This paper presents a two-dimensional numerical simulation performed using the Silvaco TCAD simulator to optimize the effect of a BGaN back-barrier on the performance of an InGaN-based PIN solar cell. The electrical characteristics of the device are analyzed for four different structures: (1) reference structure without BGaN and without MQWs, (2) with BGaN back-barrier only, (3) with InGaN/GaN MQWs only, and (4) with both BGaN back-barrier and MQWs. The results show that the introduction of a 100-nm-thick BGaN back-barrier layer, along with a reduction of the boron concentration to 3
This paper constructs a bidirectional air-to-ground free-space optical (FSO) link model employing the multiple phase screen method, analyzing the channel fading characteristics under the combined effects of atmospheric attenuation, atmospheric turbulence, and tracking errors. The non-uniform transmission path is discretized according to the equal Rytov variance criterion, while Zernike tilt aberrations are superimposed on the initial transmitted optical field to simulate dynamic tracking errors. The simulated beam-centroid deviation and point scintillation index are compared with theoretical results to verify the tracking-error model and determine the required number of phase screens. Based on Monte Carlo simulations, the Gaussian mixture model (GMM) was utilized to fit the received-power probability density function (PDF), and the outage probability and average bit error rate (BER) were evaluated under various tracking accuracies, flight altitudes, and zenith angles. The simulation results confirm an inherent asymmetry between the bidirectional links, as the uplink exhibits significantly higher outage probability and BER than the downlink, necessitating higher transmit power to maintain equivalent communication reliability.
Luminescent down-shifting (LDS) nanocomposite films based on polycarbonate (PC) doped with cadmium sulfide nanocrystals (CdS NCs) were developed and evaluated as spectral-conversion coatings for multicrystalline silicon (mc-Si) photovoltaic cells intended for façade applications. The films were characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), optical absorption, transmission, fluorescence spectroscopy, and CIE 1976 color measurements. XRD confirmed the hexagonal wurtzite phase of the CdS NCs. The CdS@PC films absorb near-ultraviolet radiation at approximately 390 nm and re-emit it at around 530 nm, where the emission overlaps strongly with the spectral response of mc-Si photovoltaic cells and the photopic sensitivity of the human eye. Films containing up to 3 wt
The development of compact, low-loss, and robust waveguides is a critical requirement for next-generation integrated photonic circuits. Line waves (LWs), as highly confined one-dimensional electromagnetic modes, offer a promising platform for addressing this need. However, practical implementation of LW-based devices is hindered by propagation losses and sensitivity to structural imperfections. In this work, we introduce a class of gain-assisted non-Hermitian metasurfaces that preserve the electromagnetic-duality conditions required for LW formation while enabling controlled loss compensation and modal amplification. By engineering the real and reactive parts of the impedance boundaries, we demonstrate that the propagation characteristics of the guided modes can be tuned from lossy to weakly amplifying regimes. The proposed platform is further investigated for LW-like modes, coupled line-wave configurations, and bent waveguides, where gain-assisted impedance engineering can compensate propagation losses. The directional behaviour considered here originates from pseudospin-dependent propagation and spin-momentum locking in the reciprocal structure, rather than from nonreciprocal isolation. In addition, an LW-based Mach–Zehnder interferometric architecture is investigated as a tuneable sensing platform. Full-wave simulations are performed using ANSYS HFSS to characterize the field confinement, transmission response, dispersion, and propagation characteristics. The results demonstrate the potential of gain-assisted non-Hermitian impedance engineering for compact and reconfigurable waveguiding, sensing, and feeding-network applications, while practical implementation requires causal dispersive active metasurfaces with finite gain bandwidth and stable operation.
Many strategies have been proposed to manipulate and protect symmetric quantum correlations against decoherence. However, more research is needed to focus on asymmetric correlations, such as quantum steering. To address this gap, we investigate the dynamics of quantum steering between two moving qubits within separate cavities. Specifically, we explore how the qubits’ velocity impacts the dynamics of quantum steering. The results indicate that when each qubit interacts independently with its cavity, increasing its velocity can enhance quantum steering, regardless of whether the dynamics is Markovian or non-Markovian. We also find that the qubits’ motion can effectively control the asymmetric nature of steering even when symmetric environmental noise acts on an initially asymmetric mixed state. Furthermore, we analyze the asymmetric properties of quantum steering by considering a scenario in which one qubit remains stationary in its cavity. The findings show that adjusting the velocity of the moving qubit can efficiently manipulate asymmetric properties, such as “one-way” and “two-way” steering, thereby enhancing quantum steering and manipulating its asymmetry without consuming external quantum resources in the cavities.
