Research On Low-Driving-Power Thermo-Optical Switch Utilizing Total Internal Reflection

Optical switch has become one of the key technologies in photonics. Optical switch device is not only the core component in optical add-drop multiplexer (OADM) and optical cross-connect (OXC) which are necessary in dense wavelength division multiplexing (DWDM) network nowadays, but also the key module in all-optical network (AON). As for optical sensing, optical computer and other fields, optical switch is also widely applied.Various design principles can be used to fabricate optical switch, and lots of different kinds of materials can also be available. While in the past decades, polymer material had drawn wide attention due to its low price, simple process but excellent properties. On the other hand, the structure of total internal reflection (TIR) also became a very popular design which has the advantage of compact size and digital response to driving signal. Lots of thermo-optical switch designs using polymer materials had been proposed, while some of them had to face the fact that polymer materials often lead to high power consumption. In this dissertation, a hybrid optical switch configuration using both silicon oxynitride (SiON) and polymer is proposed and demonstrated. The proposed switch consists of an X-junction formed by two optical waveguides, and in the middle of the X-junction, a trench is designed to fill polymer material. With such a structure, the power consumption can be reduced because of the opposite thermo-optical effect of SiON and polymer. In addition, the broadened waveguide structure will be used to reduce the loss.Main contents are summarized as follows:The structure and principle of the proposed optical switch are presented at first, followed by the detail of the materials. Rectangular waveguides are designed by using Marcatili method, while reflectance and transmittance are obtained by TIR and homogeneous dielectric film approach. Key parameters are decided based on the calculation, and finally the trench width of 2.5 urn and the angle between two branches of about 35° are determined to fit the proper structure.Based on the structure of optical switch, mask is designed and custom-made. After studying process of photolithography, sputtering and inductively coupled plasma (ICP) etching, the samples of thermo-optical switch have been fabricated with optimal parameters and process.The performances of the fabricated thermo-optical switches are characterized by using high precision optical measurement platform. After optimization and improvement, the switch with driving power of 59 mW, rise time of 1.8 ms and fall time of 1.0 ms is obtained. Then the cause of high switch power is discussed, and some improving measures and proposals are put forward.