An Integrated Optical Waveguide Thermo-optic Tunable Filter Electrode Research And Design

In modern optical communication system, WDM (Wavelength Division Multiplexing)is widely used. As an important part of WDM system, optical filter is the key device in all-optical communication in the future. Among present optical filter researches, waveguide resonators based on PLC (Planar Light-wave Circuit) fabrication technics gain much attention.This paper concentrates on the analysis on the electrode of a new type of waveguide ring resonator with thermal tuning. The device uses Er³⁺/Yb³⁺ co-doped phosphate glass as substrate, which can amplify optical signal at 1550 nanometer so that to compensate the transmission loss in the waveguide. By covering a thin metal film on the waveguide as heat source, thermal-optical effect can be used to tune up the filtering wavelength of the device.Main work of the paper includes:1. First, a heat-field calculation model of the electrode is built based on heat conduction theory. Using principle of superposition, we get the analytical expression of temperature in the device and discuss the factors which influence the temperature distribution. Then, compared with single electrode, a type of bi-electrode model is put forward and we demonstrate its superiority in temperature equality.2. For complex-shape electrode such as arc-shape, finite difference method (FDM) is introduced and the best solving method is determined through discussion. Through simulation comparison between numerical method and analytical method, limitation is found in analytical method. Then, temperature difference is shown between arc-shape electrode and rectangle electrode. Next, the temperature responsing curve of the device with time is drawn through time-domain finite difference method and we tell the factors which can improve the temperature response of the device.3. As temperature distribution of the device has been known well, we analyze the filtering curve change under thermo-optical effect in the device based on F-P filtering theory. Then, consider with the excursion between electrode and ring resonator in fabricating process, we discuss the change of filtering peak-wavelength with excursion and other factors of electrode.4. Experimental work is focused on the fabrication of electrode and waveguide. First, thickness and material of electrode and the buffer layer are confirmed separately. Then, vacuum-evaporation technics is used to deposit Al film on the waveguide. Next, the fabrication of planar and channel waveguide using ion exchange is developed. Through effective index analysis, we find out how time and temperature in ion exchange influence refractive index of waveguide. At the end, mask graphics for both of ring resonator and electrode are designed and fabricated.In all, theoretical work of this paper gives a model for thermo-optical effect analysis in phosphate glass, which builds a foundation for more precise theoretical research in the future. In experimental work, researches on fabrication of electrode and waveguide both make convenience for further experiment and fabrication of the device on phosphate glass.