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Cataloged from PDF version of thesis. Includes bibliographical references (leaves 111-134). Thesis (Ph. D.): Bilkent University, Materials Science and Nanotechnology Program, İhsan Doğramacı Bilkent University, 2015. Recent advances in nanofabrication and characterization methods have enabled the study of novel optical phenomena, thus boosting the research in nanophotonics and plasmonics. Metal nanostructures offer a route for the excitation of surface plasmons by confining the light in sub-wavelength dimensions, yielding extremely high electromagnetic field intensities. Moreover, coupling different plasmon modes offers a rich optical dispersion which cannot be obtained inherently by using single plasmonic resonator. In this thesis, we first present a detailed study of simple coupled plasmonic structures based on metal-insulator-metal structure. Then, we use similar structures to devise novel optical platforms in various applications such as surface enhanced Raman spectroscopy (SERS), surface enhanced infrared absorption spectroscopy (SEIRA) and plasmon enhanced hot-electron devices. The first part of this thesis concentrates on coupled plasmonic structures and their spectroscopy and photodetector applications. Firstly, we study these structures numerically and analytically and show surface enhanced Raman spectroscopy (SERS) as a possible application with uniform signal intensities over large areas. Then, fabricating these plasmonic surfaces with sub-10nm gaps over large areas lead to development of single molecule Raman spectroscopy platforms. As an energy related application, a contact free characterization method is developed to probe hot electrons where similar coupled plasmonic surfaces are employed as hot electron devices. Finally, using aluminum and its native aluminum oxide hierarchical plasmonic surfaces are fabricated and its spectroscopy applications are demonstrated. In the second part of, we develop interference-coating-based sensing platforms in the visible and infrared wavelengths. Despite large field enhancements, plasmonic structures suffer from low signal intensities due to low mode volumes. To overcome this issue we propose another strategy, namely using interference coatings with small and uniform electric field enhancements over large mode volumes. These surfaces outperform the conventional plasmonic surfaces when they are used as infrared absorption spectroscopy platforms. Finally, similar surfaces are employed as colorimetric sensor platforms to sense monolayer and bilayer proteins simply by change in the surface color. by Sencer Ayas. Ph.D.

Plazmon polariton terimi iletkenlerdeki plazma elektronik salınımlarıyla çiftlenmiş elektromanyetik dalga modlarını tanımlamak için kullanılmaktadır. Yüzey plazmon rezonansları son yirmi 30 yilda nanofotonikten ve biyolojik algılamaya kadar birçok alanda geniş merak uyandırmıstır. Bu tezde, plazmon modlarını destekleyen metal yüzeylerin sebep oldugu ışınım ve emilim arttıtrımı lokal elektromanyetik mod yoğunluğuna göre incleledik. Serbest uzay elektromanyetik modlarını, plazmon modlarına çiftleyen değişik uyarılma mekanizmalarını teorik ve deneysel olarak inceledik. Dipollerdeki ışınım ve emilim plazmonik yapıların lokal mod yoğunluğu ve alan arttrımına bağlı olarak çeşitli oryantasyondaki ve plazmonik yapıların değişik yerlerindeki dipollerle inceledik. Kırınım ağına çiftlenmiş plazmon rezonansları RCWA ve FDTD metodlarıyla incelenmiştir. Rhodamine 6G boyasının emilim ve ışınım arttırımı plazmonikyapılarda deneysel olarak gösterilmiştir.Ayrıca konfokal raman mikroskobu florasans karakterizasyounda kullanılmıştır. Teorik sonuçşar ve deneysel sonuçlar birbirini destekler niteliktedir. Ayrıca boya moleküllerinin ışınımının plazmonik kırınım ağı yapılarında yöne bağımlılığı gösterilmiştir. Plazmon arttırımlı ışınım ve emilim uygulama alanları olaraksa, çok hassas emilim spektroskopisi, ince film güneş pillerinde performans arttırımı ve ışıyan yoğunlaştırıcılar olarak gösterilebilir. The term plasmon-polariton is used to describe coupled modes of electromagnetic waves with electronic plasma oscillations in conductors. Surface plasmon resonances have found profound interest over the last few decades in multiple fields ranging from nanophotonics to biological sensing. In this thesis, we study enhancement of absorption and emission of radiation due to the presence of a modified local electromagnetic mode density within the vicinity of metallic surfaces supporting plasmon modes. Various coupling schemes of free-space electromagnetic modes to plasmon modes are investigated theoretically and experimentally. Local mode densities and field enhancements due to plasmon modes in planarstructures, gratings and optical antennas have been studied in their relation to the absorption and emission enhancement of dipoles positioned in various orientations and locations with respect to structures displaying plasmonic effects. Particularly, grating coupled plasmon resonances were analysed using Rigorously Coupled Wave Analysis and Finite Difference Time domain methods. Experimental demonstrations of absorption and emission enhancement of dielectric layers containing Rhodamine 6G on various plasmonic structures are given. Confocal Raman microscopy was used in characterization of fabricated structures. It is seen that the experimental measurements are in good agreement with theoretical predictions. Direction dependent luminescence enhancement is observed with dye molecules on grating structures. Potential applications of plasmon enhanced absorption and emission include high sensitivity absorption spectroscopy, performance enhancement in thin film solar cells and luminescent concentrators. 100

Label free imaging of the chemical environment of biological specimens would readily bridge the supramolecular and the cellular scales, if a chemical fingerprint technique such as Raman scattering can be coupled with super resolution imaging. We demonstrate the possibility of label-free super-resolution Raman imaging, by applying stochastic reconstruction to temporal fluctuations of the surface enhanced Raman scattering (SERS) signal which originate from biomolecular layers on large-area plasmonic surfaces with a high and uniform hot-spot density (> 10(11)/cm(2), 20 to 35 nm spacing). A resolution of 20 nm is demonstrated in reconstructed images of self-assembled peptide network and fibrilated lamellipodia of cardiomyocytes. Blink rate density is observed to be proportional to the excitation intensity and at high excitation densities (> 10 kW/cm(2)) blinking is accompanied by molecular breakdown. However, at low powers, simultaneous Raman measurements show that SERS can provide sufficient blink rates required for image reconstruction without completely damaging the chemical structure.