Research Of The Mechanism And Key Technology Of Smoothing Surface Based On Silicon-on-insulator Optical Resonators

Optical resonators based on SOI (Silicon-on-insulator,SOI) have been widely applied inoptical communication, optical interconnection, high sensitivity sensors and other relatetechnical fields due to the characteristics of high integration, low power consumption andhigh sensitivity, which have important practical significance and potential application value.While the sidewall of the waveguide is roughness inevitably due to the preparation processthus leading to larger scattering loss and seriously restricting the realization of opticalresonators with large size and high quality factor Q (Quality Factor). Therefore, we make thediscussion centered around the mechanism of surface smoothing, aiming to find theoptimization methods which could reduce waveguide sidewall roughness and improve thequality factor.First of all, the coupling transmission theory of optical micro cavity is analyzed indetail, and we introduce several important indexes to measure the resonant characteristics ofoptical resonators. This paper reveals the generating mechanism of the sidewall roughnessfrom the point of preparation process, and theoretically analyses the influence of surfaceroughness on the transmission loss and the resonant characteristics of optical resonators.Secondly, we fabricate the SOI ring-type and track-type resonators through the MEMS(Micro-electro-mechanical-systems) technology, and briefly describe the the preparationprocess. According to the analysis of the principle of high temperature thermal oxidationprocess and its advantage on waveguide sidewall smoothing, we work out the programmes ofSingle-oxidation and double-oxidation processes Through the removal of metal mark,oxidation and the subsequent corrosion, we finish the smoothing process.Finally, we set up the coupling system，through testing and analyzing the couplingresult before and after these two kinds of oxidation processes，we verify that the thermaloxidation process plays an important role in the waveguide surface smoothing and optimization. Above all, the double-oxidation process has more advantages on reducing thetransmission loss and improving the quality factor of the waveguide resonators comparedwith the single oxidation process.This paper not only lays the important study foundation for the the achievement ofoptical resonators with lower loss, larger size and higher Q value, but has more researchsignificance and scientific value for the micro-optical devices, optical network, opticalcommunication, especially for the development of nanoscopic optical waveguide gyroscopeand other new devices.