Browsing by Author "Bek, Alpan"
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Article Citation Count: 8Enhanced second harmonic generation from coupled asymmetric plasmonic metal nanostructures(Iop Publishing Ltd, 2015) Yıldız, Bilge Can; Tasgin, Mehmet Emre; Abak, Musa Kurtulus; Coskun, Sahin; Unalan, Husnu Emrah; Bek, Alpan; Airframe and Powerplant MaintenanceWe experimentally demonstrate that two coupled metal nanostructures (MNSs), a silver nanowire and bipyramid, can produce similar to 30 times enhanced second harmonic generation compared to the particles alone. We develop a simple theoretical model, presenting the path interference effects in the nonlinear response of coupled MNSs. We show that the reason for such an enhancement can be the occurrence of a Fano resonance due to the coupling of the converter MNS to the long-lived mode of the attached MNS.Conference Object Citation Count: 16A feasibility study for controlling self-organized production of plasmonic enhancement interfaces for solar cells(Elsevier Science Bv, 2014) Güllü, Seda Kayra; Gullu, Seda Kayra; Es, Firat; Demircioglu, Olgu; Gunoven, Mete; Turan, Rasit; Bek, Alpan; Physics GroupThe decoration of metal nanoparticles (MNPs) by the self-organized mechanism of dewetting is utilized as a suitable method for plasmonic interface integration to large area full-scale solar cell (SC) devices. Reflection measurements are performed on both flat and textured silicon (Si) SCs in order to investigate the local plasmonic resonances of the MNPs. The effects of particle size and thickness of silicon nitride (Si3N4)anti-reflection coating layer are investigated by reflection measurements and the shift of plasmon resonance peak position. It is found that surface roughness, annealing time, annealing temperature, and varying Si3N4 thickness can be used as mechanisms to control the size distribution, shape of the resultant nano-islands, and SC efficiency. The findings on the most suitable nanoparticle system production parameters by this method, depends on the applied substrate properties which are expected to guide further applications of plasmonic interfaces and also to the other kinds of device structures in the ultimate quest for attaining affordable high efficiency SCs. (C) 2013 Elsevier B.V. All rights reserved.Article Citation Count: 22Silent enhancement of SERS signa without increasing hot spot intensities(Walter de Gruyter Gmbh, 2018) Yıldız, Bilge Can; Yildiz, Bilge Can; Bek, Alpan; Tasgin, Mehmet Emre; Airframe and Powerplant MaintenancePlasmonic nanostructures enhance nonlinear response, such as surface enhanced Raman scattering (SERS), by localizing the incident field into hot spots. The localized hot spot field can be enhanced even further when linear Fano resonances take place in a double resonance scheme. However, hot spot enhancement is limited with the modification of the vibrational modes, the breakdown of the molecule, and the tunneling regime. Here, we present a method which can circumvent these limitations. Our analytical model and solutions of 3D Maxwell equations show that: enhancement due to the localized field can be multiplied by a factor of 10(2)-10(3). Moreover, this can be performed without increasing the hot spot intensity which also avoids the modification of the Raman modes. Unlike linear Fano resonances, here, we create a path interference in the nonlinear response. We demonstrate on a single equation that enhancement takes place due to cancellation of the contributing terms in the denominator of the SERS response. Our method can be implemented on an atomic force microscope tip, decorated (or "contaminated") with appropriate quantum emitters.