Design Of Periodic-polarized Electro-optic Filter And Au Nanoparticle LSPR Optical Sensor

Tunable optical filter, which is a very important component of the opticalcommunication system, has been widely used in the multiplex/demultiplex, add dropmultiplex (ADM), dispersion compensation of the optical signals. Espcecially, themulti-wavelength tuanable is paid lots of attention on due to its large flexibility.Combined with our topic source, an electro-optic tunable multi-wavelegnth filter isdesigned for the node of the wavelength division multiplexing (WDM) network.With the development of the modern micro-nano fabrication technology,localized surface plasmon resonance (LSPR) effect of the metal nano structures hasbeen paid a lot of attention on. Due to its own special optic characteristic, LSPR effectof metal nano structures has been well studied for the use of optic waveguide,biochemical sensor, optic antenna, and optic couplers etc., so as to largely reduce thesize of the devices. In the thesis, combined with our topic source, kinds of metalnanostructures have been well studied, including their theoretical LSPR principles andexperimental biosensor application.The main work and innovations are listed below.1. An electro-optic tunable filter is designed for the node of the WDM network.Based on x-cut, y-propagation Ti-diffused LiNbO3waveguide, polarizationconversion is controlled by an N-stage cascade of alternating interdigital andphase-shifted electrodes. The concept of finite impulse response (FIR) digital filteringis used to calculate the input voltages in the z field, which control the mode couplingand phase shift respectively. By changing the input voltages, a wavelength-tunablebandpass filter or a non-periodic multi-wavelength selector can be obtained.2. The LSPR effect of metal nanostructures is systematically simulated studied,including the effects of material, size, shape, and distribution of the nanostructures onits optical spectrum. Fano resonances are investigated in nanobars with symmetriclengths and side-by-side assembling in the visible and near infrared (NIR) region. Ifthe direction of input electric field is parallel to the short axis of the nanobar, singleFano resonance can be obtained in nanobar dimer, furthermore, double Fanoresonacnes are shown in side-by-side assembled nanobar trimer with asymmetric gaps.Fano resonance is induced by the near-field coupling of the LSPR modes, so as to show high refractive index sensitivity, figure of merit (FOM), and large lightextinction in periodic array of assembled nanobars, which can be potentially used inmulti-wavelength biosensor. It shows that FOM is up to20, and the full width at halfmaximum (FWHM) is down to50nm.3.60and500nm dia. Au nano disk arrays are fabricated on glass substratesusing nanosphere lithography (NSL). Polystyrene (PS) spheres with different sizes areself assembled on the Au film to form a uniform single layer PS mask, followed bythe plasma etching of the Au to get the Au disk arrays.4. The fabricated60and500nm dia. Au disk arrays on the glass substrates areused for the detection of the human-derived retinal pigment epithelial RPE-1cell andbreast cancer MCF-7cell. It shows the detection range of the cell concentration canreach104-106cells/ml. The influences of the characteristic and morphology of thefixed cells which are corresponding to the refractive index of the surrounding mediaof the Au disks on the detection of the cell concentration are compared, as well as thesize of the Au disk which is corresponding to the electric field decay length. Theresults shown here is very useful for the optimization of the Au disk selection for theparticular cell type.5. SiO2\Au disk arrays with90nm dia. and160nm period are fabricated on Aunano film which is evaporated on glass substrates. The coupling between the LSPRmode of the Au disks and the surface plasmon polarization (SPP) mode of the Au filmcan not only enhance the intensity of the localized electric field, but also inducemultiple resonance wavelengths, which can be used in the multi-wavelength detectionof the cell concentration with larger sensitivity. MCF-7cells are detected with thefabricated sensors, and the lowest concentration of2.14×103cells/ml are shown,which is lower than the shown results~104cells/ml of the500nm dia. Au disks onglass substrates. Multi-wavelength detection can reduce the detection error of thesingle type of cells, furthermore, it can be potentially used in the detection of multicell types.