Scopus İndeksli Yayınlar Koleksiyonu / Scopus Indexed Publications Collection
Permanent URI for this collectionhttps://hdl.handle.net/11147/7148
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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: 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: 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: 370Citation - Scopus: 398Graphene-Based Adaptive Thermal Camouflage(American Chemical Society, 2018) Salihoğlu, Ömer; Uzlu, Hasan Burkay; Yakar, Ozan; Aas, Shahnaz; Balcı, Osman; Kakenov, Nurbek; Balcı, Sinan; Olçum, Selim; Süzer, Şefik; Kocabaş, CoşkunIn nature, adaptive coloration has been effectively utilized for concealment and signaling. Various biological mechanisms have evolved to tune the reflectivity for visible and ultraviolet light. These examples inspire many artificial systems for mimicking adaptive coloration to match the visual appearance to their surroundings. Thermal camouflage, however, has been an outstanding challenge which requires an ability to control the emitted thermal radiation from the surface. Here we report a new class of active thermal surfaces capable of efficient real-time electrical-control of thermal emission over the full infrared (IR) spectrum without changing the temperature of the surface. Our approach relies on electro-modulation of IR absorptivity and emissivity of multilayer graphene via reversible intercalation of nonvolatile ionic liquids. The demonstrated devices are light (30 g/m2), thin (<50 μm), and ultraflexible, which can conformably coat their environment. In addition, by combining active thermal surfaces with a feedback mechanism, we demonstrate realization of an adaptive thermal camouflage system which can reconfigure its thermal appearance and blend itself with the varying thermal background in a few seconds. Furthermore, we show that these devices can disguise hot objects as cold and cold ones as hot in a thermal imaging system. We anticipate that, the electrical control of thermal radiation would impact on a variety of new technologies ranging from adaptive IR optics to heat management for outer space applications.