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EBL Fabricated Plasmonic Nanostructures for Sensing Applications


Konum:  A311

Dr. Neval Cinel Abstract : Plasmonics is a major branch of photonics dealing with light-matter interactions in metallic nanostructures. Plasmonic devices provide extreme confinement of electromagnetic oscillations to very small volumes beyond diffraction limit at optical frequencies. The aim of the seminar is to demonstrate the utilization of plasmonics for several applications such as optical localized surface plasmon resonance (LSPR) biosensor design, enhancement of signal intensity in surface enhanced Raman spectroscopy (SERS) and absorption enhancement in photodetectors. Firstly, a sensor structure that detects the changes in the refractive index of the surrounding medium by optical transmission measurements is depicted. Secondly, tandem truncated nano-cones composed of Au-SiO2-Au layers that exhibit highly tunable double resonance behavior were shown to increase SERS signal intensity, for the first time. Another SERS substrate containing dual layer, periodic, “coupled” concentric rings, separated by a dielectric spacer provided Raman signal intensity 630 times larger than plain gold film and 8 times larger than an “etched” concentric ring structure. Finally, Al nanoparticles with plasmonic resonance at UV wavelengths fabricated in between the Schottky contacts of an MSM detector on semi-insulating GaN was shown to yield 1.5 fold enhancement in absorption and photocurrent collection. Plasmonic enhancement in UV was studied for the first time with this study. Another UV-MSM photodetector on GaN that includes subwavelength apertures surrounded by nano-structured metal gratings was compared to a conventional design without gratings. Results indicated an 8 fold enhancement in the photocurrent at the resonant wavelength.