Distributed Bragg reflectors (DBRs) have been developed as an effective way for reflecting light in several applications. In this work, a cavity medium is introduced between the DBR and substrate to increase the reflection by stimulating the cavity modes. The DBR has been designed carefully based on the quarter-wavelength rule utilizing the transfer matrix method (TMM). The thickness, number of layers, and material composition have been optimized, and the surface reflectance of a DBR-coated substrate with and without a cavity layer is compared. Employing FDTD simulations, the optimal thickness of the cavity layer for the incident wavelength of the interest is obtained. The results show a significant enhancement in the reflection by introducing the cavity in the design.
Vanadium dioxide (VO2) exhibits reversible insulator-to-metal phase transition at 68°C, making it promising for diverse applications. However, its low thermal stability in the metallic phase and insufficient emissivity in the near-mid infrared range limit practical use. To address these challenges, we propose a core-shell structure deposited on a metal layer. This configuration enhances VO2's optical properties in both phases, facilitating efficient absorption and reflection of near-infrared radiation.
Passive radiative cooling has garnered significant attention in recent years due to its potential in addressing the energy consumption of conventional cooling systems. Plasmonic and metamaterial structures have been found to be effective broadband absorbers due to their selective emissive spectra, thin thickness, design flexibility, and the ability to excite plasmonic or photonic resonances. This study explores the use of bowtie shape plasmonic metamaterials for the development of novel, structurally simple radiative cooling devices. We show that by designing and optimizing a periodic high index-low index alternating layers (SiO2-TiO2), broadband reflection in visible and near-infrared spectrums is achievable. While to achieve broadband absorption in the transparency window (8-13 um), metamaterial is utilized.
Carrier distribution of semiconductors (SCs) differs from metals where they can give inhomogeneous carrier distributions like the classical Schottky junction. In this study, we show that the carrier distribution at a moderately doped semiconductor – dielectric (DE) interface can be tuned by applying external voltage, and then an inhomogeneous permittivity. Using the Maxwell’s equations for doped semiconductor surfaces, we illustrate the voltage controlled tunability of plasmon and phonon polaritons.
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