2D modeling of silicon optical PN phase shifter.

Abstract

In this paper, a 2D model of a silicon lateral PN optical phase shifter is presented, which can be used for multiple-parameter study and optimization of device performance without the need for any commercial numerical tools. The model shows good agreement with technology computer-aided design (TCAD) simulation and can be used to calculate the phase shift, absorption loss, modulation efficiency, and insertion loss of the phase shifter. Multiple-parameter study includes the waveguide dimensions, operating wavelength, cladding material, doping concentrations, junction offset, and applied voltage. The model employs the effective index method to determine the mode properties and construct the 2D mode field. The PN diode is modeled by taking into account the fringing electric field at the core-cladding interface, which results in a wider depletion region near the interface. Multiple-loss components are discussed, and the scattering loss and free-carrier absorption are modeled using Payne-Lacey and Soref models, respectively. The model uses 2D modal overlap with 2D carrier distribution across the waveguide to calculate the phase shifter performance metrics. The algorithm used to model the 2D nature of the PN diode depletion region is presented in detail and uses mathematical and analytical formulas instead of numerical methods, making the model faster and easy to implement, with accuracy on par with commercial tools.