Hasil untuk "Optics. Light"

Muhammad Salman Mohsin, Katrina Fitzpatrick, Mariana Lanzarini-Lopes

This study provides a novel mathematical model for predicting the coupling efficiency (C.E) between multimode optical fibers (MMF) and ultraviolet light-emitting diodes (UV-C LEDs) with a high degree of accuracy. Unlike previous models, which rely on simplified assumptions (ideal conditions), this approach incorporates real-world variations in LED emission profiles, optical misalignments, and Fresnel losses. The model was validated using four distinct optical system configurations, demonstrating strong agreement (R2 = 0.94) with experimental data. The results from this study provide a robust framework for designing efficient UV delivery systems, particularly for disinfection and sensing applications and will serve as a practical guideline that may be useful for both the scientific and industrial community.

Srimathi Krishnaswamy, Yashpal, Puspamitra Panigrahi et al.

Different concentration of Dysprosium (Dy)(0, 0.25, 0.5, 1, 2, 3 and 4 %) was doped in zinc oxide by solid-state sintering method and investigated the effect of different concentrations of Dysprosium on crystallite size, morphology and optical studies on ZnO. Spherical morphology with 90 nm was revealed by Scanning electron microscopy with a low bandgap (3.033 eV) and was noticed for the higher concentration of Dysprosium in ZnO lattice. Room temperature photoluminescence was investigated in detail. The different weight percentage of 4 % Dy doped ZnO was added in polyvinyl alcohol and a thin film was fabricated and the optical properties were investigated in detail. 2Dy-ZnOF exhibited higher transmittance (42 %) and a lower bandgap(3.18 eV) was noticed. The peaks at 482 nm and 492 nm correspond to the transition of 4F 9/2 to 6H 15/2 and 4F 9/2 to 6H 13/2 respectively. This transition is due to the magnetic dipole transition and electric dipole transition. Further, a weak emission at 651 nm is due to 4F 9/2 to 6H 11/2 transition. CIE color chromaticity revealed for flexible Dy doped ZnO/PVA thin film in the white light region. Hence it could be a potential candidate for White Light LEDs.

R. Webb, G. Hughes, F. Delori

A confocal scanning imager moves an illumination spot over the object and a (virtual) detector synchronously over the image. In the confocal scanning laser ophthalmoscope this is accomplished by reusing the source optics for detection. The common optical elements are all mirrors-either flat or spherical-and the scanners are positioned to compensate astigmatism due to mirror tilt. The source beam aperture at the horizontal scanner is small. Light returning from the eye is processed by the same elements, but now the polygon's facet is overfilled. A solid-state detector may be at either a pupillary or retinal conjugate plane in the descanned beam and still have proper throughput matching. Our 1-mm avalanche photodiode at a pupillary plane is preceded by interchangeable stops at an image (retinal) plane. Not only can we reject scattered light to a degree unusual for viewing the retina, but we choose selectively among direct and scattered components of the light returning from the eye. One (of many) consequences is that this ophthalmoscope gives crisp and complete retinal images in He-Ne light without dilation of the pupil.

W. Bachalo, M. Houser

Lei Zhang, Bo Li, Hanshuang Li et al.

Signal-to-noise ratio (SNR) analysis is a crucial component of optical system development for space remote sensing instruments. It serves as a quantitative assessment of the imaging quality and radiometric characteristics of space remote sensing. This paper utilizes the working principles and energy transfer principles of space remote sensing instruments to conduct SNR analysis and model development for commonly used spaceborne imagers, spaceborne imaging spectrometers, micro-optical remote sensing instruments, and point-source spatial targets. Additionally, the paper also examines the impact of the presence and width of slits in different space environments on the SNR of space remote sensing instruments. The calculation results indicate that the analysis of Signal-to-Noise Ratio (SNR) for different space remote sensing instruments requires the establishment of distinct SNR models. The magnitude of SNR primarily depends on crucial factors such as optical system quality, detector performance, and the space environment. Therefore, in the instrument design and data processing processes, it is essential to consider how to maximize SNR and establish more accurate corresponding SNR models to provide high-quality remote sensing data.

Hongyu Guan, Manolo Dulva Hina

Given the recent advances in information technology, speed has become an important requirement in data transmission. In this regard and given that an LED (light emitting diode) can turn on and off for several thousands, even millions, of times per second, then LiFi (light fidelity) technology has strong advantages over WiFi (wireless fidelity) in terms of speed in data transmission. In this research project, a consortium of industrial and academic partners have decided to evaluate the maturity of LiFi technology by designing a demonstrator that showcases an efficient and speedy intra-vehicle data transmission system. The demonstrator implements a two-way LiFi communication between the reading light of a vehicle and a portable device, such as a tablet or smartphone. This nomadic device must display, via an interface, receiving transmitted data in real time. The data is of type RNT (Digital Terrestrial Radio) and TNT (Digital Terrestrial Television) provided by an in-house antenna. LiFi depends on optical technology hence, the devices’ optical characteristics have significant influences on the system. This paper presents various conducted experiments and techniques to improve the system’s throughput, communication range, and reception area. For instance, by replacing the reading light with one of better optical characteristics, the communication range and reception area improve. By using symmetrical power supply, the throughput improves. In the same manner, by using optical filters that eliminate noise, throughput likewise improves. We have indeed demonstrated that LiFi data transmission in the vehicle is feasible; low-definition videos were successfully transmitted. The paper also presents various possible techniques to still improve the system performance.

Ivan Romanov, Irina Parkhomenko, Liudmila Vlasukova et al.

It has been shown that Sn implantation with subsequent annealing in air leads to an increase in the electroluminescence (EL) intensity of SiO2/Si structure by two orders of magnitude. Intense violet EL with a maximum at 3.21  eV was observed at room temperature by the naked eye at forward bias. The observed emission was attributed to radiative recombination in SnO2 nanocrystals synthesized in SiO2 layers. The external quantum efficiency (EQE) increased with decreasing Sn concentration The maximum external quantum efficiency was found to be 0.7 % for the silica film Sn-implanted at the lowest fluence of 2.5 × 1016 cm−2. The non-radiative charge transport (shunt current) through the sample and mechanism of EL excitation are discussed. It has been concluded that the Poole–Frenkel mechanism, or tunneling between traps are the most likely mechanisms of charge transport to light-emitting centers.

An‐Chi Wei, Sheng‐Hsiang Wang, Jyh‐Rou Sze et al.

The hole accelerator is proven to benefit the hole injection for traditional light‐emitting diodes (LEDs) because the induced electric field provides the holes with more kinetic energy to pass through the electron‐blocking layer, enhancing the hole injection efficiency. Herein, the effect of the hole accelerator (HA) layer on the micro‐LEDs by modeling the characteristics of the devices with a current density of lower than 10 A cm−2 is investigated. The simulation results show that the appended HA layer brings a knot of the electric field in the HA layer, leading to higher internal quantum efficiency (IQE) than the device without HA under the low current density. The thickness and composition of HA, the quantum number, and the material of quantum barrier are also simulated and analyzed. The simulated radiative, Shockley–Read–Hall, and Auger recombination rates show that the IQE of the micro‐LED with the HA layer is higher than that without the HA layer under the current density of lower than 10 A cm−2.

F. Dnaya, D. Soubane, M. Bouhassoune et al.

Silicon, traditionally known as an indirect band gap semiconductor, unveils intriguing properties at the nanoscale, stemming from deviations from k-conservation rules within nanostructures. In our study, we scrutinized four hydrogenated Si 0D-nanostructures—Si10H16, Si14H20, Si18H24, and Si22H28—to unravel their dynamic stability under thermal fluctuations and optical characteristics. We initiated our exploration by employing the TD-DFT framework to generate and analyze the optical properties of these geometrically optimized nanostructures. Simultaneously, we conducted ab initio molecular dynamics simulations to examine the structural robustness and thermal stability of the four structures. Leveraging the Car-Parrinello molecular dynamics approach within the Quantum ESPRESSO open software suite, we observed temperature evolution and stability differences among the nanostructures at targeted temperatures 40 and 300 K. Our subsequent investigation delved into the Turbo-Lanczos time-dependent DFT method, unraveling the optical properties and excited-state dynamics of hydrogenated Si nanostructures. The results unveiled shifts towards higher energy absorption edges E0, accompanied by alterations in the permittivity tensor, complex refractive index, oscillator strength, and reflectivity. Notably, the analysis revealed an enlarged HOMO-LUMO gap, distinctive from bulk Si. Furthermore, our models predicted the elimination of phase-dependent E1/E2 optical transition peaks in the imaginary part of the dielectric function, and a gradual decrease in the low-frequency dielectric response with increased hydrogenation of the amorphous structures. These findings underscore the promising applications of hydrogenating Si nanostructures in diverse technological domains such as optoelectronics, memristors, sensors, and quantum computing. Their tunable optical properties, size-dependent behaviors, and compatibility with existing silicon-based devices make them particularly appealing for next-generation technologies.

Jinyong Zhang, Xuegang Xin

<italic>Objective:</italic> Calcium imaging is an essential tool for obtaining neuroactivities to understand the complex function of the brain. The one-photon miniscope, the most widely used endoscope in neuroscience, is employed to record neuronal calcium activities in vivo. However, the current half ball lens overlooks the energy distribution in the brain field, resulting in non-uniform fluorescence imaging and the omission of important signals, leading to misunderstanding in brain science. The main flaw in the existing lens is the lack of controlled energy distribution, where the center fluorescence is much stronger than the edge area, causing the fluorescence noisy background to overlap with numerous neuron signals. To address this issue, we propose a novel approach to simplify the optical path by setting a medial target. By combining the Ray Mapping Method and Energy Feedback Method, we design and optimize the lens based on the energy mapping mesh. Simulation results demonstrate a 2.1-fold enhancement in energy distribution uniformity in the brain field compared to the original half-ball lens, with edge neurons receiving 6.95 times more energy. This novel design is theoretically proved to be an innovative improvement of the one-photon miniscope method, being a potential breakthrough of this mainstream method lasting more than ten years.

A.V. Pavlov, A.O. Gaugel

A task of modeling individual mental features of a decision-maker using a Fourier holography setup is considered. The problem is considered for a situation when current conditions of decision-making contradict to the previously learned rule of decision-making logic modeled by the non-cooperative game "Prisoner's Dilemma". The approach to the problem is based on a hypothesis of the correlation between mental features and the properties of the neural network as a material carrier of intelligence. The 6f Fourier holography scheme of the resonant architecture is considered as a three-layer neural network implementing a neuro-physiologically motivated concept of the "excitation ring" proposed by A.M. Ivanitsky. We analytically assess the dependence of the validity limits of the classical total probability formula for a disjunction of incompatible events on the characteristics of low-frequency filters in holograms and the correlation radii of the training image of the basic decision rule. Analytical results are confirmed by results of the numerical simulation.

Isidore Nsengiyumva, Elijah Mwangi, George Kamucha

This paper investigates a novel compensation technique of dispersion effect mitigation using a combination of three- and four-stage-apodized fiber Bragg gratings (FBG) and dispersion compensating fiber (DCF) designs. Two designs using three-stage and four-stage FBG and DCF in combination have been proposed and compared for their performance in mitigating chromatic dispersion effects at 100 km SMF. The performance of each design has been evaluated using Q-factor results using linear Gaussian- and tanh-apodized fiber Bragg gratings. Each profile manifested different Q-factor results over a range of 5 dBm, 7.5 dBm, and 10 dBm of CW laser power over FBG grating lengths from 4 mm to 8 mm. The results obtained using the three-stage and four-stage FBG and DCF designs showed that an apodization profile using a tanh function can be used successfully with FBG lengths from 4 mm to 8 mm, regardless of the CW launched power. In contrast, the results using a Gaussian apodization profile for three- and four-stage FBG and DCF designs are applicable to FBG lengths from 5 mm to 8 mm. Designs using three-stage FBG and DCF generated higher Q-factor results than designs using only four-stage FBG and DCF, regardless of the launched power. The highest Q-factor of 18.58 was obtained for three-stage tanh-apodized FBG and DCF used in combination for an FBG length of 6 mm. The highest result obtained for a three-stage Gaussian-apodized FBG and DCF design was a Q factor of 17.13 using an FBG length of 8 mm. The proposed method was also compared to current similar works and can be successfully implemented in long-haul optical communication.

T. Bunning, L. Natarajan, V. Tondiglia et al.

Xiansheng Tang, Ziguang Ma, Wenqi Wang et al.

Photonic crystal has been proved to manipulate light effectively and improve the performance of solar cells. In this paper, high-performance GaAs-based solar cells with photonic crystal were fabricated to decrease the dependence on the angle of incident light. Photoluminescence (PL) intensity of solar cells with photonic crystal reduced only 8&#x0025; when the incident angle changed from 10&#x00B0; to 30&#x00B0;, while the PL intensity of the ordinary solar cells decreased 39&#x0025; under the same condition. It manifests the photonic crystal can manipulate the incident light in turn reduce the dependence of incident light angle. Besides, the short circuit current of solar cells was increased by 32&#x0025; after the photonic crystal was added. When the incident angle of light increased to 30&#x00B0; from 0&#x00B0;, the short circuit current of ordinary solar cell decreased 29.5&#x0025;, while that of solar cell with photonic crystals reduced 12&#x0025;. Correspondingly, the photoelectric conversion efficiency (PCE) of ordinary solar cells was reduced 31.2&#x0025;. In contrast, solar cells with photonic crystal decreased only 11.5&#x0025;. The enhancement factor of the PCE of solar cells with photonic crystal to that of ordinary solar cells increases from 1.26 to 1.6 as the incident angle rises to 30&#x00B0;from 0&#x00B0;. In summary, solar cells with photonic crystal are less sensitive to the incident angle and could absorb more light without angle limits, then increase the PCE. These solar cells with photonic crystals are promising in low-cost and high power conversion efficiency solar cell fields.

P.A. Lyakhov, U.A. Lyakhova

The article proposes a neural network classification system for pigmented skin neoplasms with a preliminary processing stage to remove hair from the images. The main difference of the proposed system is the use of the stage of preliminary image processing to identify the location of the hair and their further removal. This stage allows you to prepare dermatoscopic images for further analysis in order to carry out automated classification and diagnosis of pigmented skin lesions. Modeling was carried out using the MatLAB R2020b software package on clinical dermatoscopic images from the international open archive ISIC Melanoma Project. The proposed system made it possible to increase the recognition accuracy of pigmented skin lesion images in 10 diagnostically important categories up to 80.81%. The use of the proposed system for the recognition and classification of images of dermatoscopic pigmented lesions by specialists will make it possible to increase the diagnostic efficiency in comparison with methods of visual diagnosis, and will also allow starting treatment at an earlier stage of the disease, which directly affects the survival and recovery rates for patients.

Jonas S Neergaard-Nielsen, B. M. Nielsen, C. Hettich et al.

We report on the experimental observation of quantum-network-compatible light described by a nonpositive Wigner function. The state is generated by photon subtraction from a squeezed vacuum state produced by a continuous wave optical parametric amplifier. Ideally, the state is a coherent superposition of odd photon number states, closely resembling a superposition of weak coherent states |alpha > - |-alpha >. In the limit of low squeezing the state is basically a single photon state. Light is generated with about 10,000 and more events per second in a nearly perfect spatial mode with a Fourier-limited frequency bandwidth which matches well atomic quantum memory requirements. The generated state of light is an excellent input state for testing quantum memories, quantum repeaters, and linear optics quantum computers.

Feng Wang, Xin-lu Zhang, Jin-Hui Cui et al.

Presents corrections to byline information for the above named paper.

Linyou Cao, Pengyu Fan, E. Barnard et al.

Meng Cui, Changhuei Yang

In this work, we report a novel high capacity (number of degrees of freedom) open loop adaptive optics method, termed digital optical phase conjugation (DOPC), which provides a robust optoelectronic optical phase conjugation (OPC) solution. We showed that our prototype can phase conjugate light fields with approximately 3.9 x 10(-3) degree accuracy over a range of approximately 3 degrees and can phase conjugate an input field through a relatively thick turbid medium (micro(s)l approximately 13). Furthermore, we employed this system to show that the reversing of random scattering in turbid media by phase conjugation is surprisingly robust and accommodating of phase errors. An OPC wavefront with significant spatial phase errors (error uniformly distributed from - pi/2 to pi/2) can nevertheless allow OPC reconstruction through a scattering medium with approximately 40% of the efficiency achieved with phase error free OPC.

De Chao Ban, Qing Chao Huang, Yin Fang Chen et al.

A novel optical frequency-hopping scheme based on a flexible structure for secure optical communications is proposed and demonstrated. In the proposed scheme, critical users&#x2019; data are divided into a lot of segments, and these segments are transmitted by different optical wavelengths in time domain. In other words, one channel optical carrier carries different users&#x2019; data segments. A flexible structure was demonstrated and used in optical frequency-hopping system to simplify the structure and decrease the cost of the security system. In this paper, the viability of a four-wavelength-frequency-hopping secure optical communication system with a 25-Gb&#x002F;s error-free transmission through a 32-km single-mode fiber and a 8-km dispersion compensation fiber was demonstrated and verified by simulation tools.