Polat, Nahit
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Polat, N
Polat, N.
Polat, N.
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04.04. Department of Photonics
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137
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143
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| Journal | Count |
|---|---|
| ACS Applied Nano Materials | 2 |
| ACS Photonics | 2 |
| Applied Physics Letters | 2 |
| ChemistrySelect | 1 |
| Journal of Materials Chemistry C | 1 |
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Doctoral Thesis Strong and Weak Light-Matter Interactions in Plasmonic and Optical Cavities(01. Izmir Institute of Technology, 2023) Polat, Nahit; Balcı, SinanThis thesis investigates the interaction of light and matter through both experimental and theoretical approaches, focusing on two key topics: Strong and Weak coupling. We also examine the field of strong light-matter interactions under two headings: plasmonic and optical cavities. In the section on plasmonic cavities, we focus on the strong coupling between surface plasmon polaritons and excitons with different optical properties and localized surface plasmon resonance. We also discuss the strong coupling between localized surface plasmon resonance and excitons in plasmonic nanoparticles with different optical properties due to their different shapes. This thesis focuses on the theoretical and optical characterization of the aforementioned topics. Therefore, details on the manufacturing processes are not given. Instead, it presents a comparative analysis of optical measurement results and related simulation data, to which I have contributed more. In addition, we demonstrate for the first time hyperspectral imaging of exciton polaritons at optical microcavities. Two metal thin films acting as reflectors and a polymer matrix containing a collection of quantum emitters form the hybrid system for polariton imaging. We show a strong exciton-photon interaction between photons trapped in the microcavity and Frenkel excitons of dye molecules placed inside the optical microcavity. We find that exciton polaritons in the optical microcavity can be imaged and spatially mapped using hyperspectral imaging in the visible region. In the field of weak light-matter interactions, the focus of the thesis is on the Fano resonance, which is a unique case in the weak coupling regime. The degree of coupling between interacting systems plays a critical role in determining the extent to which constructive and destructive interference phenomena occur in the system. An important example of destructive interference is the Fano resonance, which is caused by interference between two optical paths that are characterized by different states: one is narrow and discrete, and the other is broad and continuum. This is the first study to theoretically investigate the destructive interference between subwavelength excitonic nanoparticles placed on the surface of a prism for Fano resonance observations and the evanescent wave scattering on the prism surface. In an attempt to understand the intricate dynamics between the evanescent wave and the Fano resonance, we study the effect of changing the angle of incidence of the incident plane wave on the properties of the Fano resonance. Furthermore, we also investigate how the size of the excitonic nanoparticles and the absorption linewidth influence the properties of the Fano resonance.Article Citation - WoS: 9Citation - Scopus: 9Fourier Transform Plasmon Resonance Spectrometer Using Nanoslit-Nanowire Pair(American Institute of Physics, 2019) Uulu, Doolos Aibek; Ashirov, Timur; Polat, Nahit; Yakar, Ozan; Balcı, Sinan; Kocabaş, CoşkunIn this paper, we present a nanoscale Fourier transform spectrometer using a plasmonic interferometer consisting of a tilt subwavelength slit-nanowire pair on a metallic surface fabricated by the focused ion beam microfabrication technique. The incident broadband light strongly couples with the surface plasmons on the gold surface, and thus, surface plasmon polaritons (SPPs) are generated. The launched SPPs interfere with the incident light and generate high contrast interference fringes in the nanoslit. The transmitted SPPs through the metal nanoslit can decouple into free space and are collected by an objective in the far field. The spectroscopic information of the incidence light is obtained by fast Fourier transform of the fringe pattern of the SPPs. In our design, there is no need for a bulky dispersive spectrometer or dispersive optical elements. The dimension of the spectrometer is around 200 mu m length. Our design is based on inherent coherence of the SPP waves propagating through the subwavelength metal nanoslit structures etched into an opaque gold film.Article Citation - WoS: 17Citation - Scopus: 19Strong Coupling of Carbon Quantum Dots in Liquid Crystals(American Chemical Society, 2022) Sarısözen, Sema; Polat, Nahit; Mert Balcı, Fadime; Güvenç, Çetin Meriç; Kocabaş, Çoşkun; Yağlıoğlu, Halime Gül; Balcı, SinanCarbon quantum dots (CDs) have recently received a tremendous amount of interest owing to their attractive optical properties. However, CDs have broad absorption and emission spectra limiting their application ranges. We herein, for the first time, show synthesis of water-soluble red emissive CDs with a very narrow line width (∼75 meV) spectral absorbance and hence demonstrate strong coupling of CDs and plasmon polaritons in liquid crystalline mesophases. The excited state dynamics of CDs has been studied by ultrafast transient absorption spectroscopy, and CDs display very stable and strong photoluminescence emission with a quantum yield of 35.4% and a lifetime of ∼2 ns. More importantly, we compare J-aggregate dyes with CDs in terms of their absorption line width, photostability, and ability to do strong coupling, and we conclude that highly fluorescent CDs have a bright future in the mixed light-matter states for emerging applications in future quantum technologies.Article Citation - WoS: 25Citation - Scopus: 25Colloidal Bimetallic Nanorings for Strong Plasmon Exciton Coupling(American Chemical Society, 2020) Güvenç, Çetin Meriç; Mert Balcı, Fadime; Sarısözen, Sema; Polat, Nahit; Balcı, SinanNobel-metal nanostructures strongly localize and manipulate light at nanoscale dimension by supporting surface plasmon polaritons. In fact, the optical properties of the nobel-metal nanostructures strongly depend on their morphology and composition. Until now, various metal nanostructures such as nanocubes, nanoprisms, nanorods, and recently hollow nanostructures have been demonstrated. In addition, the plasmonic field can be further enhanced at nanoparticle dimers and aggregates because of highly localized and intense optical fields, which is known as "plasmonic hot spots". However, colloidally synthesized and circular-shaped nanoring nanostructures with plasmonic hot spots are still lacking. We, herein, show for the first time that colloidal bimetallic nanorings with plasmonic nanocavities and tunable plasmon resonance wavelengths can be synthesized via colloidal synthesis and galvanic replacement reactions. In addition, in the strong coupling regime, plasmons in nanorings and excitons in J-aggregates interact strongly and nanoring-shaped colloidal plexcitonic nanoparticles are demonstrated. The results reveal that the optical properties of the nanoring and the onset of strong coupling can be tamed by the galvanic replacement reaction. Further, the plasmonic nanocavity in the nanorings has immense potential for applications in sensing and spectroscopy because of the space, enclosed by the plasmonic nanocavity, is empty and accessible to a variety of molecules, ions, and quantum dots.Article Citation - WoS: 2Citation - Scopus: 2Room Temperature Emission From Single Defects in Wo3 Enhanced by Plasmonic Nanocrystals(American Institute of Physics, 2021) Özçeri, Elif; Polat, Nahit; Balcı, Sinan; Tarhan, EnverRoom temperature light emission from optically active defect centers in two-dimensional layered materials has attracted great interest in recent years owing to the critical applications in the field of quantum information technologies. Therefore, efficient generation, detection, characterization, and manipulation of spatially localized emission from the defect centers are of crucial importance. Here, we report localized, stable, and bright room temperature photoluminescence (PL) emission from defects in WO3. In particular, the experimentally observed polarized and power dependent PL emission shows single photon characteristics. In addition, density functional theory calculations indicate that the source of the emission is most probably oxygen vacancy defects in WO3. The PL emission obtained from the localized defect centers in WO3 at room temperature has been, further, enhanced more than 20 times by using plasmonic gold nanoparticles.Master Thesis Temperature Dependence of Zero Phonon Line Emission From Defects in Hexagonal Boron Nitride and Design of Photon-Pair Source(Izmir Institute of Technology, 2017) Polat, Nahit; Ateş, SerkanThis thesis presents studies of the defect centers in hBN and design of nonlinear waveguide. The multilayer hBN flakes and Si3N4 waveguide are available materials in modern nanophotonics applications. The color centers in hBN are consisted of quantized states because each defect center has different saturation power and dipole polarization. The line shape of emission from defect centers is directly depended photon vibrations and temperature of sample. Moreover, phonon bands in the color centers affect the wavelength of emission and we statistically worked on the phonon effects on ZPL. The Si3N4 waveguide can be more efficient chip scale photon pair sources to create entangled photons in visible band. The zero dispersion wavelength calculations give an efficient waveguide geometry as 650×600 nm2 for 780 nm pump wavelength.Article Citation - WoS: 5Citation - Scopus: 5Light-Induced, Liquid Crystal-Templated Fabrication of Large-Area Pure Nanoporous Gold Films With High-Density Plasmonic Cavities(Amer Chemical Soc, 2024) Orhan, Ozan Baran; Polat, Nahit; Demir, Seren; Balci, Fadime Mert; Balci, SinanNanoporous gold (NPG) films are three-dimensional gold (Au) frameworks characterized by a uniform distribution of nanoscale irregular pores. Typically produced via a dealloying process, where the less noble silver (Ag) is selectively etched out, NPG films offer a large surface area, excellent chemical stability, remarkable catalytic activity, unique optical properties, and biocompatibility. These attributes make them invaluable for applications in catalysis, plasmonics, biosensors, and nanophotonics. However, the presence of residual Ag from the dealloying process can limit their performance in certain applications. In this study, we report a novel method for the fabrication of ultrapure, large-area NPG films (several cm2) using a light-induced and liquid crystal-templated method. A hexagonal lyotropic liquid crystal containing a strong acid and a nonionic surfactant is combined with an aqueous solution of HAuCl4, followed by the photochemical synthesis of gold nanoparticles (NPs) within the liquid crystal. After calcination of the Au NP-containing liquid crystal film at high temperature, pure NPG films are produced. We demonstrate surface-enhanced Raman spectroscopy (SERS) of Rhodamine 6G (R6G) molecules adsorbed on the NPG films and detect extremely low concentrations (below 10-6 M) of R6G. Additionally, we thoroughly investigated the formation and optical properties of the NPG films. The results reveal that the ultrapure NPG films contain high-density plasmonic nanocavities, where substantial electromagnetic fields are generated, leading to significant enhancement of optical processes at nanoscale dimensions.Article Citation - WoS: 13Citation - Scopus: 15Hybrid J-aggregate-graphene phototransistor(American Chemical Society, 2020) Yakar, Ozan; Balcı, Osman; Uzlu, Burkay; Polat, Nahit; Arı, Ozan; Tunç, İlknur; Balcı, SinanJ-aggregates are fantastic self-assembled chromophores with a very narrow and extremely sharp absorbance band in the visible and near-infrared spectrum, and hence they have found many exciting applications in nonlinear optics, sensing, optical devices, photography, and lasing. In silver halide photography, for example, they have enormously improved the spectral sensitivity of photographic process due to their fast and coherent energy migration ability. On the other hand, graphene, consisting of single layer of carbon atoms forming a hexagonal lattice, has a very low absorption coefficient. Inspired by the fact that J-aggregates have carried the role to sense the incident light in silver halide photography, we would like to use Jaggregates to increase spectral sensitivity of graphene in the visible spectrum. Nevertheless, it has been an outstanding challenge to place isolated J-aggregate films on graphene to extensively study interaction between them. We herein noncovalently fabricate isolated J-aggregate thin films on graphene by using a thin film fabrication technique we termed here membrane casting (MC). MC significantly simplifies thin film formation of water-soluble substances on any surface via porous polymer membrane. Therefore, we reversibly modulate the Dirac point of graphene in the J-aggregate/graphene van der Waals (vdW) heterostructure and demonstrate an all-carbon phototransistor gated by visible light. Owing to the hole transfer from excited excitonic thin film to graphene layer, graphene is hole-doped. In addition, spectral and power responses of the all-carbon phototransistor have been measured by using a tunable laser in the visible spectrum. The first integration of J-aggregates with graphene in a transistor structure enables one to reversibly write and erase charge doping in graphene with visible light that paves the way for using J-aggregate/graphene vdW heterostructures in optoelectronic applications.Article Citation - WoS: 1Citation - Scopus: 1Hyperspectral Imaging of Exciton Polaritons in Optical Microcavities(Amer Chemical Soc, 2024) Polat, Nahit; Yakar, Ozan; O''zdemir, Sahin K.; Balci, SinanPhotons can be confined in optical microcavities both spectrally and spatially, which allows us to study the light-matter interaction in both weak and strong coupling regimes. While the former is identified by the Purcell factor, which quantifies the suppression or enhancement of the spontaneous emission rate of the quantum emitters coupled to the cavity modes, the latter is identified by the formation of hybrid photon-matter modes called exciton polaritons and thus represents an avoided crossing in the spectra. Until now, various imaging and spectroscopic techniques have been extensively used to study exciton polariton formation in optical microcavities, and the coupling between excitons and photons has been statically and dynamically tuned. Herein, we demonstrate the hyperspectral imaging of exciton polaritons in optical microcavities. Two thin metal films acting as reflectors and a polymer matrix containing a collection of quantum emitters form a hybrid system for polariton imaging. We show a strong exciton-photon interaction between photons confined in the microcavity and Frenkel excitons of dye molecules placed inside the optical microcavity. We find that exciton polaritons can be imaged and spatially mapped in the optical microcavity by using hyperspectral imaging in the visible region. We envision that our findings will help us to understand exciton polariton formation in the spectral and spatial domains at the same time across different coupling regimes.Article Citation - WoS: 12Citation - Scopus: 14Laser Assisted Synthesis of Anisotropic Metal Nanocrystals and Strong Light-Matter Coupling in Decahedral Bimetallic Nanocrystals(Royal Society of Chemistry, 2021) Mert Balcı, Fadime; Sarısözen, Sema; Polat, Nahit; Güvenç, Çetin Meriç; Karadeniz, Uğur; Tertemiz, Necip Ayhan; Balcı, SinanThe advances in colloid chemistry and nanofabrication allowed us to synthesize noble monometallic and bimetallic nanocrystals with tunable optical properties in the visible and near infrared region of the electromagnetic spectrum. In the strong coupling regime, surface plasmon polaritons (SPPs) of metal nanoparticles interact with excitons of quantum dots or organic dyes and plasmon-exciton hybrid states called plexcitons are formed. Until now, various shaped metal nanoparticles such as nanorods, core-shell nanoparticles, hollow nanoparticles, nanoprisms, nanodisks, nanorings, and nanobipyramids have been synthesized to generate plasmon-exciton mixed states. However, in order to boost plasmon-exciton interaction at nanoscale dimensions and expand the application of plexcitonic nanocrystals in a variety of fields such as solar cells, light emitting diodes, and nanolasers, new plexcitonic nanocrystals with outstanding optical and chemical properties remain a key goal and challenge. Here we report laser-assisted synthesis of decahedral shaped noble metal nanocrystals, tuning optical properties of the decahedral shaped nanocrystals by galvanic replacement reactions, colloidal synthesis of bimetallic decahedral shaped plexcitonic nanocrystals, and strong plasmon-plasmon interaction in bimetallic decahedral shaped noble metal nanocrystals near a metal film. We photochemically synthesize decahedral Ag nanoparticles from spherical silver nanoparticles by using a 488 nm laser. The laser assisted synthesis of silver nanoparticles yields decahedral (bicolored) and prism (monocolored) shaped silver nanocrystals. The decahedral shaped nanoparticles were selectively separated from prism shaped nanoparticles by centrifugation. The optical properties of decahedral nanocrystals were tuned by the galvanic replacement reaction between gold ions and silver atoms. Excitons of J-aggregate dyes and SPPs of decahedral bimetallic nanoparticles strongly couple and hence decahedral shaped plexcitonic nanoparticles are prepared. In addition, localized SPPs of decahedral shaped bimetallic nanocrystals interact strongly with the propagating SPPs of a flat silver film and hence new hybrid plasmonic modes (plasmonic nanocavities) are generated. The experimental results are further fully corroborated by theoretical calculations including decahedral shaped plexcitonic nanoparticles and decahedral nanoparticles coupled to flat metal films.