Design And Fabrication Of Interference-type Photonic Integrated Devices

Because of the remarkable development of the optical fiber communication system and network, high performance and low-cost optical devices are indispensable. Integrated optical devices based on the PLC (planar light circuit) technology have already become one of the most attractive choices due to the outstanding advantages. In order to realized flexible and reconfigurable optical networks in the future, further improvements are needed for more cost-effective optical components. For the sake of this goal, this dissertation focuses on the optimal design and fabrication of integrated interferometric-type integrated optical devices.In order to optimize the design of optical waveguide devices, numerical simulation is usually necessary to have better evaluation than the analytical expressions (with some approximations). In this thesis, two numerical tools are used. One is the finite-difference method (FDM) mode solver with a PML (perfectly mathched layer) boundary treatment. The other is a beam propagation method (BPM) for simulating light propagation along the planar ligtwave circuits. By using the FDM solver, the singlemode condition for the SOI (silicon-on-insulator) ridge waveguide with a large cross section is re-examined. The constant c in the formula to determine the singlemode condition is determined, which is very important for the design of SOI ridge waveguide.BPM is used for designing and analyzing the multimode interference (MMI) coupler, which is one of the most important and versatile components. In order to have an optimal design for a 1×N MMI coupler, both the parameter-scanning method and the genetic algorithm are introduced. With the optimal parameters, the MMI coupler has very good performances, e.g., very low non-uniformity and excess loss.Finally, the fabrication processes based on the (planar lightwave circuit) techniques are investigated for developing the integrated optical waveguides & devices. Two typical materials for optical waveguides are considered in this thesis, i.e., SiO2 and SU8. Detailes for the fabrication processes have been discussed, e.g., the thin film deposition with the PECVD machine, the UV lithography for positive as well as negative photoresists, the lift-off process for the metal mask preparation, and ICP (inductive coupled plasm) etching. The optimal parameters for the fabrication processes are very important and useful to develop high performance components.