Numerical and experimental investigation of 2×2 optical switch in silica-on-silicon

In this paper, we designed a 2×2 Mach-Zehnder (MZI) thermooptic switch based on multimode interference (MMI) couplers in silica-on-silicon. Issues concerning the influence of a number of design parameters for a 2×2 multimode interference couplers are discussed. The beam-propagation method (BPM) was used to demonstrate the feasibility of the proposed design of compact MMI coupler. Instead of standard fabrication process, we utilized a different lithography metrics to define the desired waveguide patterns. P-doped silica films were deposited on Si substrates using a plasma-enhanced chemical vapor deposition system. Optical properties of the films including refractive index, thickness and uniformity were examined by a prism coupler of optical interference method. We successfully used reactive ion etching (RIE) to fabricate a low loss straight waveguide with smooth sidewall. For silica waveguides, the thermo-optic effect is used to tune the local refractive index of the guiding layer. A resistive material such as aluminum was used as heating element. The silica-on-silicon technology with surface micromachining revealed an optimal design of a low power compact thermooptic switch. This paper would summarize the development of this novel process for the realizing of the designed optical switch and its applicability in fabricating planar waveguide circuit.