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Microring Resonators And Photodetectors With SU-8 Optical Waveguides On Silicon

Posted on:2016-05-21Degree:DoctorType:Dissertation
Country:ChinaCandidate:L JinFull Text:PDF
GTID:1108330464954338Subject:Optical communication technology
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As optical communication and optical sensing technology progress rapidly, the integrated photonic devices attract more and more interest due to its high compactness and miniaturization. Among all kinds of integrated optical materials, polymer shows superior performances in terms of cost reduction and low loss. Besides, polymer has a very high thermal-optical coefficient, which is good for optical switch and nonlinear effect. In this paper we design and fabricate two kinds of mircoring resonator based on SU-8 polymer, and we also explore the nonlinear effect of microring based on high thermal-optical effect. And we do research on suspended waveguide silicon photondetector because SU-8 has low absorption loss during visible wavelength and silicon can work as detector material during visible wavelength. Based on waveguide photondetector we design and fabricate integrated sensor which combine SU-8 and silicon.The fundamentals of optical waveguides are briefly reviewed and a few n μ merical calculation methods are introduced. First, the theory of wave equation is introduced and according to this theory the slab waveguide modes can be solved analytically and the channel waveguide modes can be solved approximately. In order to solve the modes of waveguide accurately, n u merical calculation is a good method. Then some n μ merical simulation methods like beam propagation(BPM), finite difference method (FDM) and finite-difference time-domain (FDTD) method are introduced one by one.A novel microring resonator is presented, the coupling region is based on 2×2 angled multimode interference(MMI) coupler. Unlike the standard MMI with fixed splitting ratio, in the angled MMI, continuous variable splitting ratio can be got by changing the bending angle. The Q of the angled MRR is up to 25000 when the bending angle is 3.25 degree. In addition, the fabrication tolerance of MMI is high and there is no need to use high resolution equipment that is used in the fabrication of directional coupler (DC). In the end, the test results and the simulations match well.Ridge waveguide with slab has very low loss and we design a race-track MRR with based on this waveguide. The coupling region of the MRR is DC which is quite easy for coupling due to the thick slab and the common contact UV lithography can meet the requirements of fabrication process. The whole process consists of twice spin coating and twice lithography without etch process avoiding the roughness which the etch process brings. A series of MRRs with different coupling coefficients are fabricated, the Q value as high as 34700. Thermal-optical nonlinear effect of the MRR is explored and the resonant wavelength is shifted when the input power is high. Based on that, we do research on optical bistability. Comparing the experimental results with the simulations, they match very well.The suspended waveguide photodetector is designed and fabricated based on silicon substrate due to that the SU-8 waveguide has a low absorption loss and the silicon works as active material. Then through the improved design, the length of electrode decrease to 150 μ m from 710 μ m and the dark current is improved to 200nA@2.45V from 4.39uA@5V, meanwhile the responsibility increase to 0.326A/W from 0.232A/W. In addition, integrated sensor is fabricated and the photon current increase remarkably when the sensing component is placed from air to ethyl alcohol environment.
Keywords/Search Tags:Polymer Device, MRR, Angled MMI, Ridge Waveguide, Race-Track MRR, Nonlinear Effect, Suspended waveguide Photodetector, Metal-Semiconductor-Metal Photodetector, Integrated Sensor
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