Thermo-optic simulations of silicon nitride / polymer hybrid waveguides

Abstract

ABSTRACT We perform the thermal and optical simulations of silicon nitride / polymer hybrid waveguides with different heating schemes by finite element method. Both the top and buried microheaters are adopted to realize tuning function by the thermo-optic effect. We find the buried microheater is more energy-efficient than the top microheater in creating a uniformed temperature environment in the waveguide region. On the other hand, the top electrode tends to create a strong temperature gradient through the waveguide, which in turn distorts the optical mode. This distortion, however, is different for TE and TM modes. This thermally induced birefringence effect is thoroughly investigated in this paper. Keywords: Silicon nitride waveguide, polymer, microheater, bire fringence, thermal simulation, thermo-optic effect 1. INTRODUCTION Optical integration has attracted much attention worldwide, because of the compact size, cost effectiveness, improved functionalities, and so on. Planar waveguide technologies, including SOI (silicon on insulator), silica-on-silicon, III-V semiconductors, lithium niobate, and polymers, have been extensively investigated due to their potentials of providing a platform for the optical integration. Polymer materials present several advantages, such as low-cost production, fast prototyping, and versatility to incorporate other dielectric and metal materials. In addition, polymers possess both high thermo-optic coefficient and low thermal conductivity [1], wh ich makes them ideal to realize thermally tunable devices, such as variable optical attenuators [2], digital optical switches [3, 4], tunable filters [5], and so on. The thermo-optic coefficient (TOC) of polymer materials is on the order of -1.0 to -3.0 ×10