The impact of enhanced local heating due to absorption of solar radiation by elevated layers of aerosol black carbon (BC) in the lower troposphere in the performance of free-space optical (FSO) communication links is investigated. It is seen that a strong elevated BC layer at an altitude around 4.5 km enhances the atmospheric stability locally and leads to a large reduction in the atmospheric refractive index structure parameter (Cn2), leading to improved performance of the FSO communication links. For layers in the tropical atmosphere with sufficiently high BC concentration, the signal attenuation due to BC absorption is alleviated by the large reduction in Cn2 due to BC-induced warming and brings down the link outage probability. Synergy between reduction in Cn2 and long wavelength transmission improves the link budget significantly by reducing the beam wander and number of adaptive optics units required.
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http://dx.doi.org/10.1364/AO.57.007152 | DOI Listing |
Nanoscale
January 2025
State Key Laboratory of Optoelectronic Materials and Technologies, School of Physics, Sun Yat-Sen University, Guangzhou 510275, China.
Hyperbolic metamaterials (HMMs) have recently attracted significant research attention due to their hyperbolic wavevector iso-frequency contour, which leads to substantial local electric field (EF) enhancements that benefit optical processes, such as the nonlinear generation, quantum science, biomedical sensing, and more. However, three main challenges hinder their practical implementation: the difficulty in exciting their resonant modes using free-space incidence, the weak enhancement of surface EF, and the narrow spectral range of EF enhancements. Herein, we proposed cross-etched HMMs (CeHMMs) as a novel type of HMM, addressing these issues.
View Article and Find Full Text PDFSmall
January 2025
CNR NANOTEC Institute of Nanotechnology, Via Monteroni, 73100, Lecce, Italy.
Photonics bound states in the continuum (BICs) are peculiar localized states in the continuum of free-space waves, unaffected by far-field radiation loss. Although plasmonic nano-antennas squeeze the optical field to nanoscale volumes, engineering the emergence of quasi-BICs with plasmonic hotspots remains challenging. Here, the origin of symmetry-protected (SP) quasi-BICs in a 2D system of silver-filled dimers, quasi-embedded in a high-index dielectric waveguide, is investigated through the strong coupling between photonic and plasmonic modes.
View Article and Find Full Text PDFSensors (Basel)
January 2025
Free-Space Optical Communication Technology Research Center, Harbin Institute of Technology, Harbin 150001, China.
To achieve real-time deep learning wavefront sensing (DLWFS) of dynamic random wavefront distortions induced by atmospheric turbulence, this study proposes an enhanced wavefront sensing neural network (WFSNet) based on convolutional neural networks (CNN). We introduce a novel multi-objective neural architecture search (MNAS) method designed to attain Pareto optimality in terms of error and floating-point operations (FLOPs) for the WFSNet. Utilizing EfficientNet-B0 prototypes, we propose a WFSNet with enhanced neural architecture which significantly reduces computational costs by 80% while improving wavefront sensing accuracy by 22%.
View Article and Find Full Text PDFSensors (Basel)
January 2025
Informatics Institute, Istanbul Technical University, 34467 Istanbul, Turkey.
In this study, we present a dual-hop decode-and-forward relaying-based free-space optical (FSO) communication system. We consider utilizing simultaneous lightwave information and power transfer (SLIPT) with a time-splitting technique at the relay, where the direct current component of the received optical signal is harvested as a transmit power for the relay. It is assumed that the FSO links experience a Malaga turbulence channel with pointing errors.
View Article and Find Full Text PDFSci Rep
January 2025
Applied Optics Laboratory, Institute of Optics and Precision Mechanics, University Setif 1, Setif, 19000, Algeria.
This prediction evaluates the different physical characteristics of magnetic materials XFeO (X = Mg, Ca and Sr) by using density functional theory (DFT). The generalized gradient approximation (GGA) approach is chosen to define the exchange and correlation potential. The structural study of the compounds XFeO (X = Mg, Ca and Sr) shows that the ferromagnetic phase is the more stable ground state, where all the parameters of the network are given at equilibrium.
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