Browsing by Author "Omam, Zahra Rahimian"

Now showing 1 - 7 of 7

Open Access
Adaptive thermal camouflage using sub-wavelength phase-change metasurfaces
(Institute of Physics Publishing Ltd., 2022-12-09) Omam, Zahra Rahimian; Ghobadi, Amir; Özbay, Ekmel; Khalichi, Bahram
Sub-wavelength metasurface designs can be used to artificially engineer the spectral thermal signature of an object. The real-time control of this emission can provide the opportunity to switch between radiative cooling (RC) and thermal camouflage functionalities. This performance could be achieved by using phase-change materials (PCMs). This paper presents a sub-wavelength dynamic metasurface design with the adaptive property. The proposed metasurface is made of vanadium dioxide (VO2) nanogratings on a silver (Ag) substrate. The design geometries are optimized in a way that both narrowband and broadband mid-infrared (MIR) emitters can be realized. At low temperatures, insulating VO2 nanogratings trigger the excitation of Fabry–Perot mode inside the grating and surface plasmon polaritons at the metal–dielectric interface with an emission peak located in the MIR region to maximize the RC performance of the design. As temperature rises, the PCM transforms into a metallic phase material and supports excitation of Wood's anomaly and localized surface plasmon resonance modes. Accordingly, the thermal signature is adaptively suppressed.
Open Access
Disordered plasmonic nanocavity enhanced quantum dot emission
(Institute of Physics, 2023-08-31) Kosger, Ali Cahit; Ghobadi, Amir; Omam, Zahra Rahimian; Soydan, Mahmut Can; Ulusoy Ghobadi, Türkan Gamze; Özbay, Ekmel
In this paper, a large-scale compatible plasmonic nanocavity design platform is utilized to achieve a nearly order of magnitude photoluminescence (PL) enhancement. The proposed design is made of multi-sized/multi-spacing gold (Au) nanounits that are uniformly wrapped with a thin aluminum oxide (Al2O3) layer, as a foreign host to form a metal-insulator-semiconductor cavity, as they are coated with semiconductor quantum dots (QDs). Our numerical and experimental data demonstrate that, in an optimal insulator layer thickness, the simultaneous formation of broadband Fabry-Perot resonances and plasmonic hot spots leads to enhanced light absorption within the QD unit. This improvement in absorption response leads to the PL enhancement of QDs. This work demonstrates the potential and effectiveness of a random plasmonic nanocavities host in the realization of lithography-free efficient emitters. © 2023 IOP Publishing Ltd
Open Access
Highly one-way electromagnetic wave transmission based on outcoupling of surface plasmon polaritons to radiation modes
(Institute of Electrical and Electronics Engineers, 2022-09-21) Khalichi, Bahram; Omam, Zahra Rahimian; Osgouei, Ataollah Kalantari; Ghobadi, Amir; Özbay, Ekmel
Unidirectional transmission of electromagnetic waves has attracted great interest due to its wide modern optical applications. This study theoretically demonstrates a one-way transmissive optical device with a high-contrast forward-to-backward ratio at the near-infrared region. The polarization-independent optical diode-like mechanism is designed using a metasurface diffraction grating configuration with symmetry breaking property along the wave propagation in which the working principle is based on the excitation of surface plasmon modes at the interfaces of thin metallic interlayer and their coupling to the radiation modes.
Open Access
Multi-band light-matter interaction in hBN-based metasurface absorber
(Institute of Electrical and Electronics Engineers, 2022-09-28) Omam, Zahra Rahimian; Khalichi, Bahram; Osgouei, Ataollah Kalantari; Ghobadi, Amir; Özbay, Ekmel
This paper presents a multi-band metamaterial-based absorber using phononic two-dimensional (2D) material. The structure consists of a top hexagonal boron nitride (hBN) layer on an aluminum nanograting structure deposited on a dielectric slab waveguide and a thick metallic reflector forming an MIM (metal-insulator-metal) configuration. The proposed absorber exhibits a hyperbolic phonon polariton (HPPs) in hBN, surface plasmon (SP) modes in the spacer (ZnTe: zinc telluride), and Fabry-Perot resonances in the MIM configuration, resulting in five sharp, high absorption peaks in the mid-infrared (MIR) spectral range. The proposed multi-band absorber can be utilized in various applications, ranging from optical detection devices to multispectral thermoelectric volt.
Open Access
Polarization insensitive phase change material-based nanoantenna array for thermally tunable infrared applications
(Institute of Electrical and Electronics Engineers, 2022-09-21) Khalichi, Bahram; Omam, Zahra Rahimian; Osgouei, Ataollah Kalantari; Ghobadi, Amir; Özbay, Ekmel
Thermal radiation management is an emerging application of metamaterials owing to their exotic electromagnetic radiative properties. Herein, a thermally tunable phase change material-based nanoantenna array is reported to manipulate electromagnetic waves for potential applications in radiative cooling and multispectral camouflage from thermal infrared detectors. The simulation results show that the proposed nanoantenna array possesses high reflectance exceeding at least 60% within the 3−5 µm and 8−12 µm wavelength ranges, indicating low thermal emissivity, while the reflectance value increases as the temperature rises. Additionally, the wavelength-selective nanoantenna emitter operates with high absorption and therefore emission within the non-atmospheric window (5−8 µm). The thermally tuning feature leads to further controlling the absorption and, therefore, the emission performance of the nanoantenna and corresponding infrared signatures detected by thermal cameras.
Open Access
A Transmissive all-dielectric metasurface-based nanoantenna array for selectively manipulation of thermal radiation
(Institute of Electrical and Electronics Engineers, 2022-09-21) Khalichi, Bahram; Omam, Zahra Rahimian; Osgouei, Ataollah Kalantari; Ghobadi, Amir; Özbay, Ekmel
In this study, a wavelength-selective thermal nanoantenna emitter based on metamaterial design with heat radiation signature management and radiative cooling property is proposed. The design can be considered as a multifunctional window by reducing the heat signature and releasing the heat energy within the non-atmospheric window. The approach relies on the indium tin oxide cubic-shaped unit cell coated on a flexible and transparent substrate (polystyrene). The spectral behaviors of the proposed structure are obtained using the finite difference time domain method, where the power calculation model is utilized to demonstrate the radiative cooling efficiency and low power detection on infrared cameras.
Open Access
A wavelength-selective multilayer absorber for heat signature control
(Institute of Electrical and Electronics Engineers, 2022-09-28) Osgouei, Ataollah Kalantari; Khalichi, Bahram; Omam, Zahra Rahimian; Ghobadi, Amir; Özbay, Ekmel
Engineering the thermal radiation using wavelength-selective thermal emitters is of great importance in the field of thermophotovoltaics, radiative cooling, and heat signature control. In this paper, a wavelength-selective Vanadium/Germanium (V/Ge) multilayer absorber is demonstrated. The proposed design realizes a perfect absorption at the resonance wavelength of 5870 nm, placed within the nonatmospheric window (5-8 μ m) while maintaining low absorptivity within the atmospheric windows. It is verified that the proposed emitter represents angle insensitive feature for oblique incidence up to 60° for both transverse magnetic (TM) and transverse electric (TE) polarizations.