Browsing by Subject "Surface plasmon"

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    Boosting the efficiency of organic solar cells via plasmonic gold nanoparticles and thiol functionalized conjugated polymer
    (Elsevier, 2022-11) Karakurt, O.; Alemdar, E.; Cevher, D.; Gulmez, S.; Taylan, Umut; Cevher, S. C.; Hizalan Ozsoy, G.; Ortac, Bulend; Cirpan, A.
    Conjugated polymers are promising low-cost, lightweight, and flexible candidates for scalable photovoltaic applications to establish decarbonized energy technologies. However, they possess deficiencies in terms of their lower charge mobility and exciton diffusion length compared to their inorganic counterparts, impeding the efficient charge extraction at high active layer thickness values. In this manner, active layer composition should be tuned to improve light harvesting enabling efficient charge transport. This work presents two new approaches to achieve higher photovoltaic performance for organic photovoltaic systems; thiol modification of the polymers for improved morphological features, and incorporation of ligand-free gold nanoparticles with surface plasmon absorption into the active layer to be stabilized by the covalent interaction with the thiol side groups of the polymers. To achieve this goal, a benzoxadiazole bearing polymer (POxT) and its bromine (POxT-Br) and thiol (POxT-SH) comprising derivatives were synthesized, their electrochemical, optical, photovoltaic, and morphological characterizations were performed. For photovoltaic characterizations, conventional device architecture of ITO/PEDOT:PSS/polymer:PC71BM/LiF/Al was utilized, where the POxT-SH showed the highest JSC and PCE values, 6.52 mA/cm2 and 2.71%, respectively. Gold nanoparticles were synthesized via laser ablation method, and upon incorporation, the PCE value was boosted to 3.29%, with an increase of 21.4% compared to POxT-SH comprising organic solar cells.
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    Enhanced confined microwave transmission by single subwavelength apertures
    (2005) Çağlayan, Hümeyra
    Grating-coupling phenomena between surface plasmons and electromagnetic waves are studied in the microwave spectrum using metallic circular apertures surrounded by an array of grooves. The measurements are performed in the microwave spectrum of 10-18 GHz, corresponding to a wavelength region of 16.7-30 mm. The metallic samples have a subwavelength hole with a diameter of 8 mm and have concentric grooves with a periodicity of 16 mm. We first present the experimental and theoretical results of enhanced microwave transmission though a subwavelength circular aperture with concentric periodic grooves around the surface plasmon resonance frequency. This is followed by transmission studies through circular annular apertures with and without concentric periodic grooves around the aperture. We demonstrate a 145-fold enhancement factor could be obtained with a subwavelength circular annular aperture surrounded by concentric periodic grooves. Moreover, we study the diffraction of electromagnetic waves from subwavelength metallic circular annular apertures in the microwave spectrum. The theoretical and experimental demonstration of the near- and far-field EM distributions for subwavelength circular apertures and circular annular apertures surrounded by concentric periodic grooves is reported. We present the angular transmission distributions from circular apertures and circular annular apertures surrounded by concentric periodic grooves. At the surface mode resonance frequency the transmitted electromagnetic waves from the subwavelength circular annular aperture surrounded by concentric periodic grooves have a strong angular confinement with an angular divergence of ±3°. This represents a fourfold reduction when compared to the angular divergence of the beam transmitted from a subwavelength aperture. These results show, that not only high transmission but also a confined beam is achieved at the surface plasmon resonance frequency using a circular annular aperture with grooves .
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    Hybridization of fano and vibrational resonances in surface-enhanced infrared absorption spectroscopy of streptavidin monolayers on metamaterial substrates
    (2014) Alici, K. B.
    We present spectral hybridization of organic and inorganic resonant materials and related bio-sensing mechanism. We utilized a bound protein (streptavidin) and a Fano-resonant metasurface to illustrate the concept. The technique allows us to investigate the vibrational modes of the streptavidin and how they couple to the underlying metasurface. This optical, label-free, nonperturbative technique is supported by a coupled mode-theory analysis that provides information on the structure and orientation of bound proteins. We can also simultaneously monitor the binding of analytes to the surface through monitoring the shift of the metasurface resonance. All of this data opens up interesting opportunities for applications in biosensing, molecular electronics and proteomics. © 2014 IEEE.
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    InGaN green light emitting diodes with deposited nanoparticles
    (Elsevier BV, 2007) Butun, B.; Cesario J.; Enoch, S.; Quidant, R.; Özbay, Ekmel
    We grew an InGaN/GaN-based light-emitting diode (LED) wafer by metal-organic chemical vapor deposition (MOCVD), fabricated devices by optical lithography, and successfully deposited ellipsoidal Ag nano-particles by way of e-beam lithography on top. The diodes exhibited good device performance, in which we expected an enhancement of the radiated intensity by the simulations and emission measurements. The obtained results showed the feasibility of plasmon-assisted LED emission enhancement.
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    Plasmonic structures with extraordinary transmission and highly directional beaming properties
    (Wiley Periodicals, 2006) Cağlayan, H.; Bulu, I.; Özbay, Ekmel
    We studied the grating-coupling phenomena between surface plasmons and electromagnetic waves in the microwave spectrum. We first present the experimental and theoretical results of an enhanced microwave transmission though a subwavelength circular annular aperture with and without metallic gratings. We demonstrate that a 145-fold enhancement factor could be obtained with a subwavelength circular annular aperture that was surrounded by periodic metallic gratings. This was assisted by the guided mode of the coaxial waveguide and by coupling to the surface plasmons. We present the angular transmission distributions from circular annular apertures, and circular annular apertures surrounded by concentric periodic grooves. At the surface mode resonance frequency, the transmitted electromagnetic waves from the subwavelength circular annular aperture surrounded by concentric periodic grooves have a strong angular confinement with an angular divergence of ±3°. We demonstrate that only the output surface is responsible for the beaming effect. Furthermore, we present the field distributions and showed that there is no beaming effect at the off-resonance frequency. © 2006 Wiley Periodicals, Inc.
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    Plasmonically enhanced hot electorn based optoelectronic devices
    (2015-06) Atar, Fatih Bilge
    Hot electron based optoelectronic devices have been regarded as cost-e ective candidates to their conventional counterparts. The efficiency of conventional optoelectronic devices that rely on semiconductor photo-absorbers are mainly limited by the energy bandgap of the semiconductor. On the other hand, hot electron devices can overcome this limitation via the \internal photoemission" mechanism. Absorbed photons give their energy to free electrons of the metal and these high energy (\hot") electrons can be used to generate photocurrent in proper device configurations. High optical re ection from metals has remained as the main drawback of this photocurrent generation scheme but this problem has recently been addressed by the use of surface plasmons. Optical energy can be tightly confined to a metal layer or metal nanostructures in the form of surface plasmons, and the decay of surface plasmons in metals generates hot electrons. In this work, we study mechanisms of surface plasmon excitation, surface plasmon decay, hot electron generation and hot electron photoemission for photocurrent generation. We demonstrate novel device architectures and plasmon excitation structures. We demonstrate the use of such layers for plasmon enhanced hot electron based photodetectors and photovoltaic devices. A metal-semiconductor Schottky junction diode structure is used as hot electron photodetector. A double metal-insulator-metal (MIM) architecture is proposed as a hot electron photovoltaic device. Full wave electromagnetic simulations of these device structures are conducted to provide insight into the surface plasmon assisted hot electron generation process and give future directions in this field.
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    Resonant excitation of surface plasmons in one-dimensional metallic grating structures at microwave frequencies
    (Institute of Physics Publishing, 2005) Akarca-Biyikli, S. S.; Bulu, I.; Özbay, Ekmel
    Grating-coupling phenomena between surface plasmons and electromagnetic waves were studied in the microwave spectrum using metallic gratings. Transmission measurements were carried out to observe the transmitted radiation around the surface plasmon resonance frequencies. Grating structures with subwavelength apertures were designed for transmission experiments. Measurements were made in the microwave spectrum of 10-37.5 GHz, corresponding to a wavelength region of 8-30 mm. The A1 samples had a grating periodicity of 16 mm. A 2 mm wide subwavelength slit was opened for transmission samples. Samples with one/double-sided gratings displayed remarkably enhanced transmission and directivity with respect to the reference sample without gratings. The experimental results agreed well with theoretical simulations. ∼50% transmission at 20.7 mm, ∼25-fold enhancement, and ±4° angular divergence were achieved with a ∼λ/10 aperture.
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    Tuning plasmon induced reflectance with hybrid metasurfaces
    (MDPI AG, 2019-03) Habib, M.; Özbay, Ekmel; Çağlayan, Hümeyra
    Electrically tunable metasurfaces with graphene offer design flexibility to efficiently manipulate and control light. These metasurfaces can be used to generate plasmon-induced reflectance (PIR), which can be tuned by electrostatic doping of the graphene layer. We numerically investigated two designs for tunable PIR devices using the finite difference time-domain (FDTD) method. The first design is based on two rectangular antennas of the same size and a disk; in the second design, two parallel rectangular antennas with different dimensions are used. The PIR-effect was achieved by weak hybridization of two bright modes in both devices and tuned by changing the Fermi level of graphene. A total shift of ∼362 nm was observed in the design with the modulation depth of 53% and a spectral contrast ratio of 76%. These tunable PIR devices can be used for tunable enhanced biosensing and switchable systems.