Photonics is a difficult subject because it involves electromagnetism that is basically an invisible and unintuitive world to many students. Yet this is a promising and thriving technical field where many jobs are being created.

Computer simulation of light propagation in medium has become an important part in the design of optical waveguides, photonic circuits and optical fiber communication units. Commercial tools such as those developed by Optiwave have been widely used in industry. These tools and methods may also be very useful in helping students develop intuition ans sense about photonics.

Theoretical photonics is largely based on the numerical solution of the Maxwell equation, which governs light propagation. Solving the Maxwell equation for different system configurations is by no mean a trivial task. Many approximations have been developed. Each is good at solving a particular type of problem. Most of them are based on either the finite element method (FEM) or the finite difference method (FDM). Among them, the beam propagation method (BPM) is one that was specifically developed to simulate light propagation in waveguides. It gives reasonably accurate results that can provide useful guidance to designing optimal photonic circuits.

BPM seems to be an attractive candidate of teaching tool in that it can be used to build salient (that is, interactive and dynamic) simulations that show h0w things work in photonic devices. A playful environment that allows students to build circuits and run simulations to see how light travels through them may be very instructive and attractive to students.

The following pictures show a BPM 2D simulation of a photonic parallel circuit (many real engineering problems can be reduced to 2D based on the effective index method). Note that there are some loss due to the twist of the two branches where they split and join.