Browsing by Subject "Filter"

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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
Low-voltage current-mode CMOS filter structure for high frequency applications
(1995) Karşılayan, Aydın İlker
In this thesis, a new method for the design of tunable current-mode CMOS filters is presented. The proposed structure is suitable for low-voltage (3V) and high frequency applications. Basic building blocks are differential damped integrator and differential damped differentiator, which have tunable comer frequencies. Using first order building blocks and applying feedback techniques, biquadratic sections of low-pass, high-pass and band-pass filters are generated. Higher order filters are implemented by using cascaded biquad synthesis. Filters are tuned by means of two control voltages, from 50% to 130% of their corner frequencies. HSPICE simulations show that filter implementation up to 0.5GHz is possible for 2.4^ CMOS technology. The available frequency range can be increased using a better technology such as 0.7/i CMOS. Layouts for two test chips are generated using CADENCE full-custom design environment for 0.7/i and 2.4/i CMOS processes.