Browsing by Subject "Grating Coupling"

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Open Access
Coupled surface plasmon structures and applications
(2009) Gürel, Kemal
Surface plasmons have attracted great interest during past decades due to their unique physical properties. In this thesis, we study grating-coupled surface plasmons for sensing and filtering applications. We first present simple physical and chemical procedures that allow tuning and modification of the topography of gratings present in optical storage discs into geometries optimal for grating coupled plasmon resonance excitation. After proper metal coating, the tuned surfaces exhibit sharp plasmon resonances that can be excited at wavelengths ranging from 260 nm to over 2.7 µm with relatively high quality factors. As an immediate exemplary application, use of such optimized gratings in aqueous medium for refractive index measurement is demonstrated. We also report another plasmonic component based on a pair of surfaces displaying grating coupled plasmon enhanced transmission. We observe high quality factor transmission peaks as high as 100 through our plasmonic filter based on gratings obtained directly from optical storage disks. Wavelength and polarization dependent transmission is also demonstrated in the visible and infrared portions of the spectrum. The resonance wavelength of this filter can be tuned by simply changing the angle of incidence. Numerical calculations agree well with measurements. Our work can open up directions toward disposable optical components such as filters and polarizers. Morever, we investigate plasmonic force between two coupled metallic layers. We observe the mode splitting due to coupling between plasmonic surfaces by using finite difference time domain simulations.
Open Access
Microfluidics for plasmonic sensors
(2009) Ertaş, Yavuz Nuri
In this thesis, we integrate microfluidics with grating-coupled surface plasmon configurations for sensing applications. First, in order to observe optimal excitations, we introduce procedures for modification of the surface profiles of gratings acquired from commercially available optical storage disks. A must requirement in plasmonic systems, thin film metal deposition is performed. Soft lithographic techniques are applied to coated disks to transfer the surface topography of the disks to an elastomeric material, PDMS. Optical lithography is used to fabricate microfluidic channels to where fluid will be injected. After fabricating the final structure, ellipsometric measurement is used to investigate the device performance. Experimental results were in consistence with the theoretical simulations providing similar behaviours of reflection spectra. The resonance wavelengths are found to be occuring very near to the expected values along with high quality factors. However, to the device structure, an intensity loss is observed which can be further improved. We achieved the tuning of the resonance wavelength by changing the refractive index of the medium inside the microchannel. Integration of the microfluidic channel to surface plasmon studies may open up many applications such as biomolecular sensing.