Browsing by Subject "Plasmons (Physics)."

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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.
Open Access
Surface plasmon based enhanced transmission of electromagnetic waves
(2004) Bıyıklı, Süheyla Sena Akarca
Grating-coupling phenomena between surface plasmons and electromagnetic waves are studied in the microwave spectrum using metallic gratings. Transmission and reflection measurements were carried out to observe the transmitted and reflected radiation around the surface plasmon resonance frequencies. Grating structures with subwavelength apertures were designed for transmission experiments. Measurements were done in the microwave spectrum of 10−37.5 GHz, corresponding to a wavelength region of 8−30 mm. The Al samples had a grating periodicity of 16 mm. A 2 mm-wide subwavelength slit was opened for transmission samples. Samples with one/double-sided gratings displayed remarkably enhanced transmission and directivity with respect to the reference sample without gratings. The experimental results agreed well with theoretical simulations. ~50% transmission at 20.7 mm, ~25-fold enhancement, and ±4° angular divergence was achieved with a ~λ/10 aperture. Reflection measurements of one-sided grating sample resulted in clear observation of surface plasmon coupling phenomena. Reflectivity peaks were measured around theoretically calculated resonance frequencies.