Polymer Waveguide Tunable Microring Filter Based On Thermo-optic Effect

Photonic integration is an inevitable trend of information transmission and processing technology such as the all-optical communications and photonic microwave signal processing. Integrated waveguide tunable optical filter is the core functional unit of large-scale photonic integrated systems, and it is important to reduce the power consumption and improve the tuning flexibility. In this paper, the design, fabrication, performance testing and optimization of the integrated waveguide microring tunable optical filter is presented. The completed works are as follows.According to the validity analysis of one-dimensional and two-dimensional models of waveguide thermo-optic device, the latter is selected to analyze the device’s thermal action. The Laplace equation and boundary conditions of the dependence of refractive index change on thermo-optical effect is derived. And the process of the thermo-optic effect simulation with the commercial softwares is presented.In order to improve the tuning flexibility of microring filter, the MZI based tunable coupler is introduced to substitute the traditional directional coupler. The additional phase shift produced simultaneously as the coupling coefficient tuning with MZI is analyzed. And the tuning range of the equivalent coupling coefficient affected by the splitting ratio deviation from the perfect splitting of3dB is also investigated. The tunable polymer waveguide microring filter is designed and the preliminary waveguide device is fabricated with UV-based soft imprint technology.The performance of the fabricated polymer waveguide microring tunable filter is investigated. With changing the current of the electrode on the microring waveguide, the resonant wavelength of the filter is tuned and the tuning efficiency is about7.73pm/mW. The resonant wavelength shifts to the short wavelength as increasing the current. The three coupling conditions of over-, critical-and under-coupling are realized by adjusting the current of the electrode on the MZI’s arm. Then the loss property of the polymer wavguide tunable filter is analyzed.In order to reduce the power consumption of the tunable optical filter, the thermal isolation trenches (TITs) are introduced beside the electrode. With a2×2MZI tunable coupler as the example, the influence of the up-cladding thickness on the guided wave propagation loss and the thermo-optic phase tuning efficiency is analyzed. The position of TITs is optimized which can influence the tuning power consumption and the mode mismatch loss. Moreover, the taperd TITs is proposed to decrease the mode mismatch loss. Finally, the mask of polymer waveguide tunable filters with tapered TITs is designed.