niobate on insulator (LNOI) waveguides. A three LN-waveguide configuration with each waveguide having a ridge cross section of less than 1 square micron, built atop a layer of SiO2 based on a 500-µm-thick Si substrate, has been designed and constructed to optically emulate a three-state stimulated Raman adiabatic passage system, with which a unique counterintuitive adiabatic light transfer phenomenon in a high coupling efficiency of >97% (corresponding to a >15 dB splitting ratio) spanning telecom S, C, and L bands for both TE and TM polarization modes has been observed for a 2-mm long coupler length. An even broader operating bandwidth of >800 nm of the device can be found from the simulation fitting of the experimental data. The footprint of the realized LNOI adiabatic coupler has been reduced by >99% compared to its bulk counterparts. Such an ultra-compact, broadband LNOI adiabatic coupler can be further used to implement or integrate with various photonic elements, a potential building block for realizing large-scale integrated photonic (quantum) circuits in LN.

Study on the PBGs of a two-dimensional photonic crystal with multilayer rings composite structure and its slow light in W1 waveguide

In this paper, we present a scatterer with a multilayer annular nested composite structure. The photonic band gaps (PBGs) characteristics of the two-dimensional photonic crystals and the slow light features of the W1 waveguide are studied by the plane-wave expansion method. The influences of the number and the thicknesses of hollow annular dielectrics on the PBGs are analyzed. Meanwhile, the impact of the refractive index of each dielectric column is also taken into account. Herein, the scatterers are placed in the square and triangular lattices, and the PBGs traits of the TE and the TM modes in different lattice arrangements are fully discussed. With five layers of dielectric, we get a wide range of complete PBGs. When the thickness and refractive index of the dielectric layer are constant, increasing the number of dielectric layers does not always contribute to boosting the PBG scope. With the aggrandizement in the number of dielectric layers, the PBGs of the TM mode are larger and larger, but the PBGs of the TE mode always aggrandize first and then reduce, or even die down. As the thickness of the dielectric layer is altered, the results depict that the PBGs appertain to the TE mode when the thickness is small, while the TM mode and absolute PBGs tend to occur with the condition that the thickness of the dielectric column is large. Besides, the width of the PBGs always aggrandizes to the accession in the refractive index, and when the refractive index adds to a certain value, the PBGs width degrades to the augment in the refractive index. Finally, the slow light phenomenon in the W1 waveguide with a diverse number of ring layers is analyzed by introducing line defects into the structure. In the GaAs waveguide, we obtain group velocities of ±0.23c.

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.

PHONOSEMANTISM AS PART OF THE SIGN SYSTEM OF LANGUAGE

Phonosemantics is a science with a thousand-year history, the attitude to which is ambiguous. Despite the fact that the main principle of this linguistic discipline about the motivation of the sound unit and the legitimacy of the phenomenon has been repeatedly questioned, although discussions on the universality and specificity of the phenomenon under study continue to this day. Language is the most powerful means of forming thought; social phenomenon that attest to such its main functions as informational, communicative, emotional, cognitive, epistemological, accumulative. All functions are usually implemented not in isolation, but in various combinations, because each statement in most cases is multifunctional. All functions ultimately work for communication, and that's in the sense that the communicative function is leading. Simultaneously with the acquisition of human language, it acquires knowledge about the world around, which significantly shortens and simplifies the path of cognition, protects a person from unnecessary mistakes. F. de Saussure explained the problem of the value of a linguistic sign, arguing that a linguistic sign combines a concept and an acoustic image and has two essential features: arbitrariness (unmotivated) and linearity (unfolding in time and one dimension). The sign is used to indicate an object outside it, to receive, store and transmit information. A sign acquires its meaning only in a certain system, because outside it is not a sign and means nothing. The palette of phonosemantic searches is inexhaustible, as each linguistic and literary-artistic direction in various manifestations considers the symbolism of images of phonemes, phonemes, morphemes, tokens, syntagms, texts. The scope of using linguistic units with existing phonosemantic features is different types of movement, sound, light phenomena, physiological and emotional states of both humans and animals.

A simple and low-cost surface treatment to facilitate charge extraction and eliminate light soaking of polymer solar cells

Recently, polymer solar cells (PSCs) based on low bandgap thienothiophene-benzodithiophene copolymer have exhibited rapidly raised efficiency, but light soaking phenomena has caused a great impact on device performance. Herein, Al3+ was introduced between indium tin oxides (ITO) electrode and poly[(9,9-bis(3′-(N,N-dimethylamino)propyl)-2,7-fluorene)-alt-2,7-(9,9-dioctylfluorene)] (PFN) electron extraction layer of PSCs. The incorporated Al3+ could not only effectively fill the defects on the surface of ITO, but also decrease electron transport barrier, which facilitates charge transfer and increases the dissociation of photogenerated excitons. As a consequence, the optimal buffer layer improves the photoconductivity response and suppresses the photocurrent hysteresis phenomena.

A new kinetics model to predict the growth of micro-algae subjected to fluctuating availability of light

Light is a key environmental factor for the growth of micro-algae, and optimizing the capture of light is critical for high efficiency production systems. As the density of the population of micro-algae increases, the availability of light decreases, leading to a reduction in the growth rate because of mutual shading, while other effects, such as photo-inhibition, might be especially frequent when the population density is low. Several models in the literature have been developed to take into account light phenomena and predict micro-algal growth, particularly in a mono-culture. With the help of a simple expression for the attenuation of the light, we propose and justify a new growth function that incorporates both photo-inhibition and photo-limitation. In agreement with the experimental data, this new formulation describes the micro-algal response to a wide range of situations of excessive or insufficient light intensities through an explicit dependence on both the incident light and the biomass concentration. While simple, the proposed expression can be satisfactorily applied to practical cases under nutrient replete conditions in photo-bioreactors with different sizes and geometries. It extends naturally to the growth of different species, providing a dynamic model which can simulate experiments in a mono-culture as well as in poly-cultures. The investigation of the competition for light-limited growth shows that the model predicts competitive exclusion, which has also been experimentally demonstrated. This leads to new perspectives for the control and optimization of mixed micro-algal cultures.

Fresnel diffraction is a basic quantum mechanical effect

Using the Fresnel–Kirchhoff integral, we express the state of the light that diffracts from an aperture to a point, by superposition of two or more waves. The amplitudes of the waves are determined by the distances of the point from the ray optics borders of the emerging beams. The interference approach to the Fresnel diffraction leads to a universal formulation of the normalized intensity distribution on the diffraction pattern that determines the state of the incident light, the parameters of the aperture, and its distance from the observation plane, uniquely. In the photon approach, according to the uncertainty principle, confining the position of a photon to an aperture changes the probable propagation direction of the photon in an interval that leads to the diffraction of the photon or light. Thus, the normalized intensity distribution on the diffraction pattern is the probability distribution of a photon. To this probability distribution, a probability amplitude distribution is associated that diffracts similar to a wave in Fresnel diffraction. Applying the introduced approach to the study of the diffraction, from different simple apertures and phase steps, we deduce general behaviors of the Fresnel diffraction and show it is involved in all aspects of light phenomena.

Design of flexibility mechanism for electricity market to promote the consumption of new energy

With the development of new energy, it is an irresistible trend for the demand side to consume new energy on a large scale and in a high proportion. At present, China’s installed capacity of new energy is growing rapidly, but the flexibility of the power system is insufficient, new energy consumption is difficult, and a large number of abandoned wind and light phenomena appear. In view of the high proportion of new energy consumption in the current environment, this paper designs the overall framework of the flexibility mechanism of the power market to promote new energy consumption, and puts forward the benefits of various market mechanisms in improving flexibility and promoting new energy consumption. Based on each market mechanism, the contribution index is put forward, the role of each market mechanism is analyzed quantitatively, and the considerable benefit of the market flexibility mechanism in promoting the consumption of new energy is proved by an example.