Browsing by Subject "Plasmonic resonances"

Now showing 1 - 3 of 3

Open Access
Plasmonic materials based on ZnO films and their potential for developing broadband middle-infrared absorbers
(American Institute of Physics Inc., 2014) Kesim, Y.E.; Battal, E.; Okyay, Ali Kemal
Noble metals such as gold and silver have been extensively used for plasmonic applications due to their ability to support plasmons, yet they suffer from high intrinsic losses. Alternative plasmonic materials that offer low loss and tunability are desired for a new generation of efficient and agile devices. In this paper, atomic layer deposition (ALD) grown ZnO is investigated as a candidate material for plasmonic applications. Optical constants of ZnO are investigated along with figures of merit pertaining to plasmonic waveguides. We show that ZnO can alleviate the trade-off between propagation length and mode confinement width owing to tunable dielectric properties. In order to demonstrate plasmonic resonances, we simulate a grating structure and computationally demonstrate an ultra-wide-band (4-15 μm) infrared absorber. © 2014 Author(s).
Open Access
Resonance broadening and tuning of split ring resonators by top-gated epitaxial graphene on SiC substrate
(AIP Publishing LLC, 2013) Cakmakyapan, S.; Sahin, L.; Pierini, F.; Strupinski, W.; Özbay, Ekmel
Split ring resonators (SRRs) are subwavelength structures that are able to localize and enhance the electromagnetic wave. Controlling the plasmonic resonance behavior of metallic nanostructures, such as SRRs, plays an important role in optoelectronics and nanophotonics applications. Electrically tunable carrier concentration of graphene provides hybrid devices, where the plasmonic structures and graphene are combined. In this paper, we report the design, fabrication, and measurement of a device comprising a SRR array on epitaxial graphene. We obtained resonance broadening and tuning of split ring resonators by utilizing an epitaxial graphene transistor with transparent top-gate.
Open Access
Simple and complex metafluids and metastructures with sharp spectral features in a broad extinction spectrum: particle-particle interactions and testing the limits of the Beer-Lambert law
(American Chemical Society, 2017) Besteiro, L. V.; Gungor K.; Demir, Hilmi Volkan; Govorov, A. O.
Metallic nanocrystals (NCs) are useful instruments for light manipulation around the visible spectrum. As their plasmonic resonances depend heavily on the NC geometry, modern fabrication techniques afford a great degree of control over their optical responses. We take advantage of this fact to create optical filters in the visible-near IR. Our systems show an extinction spectrum that covers a wide range of wavelengths (UV to mid-IR) while featuring a narrow transparency band around a wavelength of choice. We achieve this by carefully selecting the geometries of a collection of NCs with narrow resonances that cover densely the spectrum from the UV to the mid-IR except for the frequencies targeted for transmission. This fundamental design can be executed in different kinds of systems, including a solution of colloidal metal NCs (metafluids), a structured planar metasurface, or a combination of both. Along with the theory, we report experimental results, showing metasurface realizations of the system, and we discuss the strengths and weaknesses of these different approaches, paying particular attention to particle-particle interaction and to what extent it hinders the intended objective by shifting and modifying the profile of the planned resonances through the hybridization of their plasmonic modes. We found that the Beer-Lambert law is very robust overall and is violated only upon aggregation or in configurations with nearly touching NCs. This striking property favors the creation of metafluids with a narrow transparency window, which are investigated here.