Modelling And Design Approaches

Abstract

In this chapter, we present an overview of the simulation and design tools useful for silicon photonics component and circuit design. The design methodology for silicon photonic systems is illustrated in Figure 2.1. The order of the material presented in this book follows this illustration from top down. The design of passive silicon photonic components is considered in Part II, Chapters 3–5, while active component design is considered in Part III, Chapters 6–7. Model synthesis is described throughout these sections, and in more detail in Chapter 9, in which we describe optical circuit modelling techniques. Circuit modelling initially is focused on predicting the system behaviour in the presence of external stimulus, namely electrical and optical signals. Once a circuit is designed, the designer uses the schematic to lay out the components in a physical mask layout using a variety of design aids, as described in Chapter 10. This is followed by verification, including manufacturing design rule checking (DRC, DFM), layout versus schematic checking (LVS), test considerations, lithography simulation, and parasitic extraction. The results of the verification are fed back into the circuit simulations to predict the system response including effects due to the physical implementation (e.g. lithography effects, fabrication non-uniformity, temperature, waveguide lengths, and component placement). In this step, the circuit simulation takes into account not only the external stimulus but also the fabrication process (Chapter 11) and environmental variations. The design methodology was presented in Reference [1]. Optical waveguide mode solver An eigenmode solver (or mode solver) solves for optical modes in a cross-section of an arbitrary waveguide geometry (or a 3D geometry) at a particular frequency. A waveguide mode is a transverse field distribution that propagates along the waveguide without changing shape; the solution is time-invariant. An example mode profile is shown in Figure 2.2a. Eigenmode solvers determine time-harmonic solutions to Maxwell's equations in the frequency domain. Since they provide a solution for a single optical frequency, numerous simulations are required to obtain wavelength sweeps needed to study waveguide dispersion.