Researcher:
Ramazanoğlu, Serap Aksu

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Serap Aksu

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Ramazanoğlu

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Ramazanoğlu, Serap Aksu

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2019 - 201912020 - 20225

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Researcher Of Publications: search.filters.isAuthorOfPublication.270c0f31-4cd7-40cb-878a-f004cc8fe023

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    Investigating monolayer protein-protein binding using surface enhanced IR spectroscopy
    (IEEE, 2019) Korkmaz, Semih; Department of Physics; Ramazanoğlu, Serap Aksu; Faculty Member; Department of Physics; College of Sciences; 243745
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    Experimental study of a quad-band metamaterial-based plasmonic perfect absorber as a biosensor
    (Mdpi, 2022) Korkmaz, Semih; Turkmen, Mustafa; N/A; Department of Physics; N/A; Öktem, Evren; Ramazanoğlu, Serap Aksu; Yazdaanpanah, Ramin; Master Student; Faculty Member; PhD Student; Department of Physics; Graduate School of Sciences and Engineering; College of Sciences; Graduate School of Sciences and Engineering; N/A; 243745; N/A
    We present a metamaterial-based perfect absorber (PA) that strongly supports four resonances covering a wide spectral range from 1.8 mu m to 10 mu m of the electromagnetic spectrum. The designed perfect absorber has metal-dielectric-metal layers where a MgF2 spacer is sandwiched between an optically thick gold film and patterned gold nanoantennas. The spectral tuning of PA is achieved by calibrating the geometrical parameters numerically and experimentally. The manufactured quad-band plasmonic PA absorbs light close to the unity. Moreover, the biosensing capacity of the PA is tested using a 14 kDa S100A9 antibody, which is a clinically relevant biomarker for brain metastatic cancer cells. We utilize a UV-based photochemical immobilization technique for patterning of the antibody monolayer on a gold surface. Our results reveal that the presented PA is eligible for ultrasensitive detection of such small biomarkers in a point-of-care device to potentially personalize radiotherapy for patients with brain metastases.
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    PublicationOpen Access
    A hybrid broadband metalens operating at ultraviolet frequencies
    (Nature Publishing Group (NPG), 2021) Department of Physics; Ali, Farhan; Ramazanoğlu, Serap Aksu; Faculty Member; Department of Physics; Graduate School of Sciences and Engineering; College of Sciences; N/A; 243745
    The investigation on metalenses have been rapidly developing, aiming to bring compact optical devices with superior properties to the market. Realizing miniature optics at the UV frequency range in particular has been challenging as the available transparent materials have limited range of dielectric constants. In this work we introduce a low absorption loss and low refractive index dielectric material magnesium oxide, MgO, as an ideal candidate for metalenses operating at UV frequencies. We theoretically investigate metalens designs capable of efficient focusing over a broad UV frequency range (200–400 nm). The presented metalenses are composed of sub-wavelength MgO nanoblocks, and characterized according to the geometric Pancharatnam–Berry phase method using FDTD method. The presented broadband metalenses can focus the incident UV light on tight focal spots (182 nm) with high numerical aperture (NA ≈ 0.8). The polarization conversion efficiency of the metalens unit cell and focusing efficiency of the total metalens are calculated to be as high as 94%, the best value reported in UV range so far. In addition, the metalens unit cell can be hybridized to enable lensing at multiple polarization states. The presented highly efficient MgO metalenses can play a vital role in the development of UV nanophotonic systems and could pave the way towards the world of miniaturization.
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    PublicationOpen Access
    A narrow-band multi-resonant metamaterial in near-ir
    (Multidisciplinary Digital Publishing Institute (MDPI), 2020) Ali, Farhan; Department of Physics; Ramazanoğlu, Serap Aksu; Faculty Member; Department of Physics; College of Sciences; 243745
    We theoretically investigate a multi-resonant plasmonic metamaterial perfect absorber operating between 600 and 950 nm wavelengths. The presented device generates 100% absorption at two resonance wavelengths and delivers an ultra-narrow band (sub-20 nm) and high quality factor (Q = 44) resonance. The studied perfect absorber is a metal–insulator–metal configuration where a thin MgF2 spacer is sandwiched between an optically thick gold layer and uniformly patterned gold circular nanodisc antennas. The localized and propagating nature of the plasmonic resonances are characterized and confirmed theoretically. The origin of the perfect absorption is investigated using the impedance matching and critical coupling phenomenon. We calculate the effective impedance of the perfect absorber and confirm the matching with the free space impedance. We also investigate the scattering properties of the top antenna layer and confirm the minimized reflection at resonance wavelengths by calculating the absorption and scattering cross sections. The excitation of plasmonic resonances boost the near-field intensity by three orders of magnitude which enhances the interaction between the metamaterial surface and the incident energy. The refractive index sensitivity of the perfect absorber could go as high as S = 500 nm/RIU. The presented optical characteristics make the proposed narrow-band multi-resonant perfect absorber a favorable platform for biosensing and contrast agent based bioimaging.
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    PublicationOpen Access
    Surface enhanced vibrational spectroscopy using ultra narrow-band perfect absorber
    (Society of Photo-optical Instrumentation Engineers (SPIE), 2020) Department of Physics; Ramazanoğlu, Serap Aksu; Faculty Member; Department of Physics; College of Sciences; 243745
    In this work, we present a narrow-band (sub-100 cm-1) and multi-band metamaterial perfect absorber operating in the mid-IR frequency regime for analysis of biomolecules with vibrational spectroscopy. The presented perfect absorber is based on multi-layer metamaterial plasmonic nanoantennas. We used numerical and experimental work to fine tune the parameters of the PA and control its spectral response. The suggested PA system provides high absorbance values (100%) in the mid-IR region and near-field enhancement factor of 103 at the corresponding resonance values. The experimental results are well agreeing the numerical results. The working principle of the presented perfect absorption can be both explained by impedance matching and critical coupling phenomenon. The fabricated PA shows strong narrow band resonance and all the resonance energy could be transferred to thin films (10 nm) for higher sensitivity. In addition, PA shows multi-band resonances within the mid-IR region, thus it can be effectively used for simultaneously detecting the different biomolecular fingerprints. In this sense, we experimentally observed absorption of carbonyl (C=O) and asymmetric methyl (-CH3) stretching bands of thin polymethyl methacrylate (PMMA) film on the narrow band resonance of PA.
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    PublicationOpen Access
    Mid-infrared narrow band plasmonic perfect absorber for vibrational spectroscopy
    (Elsevier, 2020) Korkmaz, Semih; Türkmen, Mustafa; Department of Physics; Ramazanoğlu, Serap Aksu; Faculty Member; Department of Physics; College of Sciences; 243745
    The introduction of narrow band perfect absorbers (PAs) operating in mid-infrared (IR) frequencies has the potential to improve the study of biomolecule monolayers using surface enhanced vibrational spectroscopy. However, wavelength dependent radiation and nonradiative losses are limiting factors to obtain narrow band absorption resonance, having full width at half maximum (FWHM) below 150 cm(-1) in the mid-IR frequency range. In this work, we numerically and experimentally present an engineered narrow band PA with FWHM of 85 cm(-1) operating in mid-IR frequencies. The PA is based on multi-layer metamaterial plasmonic nanoantennas. We used numerical and experimental work to fine tune the parameters of the PA in order to control its spectral response. The suggested PA system strongly provides high absorption values (100 %) in the mid-IR region and near-field enhancement factor of 10(3) at the corresponding resonance values. The fabricated PA shows strong narrow band resonance and all the resonance energy could be transferred to thin films (10 nm) for higher sensitivity. In addition, PA shows multi-band resonances within the mid-IR region, thus it can be effectively used for simultaneously detecting the different biomolecular fingerprints. In this sense, we experimentally observed absorption of carbonyl nu(C=O) and asymmetric methyl nu(-CH3) stretching bands of thin polymethyl methacrylate (PMMA) film on the narrow band resonances of PA. The suggested system has potential to be used in live cell-membrane investigations, as multi-band structure enables investigation of both lipids and proteins.