Research On Sensitivity Enhancement For Optical Waveguide Lightmode Spectroscopy(OWLS)

This thesis focuses the research on sensitivity enhancement for Optical Waveguide Lightmode Spectroscopy(OWLS) based on the theory of planar waveguides.First, in order to find a more effective method monitoring biochemical reaction timely for planar waveguides, the more intuitionistic cut-off characteristic of three-layer and four-layer planar waveguides is studied. After analysis, the limitation of three-layer waveguides is pointed out. Then a sketch map of four-layer waveguides is designed. Which is composed of air gap, polarizing polymer layer, high index waveguides layer and cover medium(analytes) that is being monitored timely; laser is coupled by prism and the index of polarizing polymer layer is controlled by electricity. Based on the sketch map, the theoretical analysis is presented. It is a useful sensor and the formula for it is presented. Finally, a computer program is generated to paint the sensitivity curves for different model systems, and the classical evanescent-waveguide biosensors are compared with them. The result shows that higher sensitivity can be achieved with thicker waveguides.Second, we noticed that the planar waveguides sensors with reverse-symmetry have higher sensitivity than that with normal symmetry, which demonstrated it by accurate formula. A new design is presented, aiming to arrive at high sensitivity (between 0.2 and 0.9) of dynamic monitoring for reverse-symmetry planar optical waveguides biosensors. The design is based on a new material, a line of Teflon AF resins with available index of refractions of 1.29(2400), which is regarded as the only candidate for substrate. By theoretical analysis, we get two groups of parameters that must be taken into consideration in the process of design: one is that, when the material of the waveguides film is already chosen, we get the possible maximum cover refractive index change and parameters of the film thickness; the other is that, when we make the sensor's maximum cover refractive index change suit definite requirement, we get and the minimum of the refractive index of waveguides film and parameters of the film thickness. Two groups of simulating results are given as examples by computer calculation.