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In recent research, there has been a significant focus on establishing robust quantum cryptography using the continuous-variable quantum key distribution (CV-QKD) protocol based on Gaussian modulation of coherent states (GMCS). Unlike more stable fiber channels, one challenge faced in free-space quantum channels is the complex transmittance characterized by varying atmospheric turbulence. This complexity poses difficulties in achieving high transmission rates and long-distance communication. In this article, we thoroughly evaluate the performance of the CV-QKD/GMCS system under the effect of individual attacks, considering homodyne detection with both direct and reverse reconciliation techniques. To address the issue of limited detector efficiency, we incorporate the phase-sensitive amplifier (PSA) as a compensating measure. The results show that the CV-QKD/GMCS system with PSA achieves a longer secure distance and a higher key rate compared to the system without PSA, considering both direct and reverse reconciliation algorithms. With an amplifier gain of 10, the reverse reconciliation algorithm achieves a secure distance of 5 km with a secret key rate of 10-1 bits/pulse. On the other hand, direct reconciliation reaches a secure distance of 2.82 km.
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This paper investigates the improvement of energy conversion efficiency in thin-film silicon solar cells by employing periodic nanostructures of T i O 2 on the silicon active layer and a back reflector featuring periodic nanostructures of silver. The objective is to increase the optical path length, enhance absorption probability for longer wavelengths, and subsequently improve solar cell performance. Three silicon-based solar cell configurations are proposed and simulated using the finite difference time domain (FDTD) method to assess their performance. Electrical characteristics are obtained through the drift-diffusion method. The resulting short-circuit current density increased from 40.93 to 65.28 to 95.373m A/c m 2 for the three cells, leading to significant improvements in conversion efficiency with observed values of 20.39%, 33.26%, and 47.28%, respectively, in the optimized structures. Furthermore, we compare the simulation results of the three structures with those of a reference structure and several structures previously proposed in the literature.
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This study presents the design and characterization of a highly Q-Factor and ultrasensitive THz refractive-index-based metamaterial biosensor for detecting coronaviruses at electronic infusion device (EID) concentrations 0.01 and 1000. The proposed biosensor is constructed using a gold plane perforated by a star shape. Moreover, the developed structure is polarization insensitive due to the rotatory symmetry and is angularly stable up to 90°. The proposed biosensor achieves near-perfect absorption at 1.9656 THz and 3.3692 THz. The full width at half-maximum is 5.276% and 0.641% comparative to the absorption frequency. In addition, the estimated free space absorptivity is 97.2% and 99.1% with a Q-Factor of 19.08 and 155.98 at 1.9656 THz and 3.3692 THz, respectively, when transverse electromagnetic mode (TEM) was selected. The perforated star-shaped was evaluated for IBV (Family of COVID-19) regarding frequency deviation, sensitivity, and figure of merit. Results show that at 1.9656 THz, the proposed design gives 30.8 GHz, 940.49 GHz/RIU, and 8.6, respectively, for 0.01 (EID/5 µL concentration) and 4.4 GHz, 2200 × 103 GHz/RIU, and 20,215.014, respectively at 1.9612 THz for 1000 (EID/5 µL concentration). Although the obtained results demonstrate the efficiency of the proposed THz metamaterial biosensor in coronavirus detection, it has also been extended for other types of viruses, including H5N1, H5N2, H9N2, H4N6, and FAdV, based on the slight variations in their refractive indices. Additionally, the influence of the design parameters is optimized in order to achieve better performance.
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Organic photovoltaic research is continuing in order to improve the efficiency and stability of the products. Organic devices have recently demonstrated excellent efficiency, bringing them closer to the market. Understanding the relationship between the microscopic parameters of the device and the conditions under which it is prepared and operated is essential for improving performance at the device level. This review paper emphasizes the importance of the parameter extraction stage for organic solar cell investigations by offering various device models and extraction methodologies. In order to link qualitative experimental measurements to quantitative microscopic device parameters with a minimum number of experimental setups, parameter extraction is a valuable step. The number of experimental setups directly impacts the pace and cost of development. Several experimental and material processing procedures, including the use of additives, annealing, and polymer chain engineering, are discussed in terms of their impact on the parameters of organic solar cells. Various analytical, numerical, hybrid, and optimization methods were introduced for parameter extraction based on single, multiple diodes and drift-diffusion models. Their validity for organic devices was tested by extracting the parameters of some available devices from the literature.