Browsing by Subject "Metallic gratings"
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Item Open Access Directional selectivity through the subwavelength slit in metallic gratings(IEEE, 2011) Çakmakyapan, Semih; Çaglayan, Hümeyra; Serebryannikov, Andriy; Özbay, EkmelAn approach for obtaining strong directional selectivity through a single subwavelength slit in non-symmetric metallic gratings is shown theoretically and experimentally. Directionality effect originates from the different resonance frequencies of two interfaces. © 2011 OSA.Item Open Access Enhanced transmission of microwave radiation in one-dimensional metallic gratings with subwavelength aperture(American Institute of Physics, 2004) Akarca-Biyikli, S. S.; Bulu, I.; Özbay, EkmelWe report a theoretical and experimental demonstration of enhanced microwave transmission through subwavelength apertures in metallic structures with double-sided gratings. Three different types of aluminum gratings (sinusoidal, symmetric rectangular, and asymmetric rectangular shaped) are designed and analyzed. Our samples have a periodicity of 16 mm, and a slit width of 2 mm. Transmission measurements are taken in the 10–37.5 GHz frequency spectrum, which corresponds to 8–30 mm wavelength region. All three structures display significantly enhanced transmission around surface plasmon resonance frequencies. The experimental results agree well with finite-difference-time-domain based theoretical simulations. Asymmetric rectangular grating structure exhibits the best results with ,50% transmission at 20.7 mm, enhancement factor of ,25, and ±4° angular divergence.Item Open Access Experimental validation of strong directional selectivity in nonsymmetric metallic gratings with a subwavelength slit(American Institute of Physics, 2011-02-02) Cakmakyapan, S.; Caglayan, H.; Serebryannikov, A. E.; Özbay, EkmelStrong directional selectivity is theoretically predicted and experimentally validated at the microwave frequencies in the beaming regime for a single subwavelength slit in nonsymmetric metallic gratings with double-side corrugations. The operation regime can be realized at a fixed angle of incidence when the surface-plasmon assisted transmission is significant within a narrow range of observation angles, if illuminating one of the grating interfaces, and tends to vanish for all observation angles, if illuminating the opposite interface. The studied effect is connected with asymmetry (nonreciprocity) in the beaming that occurs if the surface plasmon properties are substantially different for the two interfaces being well isolated from each other.Item Open Access One-way transmission through the subwavelength slit in nonsymmetric metallic gratings(Optical Society of America, 2010-07-27) Cakmakyapan, S.; Serebryannikov, A. E.; Caglayan, H.; Özbay, EkmelAn approach for obtaining one-way transmission in the beaming regime is suggested that is based on the directional radiation of surface plasmons in nonsymmetric metallic gratings with a single slit. In contrast to the various nonsymmetric one-way diffraction gratings that have recently been proposed, the possibility of obtaining of narrow beams is demonstrated. Strong directional selectivity can appear a wide range of the observation angles, while the angle of incidence is retained.Item Open Access Plasmonic band gap structures for surface-enhanced Raman scattering(Optical Society of American (OSA), 2008) Kocabas, A.; Ertas G.; Senlik, S.S.; Aydınlı, AtillaSurface-enhanced Raman Scattering (SERS) of rhodamine 6G (R6G) adsorbed on biharmonic metallic grating structures was studied. Biharmonic metallic gratings include two different grating components, one acting as a coupler to excite surface plasmon polaritons (SPP), and the other forming a plasmonic band gap for the propagating SPPs. In the vicinity of the band edges, localized surface plasmons are formed. These localized Plasmons strongly enhance the scattering efficiency of the Raman signal emitted on the metallic grating surfaces. It was shown that reproducible Raman scattering enhancement factors of over 10 5 can be achieved by fabricating biharmonic SERS templates using soft nano-imprint technique. We have shown that the SERS activities from these templates are tunable as a function of plasmonic resonance conditions. Similar enhancement factors were also measured for directional emission of photoluminescence. At the wavelengths of the plasmonic absorption peak, directional enhancement by a factor of 30 was deduced for photoluminescence measurements. © 2008 Optical Society of America.Item Open Access Spoof-plasmon relevant one-way collimation and multiplexing at beaming from a slit in metallic grating(Optical Society of America, 2012) Çakmakyapan, Semih; Serebryannikov, A.E.; Caglayan H.; Özbay, EkmelDiode and collimator/multiplexer functions are suggested to be combined in one device that is based on a thin metallic grating with a single subwavelength slit. A proper choice of the structural (a)symmetry of the grating can result in obtaining one-way collimation and multiplexing with a single on-axis or off-axis, or two off-axis narrow outgoing beams. It is possible due to freedom in utilizing different combinations of the excitation conditions of the spoof surface plasmons at the four grating parts - right and left front-side and right and left back-side ones. Such a combining provides one with an efficient tool to engineer one-way collimators and multiplexers with the desired characteristics. Strong asymmetry in transmission with respect to the incidence direction (forward vs backward case) can be obtained within a wide range of variation of the incident beam parameters, i.e., angle of incidence and frequency, while the outgoing radiation is concentrated within a narrow range of the observation angle variation. Most of the observed asymmetric transmission features can be qualitatively explained using the concept of the equivalent source placed inside the slit. © 2012 Optical Society of America.Item Open Access Surface wave splitter based on metallic gratings with sub-wavelength aperture(Optical Society of American (OSA), 2008) Caglayan H.; Özbay, EkmelWe investigated the splitting of surface electromagnetic waves trapped at the output surface of a one-dimensional metallic grating structure. The output gratings of the structure asymmetrically such that the output surfaces at the different sides of the subwavelength aperture can support surface waves at different frequencies. The transmission amplitude as measured at the left side is 1,000 times of that at the right side at 16 GHz. At 24 GHz, the transmission measured at the right side is 20 times that of the left side of the structure. Therefore, surface waves are guided into the different sides of the aperture at different frequencies via metallic gratings. The experimental results are in agreement with the theoretical results. © 2008 Optical Society of America.Item Open Access Triangular metallic gratings for high efficiency thin film solar cells(IEEE, 2011) Battal, Enes; Yoǧurt, Alper Taha; Aygun, Levent Erdal; Okyay, Ali KemalOur design of novel nanometallic structure integrated with photovoltaic devices provides polarization insensitive, broadband and significantly high absorptivity enhancement. This structure attains absorptivities higher than compared to similar thickness of Silicon solar cells with gratings. © 2011 IEEE.Item Open Access Triangular metallic gratings for large absorption enhancement in thin film Si solar cells(Optical Society of American (OSA), 2012) Battal, E.; Yogurt, T.A.; Aygun L.E.; Okyay, Ali KemalWe estimate high optical absorption in silicon thin film photovoltaic devices using triangular corrugations on the back metallic contact. We computationally show 21.9% overall absorptivity in a 100-nmthick silicon layer, exceeding any reported absorptivity using single layer gratings placed on the top or the bottom, considering both transverse electric and transverse magnetic polarizations and a wide spectral range (280 - 1100 nm). We also show that the overall absorptivity of the proposed scheme is relatively insensitive to light polarization and the angle of incidence. We also discuss the implications of potential fabrication process variations on such a device. © 2012 Optical Society of America.Item Open Access Tunable surface plasmon resonance on an elastomeric substrate(Optical Society of American (OSA), 2009-05) Olcum, Selim; Kocabaş, Aşkın; Ertaş, Gülay; Atalar, Abdullah; Aydınlı, AtillaIn this study, we demonstrate that periods of metallic gratings on elastomeric substrates can be tuned with external strain and hence are found to control the resonance condition of surface plasmon polaritons. We have excited the plasmon resonance on the elastomeric grating coated with gold and silver. The grating period is increased up to 25% by applying an external mechanical strain. The tunability of the elastomeric substrate provides the opportunity to use such gratings as efficient surface enhanced Raman spectroscopy substrates. It's been demonstrated that the Raman signal can be maximized by applying an external mechanical strain to the elastomeric grating. © 2009 Optical Society of America.