14 results on '"Deniz Umut Yildirim"'
Search Results
2. Nanosensors Based on Localized Surface Plasmon Resonance
- Author
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Deniz Umut Yildirim, Ekmel Ozbay, and Amir Ghobadi
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Materials science ,Nanosensor ,Nanotechnology ,Surface plasmon resonance ,Plasmon - Published
- 2021
3. All Ceramic-Based Metal-Free Ultra-broadband Perfect Absorber
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Mahmut Can Soydan, Vakur B. Erturk, Deniz Umut Yildirim, Amir Ghobadi, Ekmel Ozbay, Soydan, Mahmut Can, Ghobadi, Amir, Yıldırım, Deniz Umut, Ertürk, Vakur Behçet, and Özbay, Ekmel
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Permittivity ,Materials science ,Transition metal carbides ,Transition metal nitrides ,Biophysics ,02 engineering and technology ,Nitride ,01 natural sciences ,Biochemistry ,Carbide ,010309 optics ,Photovoltaics ,0103 physical sciences ,Metal-free ,Ceramic ,Absorption (electromagnetic radiation) ,Plasmon ,business.industry ,Metamaterial ,021001 nanoscience & nanotechnology ,Metamaterials ,Broadband perfect absorber ,visual_art ,visual_art.visual_art_medium ,Optoelectronics ,0210 nano-technology ,business ,Biotechnology - Abstract
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. TÜBİTAK
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- 2019
4. Strong light emission from a defective hexagonal boron nitride monolayer coupled to near-touching random plasmonic nanounits
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Deniz Umut Yildirim, Mahmut Can Soydan, Neval A. Cinel, Zeinab Eftekhari, Ekmel Ozbay, Amir Ghobadi, Eftekhari, Zeinab, Ghobadi, Amir, Soydan, Mahmut Can, Yıldırım, Deniz Umut, Cinel, Neval Ayşegül, and Özbay, Ekmel
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Materials science ,Photoluminescence ,business.industry ,Orders of magnitude (temperature) ,Physics::Optics ,02 engineering and technology ,Purcell effect ,021001 nanoscience & nanotechnology ,01 natural sciences ,Atomic and Molecular Physics, and Optics ,010309 optics ,Optics ,0103 physical sciences ,Monolayer ,Physics::Atomic and Molecular Clusters ,Optoelectronics ,Light emission ,Spontaneous emission ,0210 nano-technology ,business ,Luminescence ,Plasmon - Abstract
In this Letter, we demonstrate strong light emission from defective hexagonal boron nitride (hBN) defect centers upon their coupling with disorder near-touching plasmonic units. Based on numerical simulations and characterization results, the plasmonic design at thin layer thicknesses of 20 nm can provide above 2 orders of magnitude enhancement in photoluminescence (PL) spectra. Moreover, this plasmonic platform shortens the luminescence lifetime of the emitters. The proposed design can be easily extended to other plasmonic-emitter combinations where strong light-matter interaction can be achieved using large-scale compatible routes. (C) 2021 Optical Society of America
- Published
- 2021
5. Numerical analysis of a thermally tunable spectrally selective absorber enabled by an all-dielectric metamirror
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Deniz Umut Yildirim, Volkan Erturk, Ekmel Ozbay, Veysel Erçağlar, Amir Ghobadi, Erçağlar, Veysel, Ertürk, Volkan, Ghobadi, Amir, Yıldırım, Deniz Umut, and Özbay, Ekmel
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Materials science ,Silicon ,Guided-mode resonance ,business.industry ,Physics::Optics ,chemistry.chemical_element ,Germanium ,02 engineering and technology ,Dielectric ,021001 nanoscience & nanotechnology ,01 natural sciences ,Atomic and Molecular Physics, and Optics ,Selective surface ,010309 optics ,Wavelength ,Optics ,Semiconductor ,chemistry ,0103 physical sciences ,0210 nano-technology ,business ,Refractive index - Abstract
In this Letter, we numerically propose a temperature-tunable, ultra-narrowband one-way perfect near-infrared radiation absorber with high transmission in the longer wavelength neighboring spectral range. We obtained this functionality by using a guided-mode resonance-based grating-waveguide metamirror that is comprised of silicon, a spacer dielectric, an absorbing semiconductor, and germanium. Within the ultra-narrow bandwidth of the guided-mode resonance excited at 1.16 µm with a full width at half-maximum of 3.3 nm, we confirmed perfect absorption when light is incident from one of the two opposite directions. Excitation from the opposite direction resulted in perfect reflection. The thickness of the entire structure is limited to about one third the operating wavelength. Furthermore, due to the temperature tunability of silicon and germanium the thermo-optical sensitivity was found to be approximately 0.068 nm/K. In addition to this spectral tunability, our proposed device supports transparency windows with 80% transmission in the higher wavelength ranges. Our device is highly promising in the applications of thermo-tunable modulators and obtaining single frequency near-infrared signals from broadband sources.
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- 2020
6. One-way and near-absolute polarization insensitive near-perfect absorption by using an all-dielectric metasurface
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Andriy E. Serebryannikov, Deniz Umut Yildirim, Amir Ghobadi, Mahmut Can Soydan, Ekmel Ozbay, Yıldırım, Deniz Umut, Ghobadi, Amir, Soydan, Mahmut Can, Serebryannikov, Andriy E., and Özbay, Ekmel
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Materials science ,Guided-mode resonance ,business.industry ,Resonance ,Physics::Optics ,02 engineering and technology ,Dielectric ,Grating ,021001 nanoscience & nanotechnology ,Polarization (waves) ,01 natural sciences ,Ray ,Atomic and Molecular Physics, and Optics ,010309 optics ,Laser linewidth ,Wavelength ,Optics ,0103 physical sciences ,0210 nano-technology ,business - Abstract
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 mu m (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. (C) 2020 Optical Society of America
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- 2020
7. Lithography-Free Random Bismuth Nanostructures For Full Solar Spectrum Harvesting And Mid-Infrared Sensing
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Mahmut Can Soydan, Deniz Umut Yildirim, Alpan Bek, Ekmel Ozbay, Amir Ghobadi, Vakur B. Erturk, ElifSarıgül Duman, Soydan, Mahmut Can, Ghobadi, Amir, Yıldırım, Deniz Umut, Ertürk, Vakur Behçet, and Özbay, Ekmel
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Nanostructure ,Materials science ,business.industry ,Solar spectra ,Mid infrared ,chemistry.chemical_element ,Ultrahigh sensitivity ,Atomic and Molecular Physics, and Optics ,Lithography‐free fabrication ,Electronic, Optical and Magnetic Materials ,Bismuth ,Broadband absorbers ,chemistry ,Narrowband absorbers ,Optoelectronics ,business ,Lithography - Abstract
A lithography‐free, double‐functional single bismuth (Bi) metal nanostructure is designed, fabricated, and characterized for ultrabroadband absorption in the visible (vis) and near‐infrared (NIR) ranges, and for a narrowband response with ultrahigh refractive index sensitivity in the mid‐infrared (MIR) range. To achieve a large‐scale fabrication of the design in a lithography‐free route, the oblique‐angle deposition approach is used to obtain densely packed and randomly spaced/oriented Bi nanostructures. It is shown that this fabrication technique can provide a bottom‐up approach to controlling the length and spacing of the design. The characterization findings reveal a broadband absorbance above 0.8 in vis and NIR, and a narrowband absorbance centered around 6.54 µm. Dense architecture and extraordinary permittivity of Bi provide strong field confinement in ultrasmall gaps between nanostructures, and this can be utilized for a sensing application. An ultrahigh sensitivity of 2151 nm refractive‐index unit (RIU–1) is acquired, which is, as far as it is known, the experimentally highest sensitivity attained so far. The simple and large‐scale compatible fabrication route of the design together with the extraordinary optical response of Bi coating makes this design promising for many optoelectronic and sensing applications. Scientific and Technological Research Council of Turkey DPT‐HAMIT. Grant Numbers: 113E331, 114E374, 115F560 Turkish Academy of Sciences Türkiye Bilimsel ve Teknolojik Araştirma Kurumu. Grant Number: 115F560
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- 2020
8. Disordered and densely packed ITO nanorods as an excellent lithography-free optical solar reflector metasurface for the radiative cooling of spacecraft
- Author
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Deniz Umut Yildirim, Okan Atesal, Mehmet Deniz Çalişkan, Amir Ghobadi, Ahmet Toprak, Mahmut Can Soydan, Ekmel Ozbay, Yıldırım, Deniz Umut, Ghobadi, Amir, Soydan, Mahmut Can, Ateşal, Okan, Toprak, Ahmet, Çalışkan, Mehmet Deniz, and Özbay, Ekmel
- Subjects
Transparent conductive oxides ,Materials science ,Spacecraft ,Radiative cooling ,business.industry ,Oblique-angle deposition ,Solar energy ,Space exploration ,Metasurfaces ,Optical solar re ectors ,Broadband ,Plasmonics ,Optoelectronics ,Nanorod ,Astrophysics::Earth and Planetary Astrophysics ,business ,Lithography ,Plasmon - Abstract
Date of Conference: 11-15 August 2019 Conference Name: SPIE Nanoscience + Engineering, 2019 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. The Society of Photo-Optical Instrumentation Engineers (SPIE)
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- 2019
9. Disordered and densely packed ITO nanorods as an excellent lithography-free optical solar reflector metasurface
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Mahmut Can Soydan, Amir Ghobadi, Ekmel Ozbay, Deniz Umut Yildirim, Ahmet Toprak, Mehmet Deniz Çalişkan, Okan Atesal, Yıldırım, Deniz Umut, Ghobadi, Amir, Soydan, Mahmut Can, Ateşal, Okan, Toprak, Ahmet, Çalışkan, Mehmet Deniz, and Özbay, Ekmel
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Fabrication ,Materials science ,Transparent conductive oxides ,Oblique-angle deposition ,Physics::Optics ,02 engineering and technology ,7. Clean energy ,01 natural sciences ,010309 optics ,Operating temperature ,0103 physical sciences ,Metamaterial perfect absorbers ,Electrical and Electronic Engineering ,Lithography ,Plasmon ,Spacecraft ,business.industry ,Metamaterial ,021001 nanoscience & nanotechnology ,Atomic and Molecular Physics, and Optics ,Electronic, Optical and Magnetic Materials ,Indium tin oxide ,Metasurfaces ,13. Climate action ,Physics::Space Physics ,Optical solar reflectors ,Optoelectronics ,Plasmonics ,Nanorod ,0210 nano-technology ,business ,Biotechnology - Abstract
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 pm. 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.
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- 2019
10. Colorimetric and near-absolute polarization-insensitive refractive-index sensing in all-dielectric guided-mode resonance based metasurface
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Murat Gokbayrak, Amir Ghobadi, Bayram Butun, Ahmet Toprak, Deniz Umut Yildirim, Ekmel Ozbay, Mahmut Can Soydan, Yıldırım, Deniz Umut, Ghobadi, Amir, Soydan, Mahmut Can, Gökbayrak, Murat, Toprak, Ahmet, Bütün, Bayram, and Özbay, Ekmel
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Materials science ,Resonance structures ,Guided-mode resonance ,business.industry ,02 engineering and technology ,Dielectric ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Polarization (waves) ,01 natural sciences ,Quantum mechanics ,0104 chemical sciences ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,General Energy ,Optics ,Polarization ,Molecule ,Physical and Theoretical Chemistry ,0210 nano-technology ,business ,Thickness ,Layers ,Refractive index - Abstract
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.
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- 2019
11. Publisher Correction: Near-absolute polarization insensitivity in graphene based ultra-narrowband perfect visible light absorber
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Deniz Umut Yildirim, Amir Ghobadi, and Ekmel Ozbay
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Multidisciplinary ,Materials science ,business.industry ,Graphene ,lcsh:R ,lcsh:Medicine ,02 engineering and technology ,021001 nanoscience & nanotechnology ,Polarization (waves) ,Publisher Correction ,01 natural sciences ,law.invention ,010309 optics ,Optics ,Narrowband ,law ,0103 physical sciences ,ComputingMethodologies_DOCUMENTANDTEXTPROCESSING ,lcsh:Q ,lcsh:Science ,0210 nano-technology ,business ,Visible spectrum - Abstract
A correction to this article has been published and is linked from the HTML and PDF versions of this paper. The error has been fixed in the paper.
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- 2018
12. Deep Subwavelength Light Confinement in Disordered Bismuth Nanorods as a Linearly Thermal‐Tunable Metamaterial
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Mahmut Can Soydan, Amir Ghobadi, Vakur B. Erturk, Ekmel Ozbay, Deniz Umut Yildirim, Soydan, Mahmut Can, Ghobadi, Amir, Deniz Umut, Deniz Umut, Ertürk, Vakur Behçet, and Özbay, Ekmel
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Lithography-free ,Materials science ,Thermally-tunable ,business.industry ,Metamaterial ,Tunable metamaterials ,chemistry.chemical_element ,Condensed Matter Physics ,Bismuth ,chemistry ,Metamaterials ,Thermal ,Optoelectronics ,General Materials Science ,Nanorod ,business - Abstract
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 (lambda approximately equal to 4.462 mu m). 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 degrees C-1. This operation is conducted in the moderate temperature interval of 25-85 degrees 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.
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- 2020
13. Near-absolute polarization insensitivity in grapheme based ultra-narrowband perfect visible light absorber
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Ekmel Ozbay, Deniz Umut Yildirim, Amir Ghobadi, and Özbay, Ekmel
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Materials science ,Terahertz radiation ,Nanophotonics ,lcsh:Medicine ,Physics::Optics ,02 engineering and technology ,Dielectric ,Grating ,01 natural sciences ,Article ,law.invention ,010309 optics ,Narrowband ,law ,0103 physical sciences ,lcsh:Science ,Absorption (electromagnetic radiation) ,Multidisciplinary ,business.industry ,Graphene ,lcsh:R ,021001 nanoscience & nanotechnology ,Optoelectronics ,lcsh:Q ,0210 nano-technology ,business ,Visible spectrum - Abstract
Strong light-graphene interaction is essential for the integration of graphene to nanophotonic and optoelectronic devices. The plasmonic response of graphene in terahertz and mid-infrared regions enhances this interaction, and other resonance mechanisms can be adopted in near-infrared and visible ranges to achieve perfect light absorption. However, obtaining near-absolute polarization insensitivity with ultra-narrow absorption bandwidth in the visible and near-infrared regimes remains a challenge. In this regard, we numerically propose a graphene perfect absorber, utilizing the excitation of guided-modes of a dielectric slab waveguide by a novel sub-wavelength dielectric grating structure. When the guided-mode resonance is critically coupled to the graphene, we obtain perfect absorption with an ultra-narrow bandwidth (full-width at half-maximum) of 0.8 nm. The proposed design not only preserves the spectral position of the resonance, but also maintains >98% absorption at all polarization angles. The spectral position of the resonance can be tuned as much as 400 nm in visible and near-infrared regimes by tailoring geometrical parameters. The proposed device has great potential in efficient, tunable, ultra-sensitive, compact and easy-to-fabricate advanced photodetectors and color filters.
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- 2018
14. Unveiling the optical parameters of vanadium dioxide in the phase transition region: a hybrid modeling approach
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Yilmaz Durna, Hodjat Hajian, Necdet Sağlam, Koray Aydin, Amir Ghobadi, Deniz Umut Yildirim, Ekmel Ozbay, Hamza Kurt, Mehmet Cihan Çakir, Hasan Kocer, Çakır, Mehmet Cihan, Koçer, Hasan, Yıldırım, Deniz Umut, Ghobadi, Amir, Hajian, Hodjat, Özbay, Ekmel, TOBB ETU, Faculty of Engineering, Department of Electrical & Electronics Engineering, TOBB ETÜ, Mühendislik Fakültesi, Elektrik ve Elektronik Mühendisliği Bölümü, and Kurt, Hamza
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Phase transition ,Metal-Insulator Transition ,Materials science ,General Chemical Engineering ,Transfer-matrix method (optics) ,02 engineering and technology ,01 natural sciences ,Thermochromatic Materials ,Metal ,0103 physical sciences ,Metal–insulator transition ,010302 applied physics ,Range (particle radiation) ,business.industry ,Metamaterial ,General Chemistry ,021001 nanoscience & nanotechnology ,Vanadium Dioxide ,Wavelength ,visual_art ,visual_art.visual_art_medium ,Optoelectronics ,Condensed Matter::Strongly Correlated Electrons ,Photonics ,0210 nano-technology ,business - Abstract
The phase change behavior of vanadium dioxide (VO2) has been widely explored in a variety of optical and photonic applications. Commonly, its optical parameters have been studied in two extreme regimes: hot (metallic) and cold (insulating) states. However, in the transition temperatures, VO(2)acts like an inherent metamaterial with mixed metallic-insulating character. In this range, the portions of metallic and insulating inclusions are tuned by temperature, and therefore a gradual change of optical parameters can be achieved. In this paper, a universal hybrid modeling approach is developed to model VO(2)in the intermediate region. For this aim, the measured reflectivity data, is analyzed and matched through the transfer matrix method (TMM) simulations where an effective medium theory (EMT) is employed. Based on the findings of this approach, not only the relative portions of inclusions are tailored but also their grain shapes are significantly altered in the transition range. Finally, the modeling approach is testified by experimental findings through dynamic device applications operating at short and mid infrared wavelengths. In addition, the hysteretic behaviors on electrical, optical, and structural parameters of the VO(2)film along the heating and cooling cycles are demonstrated by the experiments and scrutinized by the simulations.
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