Planar Photonic Circuits can perform many useful functions in optical communications systems, such as wavelength division multilplexing (WDM), optical channel add/drop, fibre/waveguide coupling, and amplifier gain equalization. They perform these functions by the interaction of the device structure with the light inside them. There are very effective and proven numerical methods available for modelling this interaction, such as the Beam Propagation Method (BPM), the Finite Difference Time Domain (FDTD) method, and coupled mode theory (CMT). However, these methods work on a microscopic level (typically the smallest distance is about 0.1 microns), but photonic circuits, on the other hand, can occupy an entire wafer (scale: 10 cm). The analysis must span 5 or more orders of magnitude in the change in scale. The successful analysis needs to combine the basic microscopic techniques with an approach at a more abstract, or system, level. It is interesting that software designed for the analysis of optical communication systems can be applied to planar photonic circuits. This paper shows an example of a practical photonic circuit, a lattice filter, that cannot be analysed by BPM alone. It will be demonstrated that when used with a system level analysis, the whole device can be simulated.
We present the state of the art for commercial design and simulation software in the 'front end' of photonic circuit design. One recent advance is to extend the flexibility of the software by using more than one numerical technique on the same optical circuit. There are a number of popular and proven techniques for analysis of photonic devices. Examples of these techniques include the Beam Propagation Method (BPM), the Coupled Mode Theory (CMT), and the Finite Difference Time Domain (FDTD) method. For larger photonic circuits, it may not be practical to analyze the whole circuit by any one of these methods alone, but often some smaller part of the circuit lends itself to at least one of these standard techniques. Later the whole problem can be analyzed on a unified platform. This kind of approach can enable analysis for cases that would otherwise be cumbersome, or even impossible. We demonstrate solutions for more complex structures ranging from the sub-component layout, through the entire device characterization, to the mask layout and its editing. We also present recent advances in the above well established techniques. This includes the analysis of nano-particles, metals, and non-linear materials by FDTD, photonic crystal design and analysis, and improved models for high concentration Er/Yb co-doped glass waveguide amplifiers.
In the present paper we review the state of the art of two complementary propagation techniques with applications for integrated optics device modeling: the Finite-Difference Time-Domain and the Beam Propagation Method. In both cases we focus on their main features such as the types of propagation schemes and the material effects that can be modeled. In addition, we also consider a 2D mode solver based on a complex root finding procedure - a representative mode solving technique that is of significant interest for design and modeling of leaky mode based devices. Each of the methods is illustrated with appropriate simulation examples of devices and waveguide structures being of current research interest: photonic band gap structures, waveguide gratings, ARROW waveguides etc. The selected examples show the power of the methods as well as the consistency and the complementarity of their results when applied together.