BUIR Repository :: Browsing by Author "Ghobadi, Amir"

Browsing by Author "Ghobadi, Amir"

Now showing 1 - 20 of 68

Open Access
Active metamaterial nearly perfect light absorbers: A review [Invited]
(Optical Society of America, 2019) Hajian, Hodjat; Ghobadi, Amir; Bütün, Bayram; Özbay, Ekmel
Achieving nearly perfect light absorption from the microwave to optical region utilizing metamaterials has begun to play a significant role in photonics and optoelectronics due to their vital applications in thermal emitters, thermal photovoltaics, photovoltaics, sensing, filtering, and photodetection. However, employing passive components in designing perfect absorbers based on metamaterials and photonic crystals imposes some limits on their spectral operation. In order to overcome those limits, extensive research has been conducted on utilizing different materials and mechanisms to obtain active metamaterial light absorbers. In this review paper, we investigate the recent progress in tunable and reconfigurable metamaterial light absorbers through reviewing different active materials and mechanisms, and we provide a perspective for their future development and applications.
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
Adaptive thermally tunable radiative cooling with angle insensitivity using phase-change-material-based metasurface
(Institute of Physics Publishing Ltd., 2023-11-17) Boşdurmaz, Ekin Bircan; Ghobadi, Amir; Özbay, Ekmel
Radiative cooling is the passive cooling of a material with the help of a specific spectral response to emit thermal energy into space through atmospheric transparency windows. However, most of the proposed designs have no dynamically tunable emission response. In this paper, we present a feasible inverse pyramid structure made of a phase change material (PCM) on top of a metallic mirror to realize an adaptive radiative cooler with almost angle-independent emission response. The design uses the thermally controlled PCM called Samarium nickelate (SmNiO3) to actively tune the spectral response of the design, which, in turn, allows the design to radiatively cool itself. The emission response of the design is compatible with atmospheric transmissive windows. As the design heated up to higher temperatures, the peak of the emission spectrum red-shifts and moves toward the atmospheric transparency window.
Open Access
Adaptive visible and short-wave infrared camouflage using a dynamically tunable metasurface
(Optica, 2021-10-01) Buhara, Ebru; Ghobadi, Amir; Özbay, Ekmel
In this Letter, a dynamically tunable metasurface, which is based on antimony trisulfide, is introduced. In this struc ture, first a metal-insulator-metal (MIM) nanocavity is optimized in a way that, upon phase change, the visible response switches from a transmissive colored window into a reflective mirror. Later, an indium tin oxide nanoantenna is integrated on the MIM cavity to provide antireflection in the short-wave infrared (SWIR) range for SWIR mode ther mal camouflage. The MIM host acts as a thermally tunable substrate to tune the SWIR response of the design.
Open Access
All ceramic-based metal-free ultra-broadband perfect absorber
(Springer, 2019-06) Soydan, Mahmut Can; Ghobadi, Amir; Yıldırım, Deniz Umut; Ertürk, Vakur Behçet; Özbay, Ekmel
In this paper, we scrutinize unprecedented potential of transition metal carbides (TMCs) and nitrides (TMNs) for realization of light perfect absorption in an ultra-broad frequency range encompassing all of the visible (Vis) and near infrared (NIR) regions. For this purpose, two different configurations which are planar and trapezoidal array are employed. To gain insight on the condition for light perfect absorption, a systematic modeling approach based on transfer matrix method (TMM) is firstly utilized. Our modeling findings prove that the permittivity data of these TMCs and TMNs are closely matched with the ideal data. Thus, they can have stronger and broader absorption behavior compared to metals. Besides, these ceramic materials are preferred to metals due to the fact that they have better thermal properties and higher durability against erosion and oxidation than metals. This could provide the opportunity for design of highly efficient light harvesting systems with long-term stability. Numerical simulations are conducted to optimize the device optical performance for each of the proposed carbides and nitrides. Our findings reveal that these ceramic coatings have the broadest absorption response compared to all lossy and plasmonic metals. In planar configuration, titanium carbide (TiC) has the largest absorption bandwidth (BW) where an absorption above 0.9 is retained over a broad wavelength range of 405–1495 nm. In trapezoid architecture, vanadium nitride (VN) shows the widest BW covering a range from 300 to 2500 nm. The results of this study can serve as a beacon for the design of future high-performance energy conversion devices including solar vapor generation and thermal photovoltaics where both optical and thermal requirements can be satisfied.
Open Access
An all-dielectric metasurface coupled with two-dimensional semiconductors for thermally tunable ultra-narrowband light absorption
(Springer, 2020) Buhara, Ebru; Ghobadi, Amir; Özbay, Ekmel
Two-dimensional (2D) transition metal dichalcogenides (TMDCs) have attracted tremendous attention over the past decades. Due to their unique features such as high mobility and direct bandgap, they are suitable candidate for the optoelectronic devices. However, due to their ultrathin thickness, their optical absorption is quite weak, and therefore, a trapping scheme for strong light- matter interaction is essential to overcome this deficiency. To accomplish strong light absorption, loss-less dielectric-based metasurfaces with ideally no parasitic absorption are excellent choices. Herein, we report an ultra-narrowband thermally tunable all-dielectric metasurface coupled absorber with TMD monolayer. In this proposed structure, high absorption with ultra-narrow full-width-at-half-maximum (FWHM) is achieved. Different design configurations are studied to find the most suitable structure. In the optimized design, an absorptance as high as 0.85 with a FWHM of 3.1 nm is achieved. This structure also shows thermal sensitivity of 0.0096 nm/°C, without the use of any phase change material component. This architecture can be used as a 2D and highly efficient tunable single-color photodetector. The proposed dielectric metasurface can be adopted for other types of 2D and ultrathin semiconductor-based optoelectronics.
Open Access
Angstrom thick ZnO passivation layer to improve the photoelectrochemical water splitting performance of a TiO 2 nanowire photoanode: The role of deposition temperature
(Nature Publishing Group, 2018) Ghobadi, Amir; Ulusoy-Ghobadi, Türkan Gamze; Karadaş, Ferdi; Özbay, Ekmel
In this paper, we demonstrate that angstrom thick single atomic layer deposited (ALD) ZnO passivation can signifcantly improve the photoelectrochemical (PEC) activity of hydrothermally grown TiO2 NWs. It is found that this ultrathin ZnO coating can passivate the TiO2 surface defect states without hampering the carrier’s transfer dynamics. Moreover, a substantial improvement can be acquired by changing the deposition temperature of the ZnO layer (80°C, and 250°C) and named as 80°C TiO2-ZnO, and 250°C TiO2-ZnO. It was found that the deposition of this single layer in lower temperatures can lead to higher PEC activity compared to that deposited in higher ones. As a result of our PEC characterizations, it is proved that photoconversion efciency of bare TiO2 NWs can be improved by a factor of 1.5 upon coating it with a single ZnO layer at 80°C. Moreover, considering the fact that this layer is a passivating coating rather than a continuous layer, it also keeps the PEC stability of the design while this feature cannot be obtained in a thick shell layer case. This paper proposes a bottom up approach to control the electron transfer dynamics in a heterojunction design and it can be applied to other metal oxide combinations.
Open Access
Bismuth plasmonics for extraordinary light absorption in deep sub-wavelength geometries
(OSA - The Optical Society, 2020) Özbay, İ.; Ghobadi, Amir; Bütün, Bayram; Turhan-Sayan, G.
In this Letter, we demonstrate an ultra-broadband metamaterial absorber of unrivaled bandwidth (BW) using extraordinary optical response of bismuth (Bi), which is the material selected through our novel analysis. Based on our theoretical model, we investigate the maximum metal–insulator–metal (MIM) cavity BW, achievable by any metal with known n-k data. We show that an ideal metal in such structures should have a positive real permittivity part in the near-infrared (NIR) regime. Contrary to noble and lossy metals utilized by most research groups in the field, this requirement is satisfied only by Bi, whose data greatly adhere to the ideal material properties predicted by our analysis. A Bi nanodisc-based MIM resonator with an absorption above 0.9 in an ultra-broadband range of 800 nm–2390 nm is designed, fabricated, and characterized. To the best of our knowledge, this is the broadest absorption BW reported for a MIM cavity in the NIR with its upper-to-lower absorption edge ratio exceeding best contenders by more than 150%. According to the findings in this Letter, the use of proper materials and dimensions will lead to realization of deep sub-wavelength efficient optical devices.
Open Access
Bismuth-based metamaterials: From narrowband reflective color filter to extremely broadband near perfect absorber
(De Gruyter, 2019) Ghobadi, Amir; Hajian, Hodjat; Gökbayrak, Murat; Bütün, Bayram; Özbay, Ekmel
In recent years, sub-wavelength metamaterials-based light perfect absorbers have been the subject of many studies. The most frequently utilized absorber configuration is based on nanostructured plasmonic metals. However, two main drawbacks were raised for this design architecture. One is the fabrication complexity and large scale incompatibility of these nano units. The other one is the inherent limitation of these common metals which mostly operate in the visible frequency range. Recently, strong interference effects in lithography-free planar multilayer designs have been proposed as a solution for tackling these drawbacks. In this paper, we reveal the extraordinary potential of bismuth (Bi) metal in achieving light perfect absorption in a planar design through a broad wavelength regime. For this aim, we adopted a modeling approach based on the transfer matrix method (TMM) to find the ideal conditions for light perfect absorption. According to the findings of our modeling and numerical simulations, it was demonstrated that the use of Bi in the metal-insulator-metal-insulator (MIMI) configuration can simultaneously provide two distinct functionalities; a narrow near unity reflection response and an ultra-broadband near perfect absorption. The reflection behavior can be employed to realize additive color filters in the visible range, while the ultra-broadband absorption response of the design can fully harvest solar irradiation in the visible and near infrared (NIR) ranges. The findings of this paper demonstrate the extraordinary potential of Bi metal for the design of deep sub-wavelength optical devices.
Open Access
Colorimetric and near-absolute polarization-insensitive refractive-index sensing in all-dielectric guided-mode resonance based metasurface
(American Chemical Society, 2019) Yıldırım, Deniz Umut; Ghobadi, Amir; Soydan, Mahmut Can; Gökbayrak, Murat; Toprak, Ahmet; Bütün, Bayram; Özbay, Ekmel
Colorimetric detection of target molecules with insensitivity to incident-light polarization has attracted considerable attention in recent years. This resulted from the ability to provide rapid output and reduced assay times as a result of color changes upon altering the environment that are easily distinguishable by the naked eye. In this paper, we propose a highly sensitive refractive-index sensor, utilizing the excitation of guided modes of a novel two-dimensional periodically modulated dielectric grating-waveguide structure. The optimized nanosensor can numerically excite guided-mode resonances with an ultranarrow linewidth (full width at half-maximum) of 0.58 nm. Sensitivity is numerically investigated by considering the deposition of dielectric layers on the structure. For a layer thickness of 30 nm, the maximum sensitivity reached as high as 110 nm/refractive index unit (RIU), resulting in a very high figure of merit of 190. The fabricated devices with 30 nm aluminum oxide and zinc oxide coatings achieved a maximum sensitivity of 235.2 nm/RIU with a linewidth of 19 nm. Colorimetric detection with polarization insensitivity is confirmed practically by a simple optical microscope. Samples with different coatings have been observed to have clearly distinct colors, while the color of each sample is nearly identical upon azimuthal rotation. Excellent agreement is obtained between the numerical and experimental results regarding the spectral position of the resonances and sensitivity. The proposed device is, therefore, highly promising in efficient, highly sensitive, almost lossless, and compact molecular diagnostics in the field of biomedicine with personalized, label-free, early point-of-care diagnosis and field analysis, drug detection, and environmental monitoring.
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
Corrigendum: Building an iron chromophore incorporating prussian blue analogue for photoelectrochemical water oxidation
(Wiley-VCH Verlag GmbH & Co. KGaA, 2021-09-20) Ghobadi, T. Gamze Ulusoy; Ghobadi, Amir; Demirtaş, Merve; Büyüktemiz, M.; Kübra N., Özvural; Yıldız, E. A.; Erdem, E.; Yağlıgül, H. G.; Durgun, Engin; Dede, Y.; Özbay, Ekmel; Karadaş, Ferdi
The replacement of traditional ruthenium-based photosensitizers with low-cost and abundant iron analogs is a key step for the advancement of scalable and sustainable dye-sensitized water splitting cells. In this proof-of-concept study, a pyridinium ligand coordinated pentacyanoferrate(II) chromophore is used to construct a cyanide-based CoFe extended bulk framework, in which the iron photosensitizer units are connected to cobalt water oxidation catalytic sites through cyanide linkers. The iron-sensitized photoanode exhibits exceptional stability for at least 5 h at pH 7 and features its photosensitizing ability with an incident photon-to-current conversion capacity up to 500 nm with nanosecond scale excited state lifetime. Ultrafast transient absorption and computational studies reveal that iron and cobalt sites mutually support each other for charge separation via short bridging cyanide groups and for injection to the semiconductor in our proof-of-concept photoelectrochemical device. The reorganization of the excited states due to the mixing of electronic states of metal-based orbitals subsequently tailor the electron transfer cascade during the photoelectrochemical process. This breakthrough in chromophore-catalyst assemblies will spark interest in dye-sensitization with robust bulk systems for photoconversion applications.
Open Access
Deep subwavelength light confinement in disordered bismuth nanorods as a linearly thermal‐tunable metamaterial
(Wiley-VCH Verlag, 2020) Soydan, Mahmut Can; Ghobadi, Amir; Yıldırım, Deniz Umut; Ertürk, Vakur Behçet; Özbay, Ekmel
Materials with a tunable optical response that can be controllably tailored using external stimuli excitation have undergone considerable research effort for the development of active optical devices, such as thermo‐optical modulators. Although bismuth (Bi) nanodots, embedded into glass matrices, have been proven to have a thermo‐optical response, the recyclability of the structure in solid–liquid phase transitions is a major challenge. Herein, a facile and lithography‐free fabrication method is proposed to realize densely packed stand‐alone Bi nanorods (NRs), with deep subwavelength gaps and a resonance at the midinfrared range (λ ≅ 4.462 μm). Owing to these ultrasmall gaps that support lossy Mie‐like resonances, strong field confinement is achieved, and the resonance wavelength exhibits great sensitivity to temperature, as the thermal sensitivity reaches as high as 1.0316 nm °C−1. This operation is conducted in the moderate temperature interval of 25–85 °C, which is far from the melting point of Bi. Overall, our simple, robust, and high‐performance device is highly promising for realizing optical switches, thermo‐optic modulators, and infrared camouflage.
Open Access
Diode like high-contrast asymmetric transmission of linearly polarized waves based on plasmon-tunneling effect coupling to electromagnetic radiation modes
(Institute of Physics Publishing Ltd., 2021-06-25) Khalichi, Bahram; Ghobadi, Amir; Osgouei, Ataollah Kalantari; Özbay, Ekmel
We present a narrow-band optical diode with a high-contrast forward-to-backward ratio at the near-infrared region. The design has a forward transmission of approximately $88\% $, and a backward one of less than $3\% $, yielding a contrast ratio of greater than $14.5\,$ dB at a wavelength of $1550\,$ nm. The structure is composed of a one-dimensional diffraction grating on top of a dielectric slab waveguide, both of which are made of silicon nitride (Si3N4), and all together are placed over a silver (Ag) thin film embedded on a dielectric substrate. Utilizing a dielectric-based diffraction grating waveguide on a thin silver layer leads to the simultaneous excitation of two surface plasmon modes known as long- and short-range surface plasmon polaritons (SPPs) at both interfaces of the metallic layer. The plasmon-tunneling effect, which is the result of the coupling of SPPs excited at the upper interface of the metallic layer to the radiation modes, provides a high asymmetric transmission (AT) property. The spectral response of the proposed high-contrast AT device is verified using both rigorous coupled-wave analysis as an analytical approach and finite difference time domain as a numerical one.
Open Access
Disordered and densely packed ITO nanorods as an excellent lithography-free optical solar reflector metasurface
(American Chemical Society, 2019) Yıldırım, Deniz Umut; Ghobadi, Amir; Soydan, Mahmut Can; Ateşal, Okan; Toprak, Ahmet; Çalışkan, Mehmet Deniz; Özbay, Ekmel
Precise control and stabilization of the operating temperature environment of spacecraft and satellites during their life cycle is of paramount importance to increase device reliabilities and reduce the thermomechanical constraints. Optical solar reflectors are the physical interface between the spacecraft and space, and they are broadband mirrors for the solar spectrum, while having strong thermal emission in the mid-infrared part of the electromagnetic spectrum. Strong light–matter interactions in metamaterials and metasurfaces offer significant advantages compared to the conventional methods in performance, weight, launch, and assembly costs. However, the fabrication complexity of these metastructures due to necessitating lithography hinders their upscaling, reproducibility, large-area compatibility, and mass production. In this regard, we propose a facile, lithography-free fabrication route, exploiting oblique deposition to design a metasurface based on disordered and densely packed Indium Tin Oxide (ITO) nanorod forests. The excellent light trapping capability of the nanorod forests, randomness in the geometrical dimensions of these nanorods, combined with the lossy plasmonic nature of ITO in the thermal-infrared range led to strong coupling of thermal radiation to broad plasmonic resonances and, consequently, an experimental emissivity of 0.968, in a very wide range from 2.5 to 25 μm. In the solar spectrum, the low-loss dielectric characteristic of ITO resulted in an experimental solar absorptivity as small as 0.168. Our proposed design with high throughput, robustness, low cost, and high performance, therefore, shows great promise not only for space missions, but also for promoting environmentally friendly passive radiative cooling for our planet and thermal imaging in the field of security labeling.
Open Access
Disordered and densely packed ITO nanorods as an excellent lithography-free optical solar reflector metasurface for the radiative cooling of spacecraft
(SPIE, 2019) Yıldırım, Deniz Umut; Ghobadi, Amir; Soydan, Mahmut Can; Ateşal, Okan; Toprak, Ahmet; Çalışkan, Mehmet Deniz; Özbay, Ekmel
Optical Solar Reflectors (OSRs) form the physical interface between the spacecraft and space and they are essential for the stabilization and uniform distribution of temperature throughout the spacecraft. OSRs need to possess a spectrally selective response of broadband and perfect electromagnetic wave absorption in the thermal-infrared spectral range, while strongly reflecting the solar energy input. In this work, we experimentally show that disordered and densely packed ITO nanorod forests can be used as an excellent top-layer metasurface in a metal-insulator-oxide cavity configuration, and a thermal-emissivity of 0.97 is experimentally realized in the spectral range from 2.5 to 25 μm. The low-loss dielectric response of ITO in the solar spectrum, from 300 nm to 2.5 μm range limited the solar absorptivity to an experimental value of 0.167. These make our proposed design highly promising for its application in space missions due to combining high throughput, robustness, low cost with ultra-high performance.
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
Emerging photoluminescence from defective vanadium diselenide nanosheets
(OSA - The Optical Society, 2018) Ghobadi, Amir; Ulusoy-Ghobadi, Türkan Gamze; Okyay, Ali Kemal; Özbay, Ekmel
In this paper, for the first time to our knowledge in the literature, we demonstrate photoluminescence from two-dimensional (2D) vanadium diselenide (VSe2) nanosheets (NSs). The preparation of these nanostructures is carried out with a combinational method based on nanosecond pulsed laser ablation (PLA) and chemical exfoliation. For this aim, VSe2 bulk is first ablated into nanoparticles (NPs) inside a water solution. Afterward, NPs are chemically exfoliated into NSs using lithium intercalation via ultrasonic treatment. Although VSe2 is a semimetal in its bulk form, its nanostructures show photo-responsive behavior, and it turns into a strongly luminescent material when it is separated into NSs. Based on the obtained results, the surface defects induced during the PLA process are the origin of this photoluminescence from NSs. Our findings illustrate that this new material can be a promising semiconductor for photovoltaic and light emitting diode applications.
Open Access
Fano resonance in a dolomite phase-change multilayer design for dynamically tunable omnidirectional monochromatic thermal emission
(Optica, 2022) Rahimian Omam, Zahra; Ghobadi, Amir; Khalichi, Bahram; Özbay, Ekmel
In this Letter, we unveil the unprecedented optical phonon response of CaMg(CO3)2 (dolomite) thin film in the design of a planar ultra-narrowband mid-infrared (MIR) thermal emitter. Dolomite (DLM) is a carbonate mineral composed of calcium magnesium carbonate, which can inherently accommodate highly dispersive optical phonon modes. Utilizing strong interference in the Al-DLM bilayer, a lithography-free planar thermal emitter is realized with near-unity omnidirectional emission at a specific resonance wavelength of 7.12 µm. Further incorporation of embedded vanadium dioxide (VO2) phase change material (PCM) enables the excitation of hybrid Fano resonances with dynamic spectral tunability. The findings of this study can have multiple applications, ranging from biosensing and gas sensing to thermal emission.
Open Access
Generation of additive colors with near unity amplitude using a multilayer tandem Fabry–Perot cavity
(Optica, 2021-07) Ghobadi, Amir; Rashed, Alireza Rahimi; Çağlayan, Hümeyra; Özbay, Ekmel; Köşger, Ali Cahit
In this paper, the generation of additive red-green-blue (RGB) colors in reflectance mode with near unity amplitude is demonstrated. For this purpose, a multilayer structure made of metal–insulator–metal–semiconductor–insulator stacks is designed to achieve >0.9 reflection peaks with full-width-at-half-maximum values <0.3λpeak. The pro posed design also shows near zero reflection in off-resonance spectral ranges, and this, in turn, leads to high color purity. The optimized designs are fabricated, and simulation and theoretical results are verified with characterization find ings. This work demonstrates the potential of multilayer tandem cavity designs in the realization of lithography-free large-scale compatible functional optical coatings.