Browsing by Author "Serebryannikov, Andriy E."

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Open Access
Correction to: Active tuning from narrowband to broadband absorbers using a sub-wavelength VO2 embedded layer
(Springer, 2021-02-04) Osgouei, Ataollah Kalantari; Hajian, Hodjat; Khalichi, Bahram; Serebryannikov, Andriy E.; Ghobadi, Amir; Özbay, Ekmel
Metamaterial perfect absorbers (MPAs) with dynamic thermal tuning features are able to control the absorption performance of the resonances, providing diverse applications spanning from optical switches and filters to modulators. In this paper, we propose an MPA with diverse functionalities enabled by vanadium dioxide (VO2) embedded in a metal-dielectric plasmonic structure. For the initial design purpose, a silicon (Si) nanograting on a silver (Ag) mirror is proposed to have multiple resonant responses in the near infrared (NIR) region. Then, the insertion of a thin VO2 layer at the right position enables the design to act as an on/off switch and resonance tuner. In the insulator phase of VO2, in which the permittivity data of VO2 is similar to that of Si, a double strong resonant behavior is achieved within the NIR region. By increasing the temperature, the state of VO2 transforms from insulator to metallic so that the absorption bands turn into three distinct resonant peaks with close spectral positions. Upon this transformation, a new resonance emerges and the existing resonance features experience blue/red shifts in the spectral domain. The superposition of these peaks makes the overall absorption bandwidth broad. Although Si has a small thermo-optic coefficient, owing to strong light confinement in the ultrasmall gaps, a substantial tuning can be achieved within the Si nanogratings. Therefore, the proposed hybrid design can provide multi-resonance tunable features to cover a broad range and can be a promising strategy for the design of linearly thermal-tunable and broadband MPAs. Owing to the proposed double tuning feature, the resonance wavelengths exhibits great sensitivity to temperature, covering a broad wavelength range. Overall, the proposed design strategy demonstrates diverse functionalities enabled by the integration of a thin VO2 layer with plasmonic absorbers.
Open Access
Evidence of asymmetric beaming in a piecewise-linear propagation channel
(Optica, 2021-06) Gündoğdu, Tamara Funda; Gökkavas, Mutlu; Serebryannikov, Andriy E.; Özbay, Ekmel
Asymmetric beaming in a piecewise-linear propagation channel is demonstrated for a single photonic-crystal prism at Gaussian-beam illumination. The used hybrid refraction– diffraction mechanism exploits oblique incidence, the first-negative-order deflection at the longer interface, and asymmetry in coupling at the exit interfaces and does not need blocking of transmission by dispersion in the back ward illumination case. The Floquet–Bloch mode with left-handed behavior and nearly circular equifrequency dis persion contours is utilized. The outgoing waves may have significantly different spatial distributions for the forward and backward illumination cases, yielding asymmetry in the beaming regime.
Open Access
Hybrid indium tin oxide-Au metamaterial as a multiband bi-functional light absorber in the visible and near-infrared ranges
(2021-04-23) Osgouei, Ataollah Kalantari; Hajian, Hodjat; Serebryannikov, Andriy E.; Özbay, Ekmel
Metamaterial nearly perfect light absorbers (MPAs) with dual-narrowband functionality—that absorb light in two narrowband adjacent wavelength regions—have attracted considerable attention due to their intriguing applications, such as sensing, photovoltaic, and thermal emission. Here, we propose a multi-band MPA with two narrowband absorption responses that are centered on the visible and near-infrared (NIR) wavelengths (773 nm and 900 nm, respectively) and a broadband absorptive characteristic in another window in the NIR region (ranging from 1530 nm to 2700 nm with a bandwidth of 1170 nm). The MPA comprises a periodic array of self-aligned hybrid indium tin oxide (ITO)-Au split-ring-resonators that are separated from an optically thick bottom reflector with a SiO2 layer. Based on numerical calculations, which are accompanied with a semi-analytical examination, we find that the dual narrowband and broadband responses are attributed to the hybridization of the optical responses of gold as a plasmonic material with the ones of ITO. Note that ITO acts as a low-loss dielectric in the visible range and a lossy plasmonic material in the NIR region. Moreover, due to the applied symmetry in the unit cell of the metamaterial, the proposed MPA represents polarization insensitive and omnidirectional absorptive features. The proposed metastructure can find potential applications in selective thermophotovoltaic devices, thermal emitters, and sensors.
Open Access
Multifunctional tunable gradient metasurfaces for terahertz beam splitting and light absorption
(Optica, 2021-08-15) Erçağlar, Veysel; Hajian, Hodjat; Serebryannikov, Andriy E.; Özbay, Ekmel
Obtaining functional devices with tunable features is benefi cial to advance terahertz (THz) science and technology. Here, we propose multifunctional gradient metasur faces that are composed of a periodic array of binary Si microcylinders integrated with VO2 and graphene. The metasurfaces act as transmittive (reflective) beamsplitters for the dielectric (metallic) phase of VO2 with a switchable characteristic. Moreover, by integrating the metasurfaces with graphene and modifying its chemical potential, one can tune the intensity of the split beam as well as obtain nearly perfect resonant absorptions. Consequently, the proposed metasurfaces can find potential applications in THz interferometers, multiplexers, and light absorbers.
Open Access
One-way and near-absolute polarization insensitive near-perfect absorption by using an all-dielectric metasurface
(OSA - The Optical Society, 2020) Yıldırım, Deniz Umut; Ghobadi, Amir; Soydan, Mahmut Can; Serebryannikov, Andriy E.; Özbay, Ekmel
In this Letter, we numerically propose the one-way perfect absorption of near-infrared radiation in a tunable spectral range with high transmission in the neighboring spectral ranges. This functionality is obtained by using a two-dimensional, guided-mode resonance-based grating-waveguide metasurface that acts as a frequency-selective reflector, a spacer dielectric, and an absorbing oxide layer. Within the bandwidth of the excited guided-mode resonance excited at 1.82 µm (with a full-width at half-maximum of 19 nm), we confirmed perfect absorption when light was incident from one of the two opposite directions, whereas in the other direction, perfect reflection was observed. The forward-to-backward absorption ratio reached as high as 60, while the thickness of the entire structure was on the order of the operating wavelength. In addition to the spectral tunability of the excited resonances and their bandwidths, our proposed device supports transparency windows with 65% transmission in the adjacent frequency bands. Our 2D grating is also verified to enable near-absolute insensitivity to the polarization state of incident light. Geometrical parameter modification also gives our design great tunability, as we also designed a device with a 300 nm absorption/reflection linewidth.
Open Access
Photonic Crystal based spatial filtering
(IEEE, 2009) Colak, E.; Çakmak, A. Özgür; Serebryannikov, Andriy E.; Özbay, Ekmel
Two dimensional Photonic Crystal structure is used to achieve spatial filtering. The structure provides bandstop filtering in the incident angle range of 18° to 38°. The transmission is close to unity outside of this range. © 2009 IEEE.
Open Access
Thermally switchable, bifunctional, scalable, mid-infrared metasurfaces with VO2 grids capable of versatile polarization manipulation and asymmetric transmission
(Optica Publishing Group (formerly OSA), 2022-12-01) Serebryannikov, Andriy E.; Lakhtakia, Akhlesh; Özbay, Ekmel
We conceptualized three-array scalable bifunctional metasurfaces comprising only three thin strip grids and numerically determined their characteristics in the mid-infrared spectral regime for switchable operation scenarios involving polarization manipulation and related diodelike asymmetric transmission (AT) as one of two functionalities. A few or all of the grids were taken to be made of VO2, a bifunctionality-enabling phase-change material; there are no layers and/or meta-atoms comprising simultaneously both metal and VO2. For each proposed metasurface, two effective structures and, therefore, two different functionalities exist, corresponding to the metallic and insulating phases of VO2. The achieved scenarios of functionality switching significantly depend on the way in which VO2 is incorporated into the metasurface. Switchable bands of polarization manipulation are up to 40 THz wide. The AT band can be modulated when Fabry-Perot (anti-) resonances come into play. Besides, transmission regimes with the cross-polarized component insensitive to VO2 phase change are possible, as well as the ones with all co- and cross-polarized components having the same magnitude for both linear polarizations of the incident wave. © 2022 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement.
Open Access
Transmissive terahertz metasurfaces with vanadium dioxide split-rings and grids for switchable asymmetric polarization manipulation
(Nature Research, 2022-12) Serebryannikov, Andriy E.; Lakhtakia, Akhlesh; Vandenbosch, Guy A. E.; Özbay, Ekmel
Metasurfaces containing arrays of thermally tunable metal-free (double-)split-ring meta-atoms and metal-free grids made of vanadium dioxide (VO2), a phase-change material can deliver switching between (1) polarization manipulation in transmission mode as well as related asymmetric transmission and (2) other functionalities in the terahertz regime, especially when operation in the transmission mode is needed to be conserved for both phases of VO2. As the meta-atom arrays function as arrays of metallic subwavelength resonators for the metallic phase of VO2, but as transmissive phase screens for the insulator phase of VO2, numerical simulations of double- and triple-array metasurfaces strongly indicate extreme scenarios of functionality switching also when the resulting structure comprises only VO2 meta-atoms and VO2 grids. More switching scenarios are achievable when only one meta-atom array or one grid is made of VO2 components. They are enabled by the efficient coupling of the geometrically identical resonator arrays/grids that are made of the materials that strongly differ in terms of conductivity, i.e. Cu and VO2 in the metallic phase. © 2022, The Author(s).
Open Access
Wide-angle and simultaneously wideband blazing (deflection) enabling multifunctionality in metagratings comprising epsilon-near-zero materials
(Optica Publishing Group (formerly OSA), 2023-05-01) Serebryannikov, Andriy E.; Skigin, Diana C.; Hajian, Hodjat; Özbay, Ekmel
This paper investigates diffractions by gratings made of a dispersive material in an epsilon-near-zero (ENZ) regime and having one-side corrugations, and those by two-component dielectric-ENZ gratings with the inner corrugations and flat outer interfaces. The goal is to achieve wideband and simultaneously wide-angle −1st order blazing (deflection) that may enable wideband spatial filtering and demultiplexing in reflection mode. Several typical scenarios are discussed, which differ in the maximum magnitude of the blazed wave and size of the blazing area observed on the frequency-incidence angle plane, as well as the contribution of the ranges of positive and negative permittivity in the vicinity of zero. The high capability of ENZ and dielectric-ENZ gratings in asymmetric reflection is demonstrated for three different levels of losses for the dispersive material.