![]() ![]() In which way do reflections create a problem? Reflections are also solutions to Maxwell’s equations. The problem we face is the reflection from a material interface a lens surface, for example. We frequently want to solve optical systems that include inhomogeneous domains. So, if we always simulate homogeneous domains and solve for a solution that has slowly varying envelopes, then we are done with this interface. Using this method, you don’t need a lot of mesh elements. You can use this interface if the solution’s envelopes are slowly varying. Lens Simulations with the Beam Envelopes InterfaceĬompared to conventional Maxwell solvers, the Beam Envelopes interface in the COMSOL® software doesn’t have this difficulty, because the fast oscillation part is factored out in the formulation. The BPM doesn’t have this problem, because the field solution literally propagates (or jumps) from one plane to another by using a certain propagation law, in which you don’t need a mesh between the planes. Then, it becomes problematic when you want to simulate a large object, like standard optical lenses. For this reason, we need a mesh throughout the domain, and the mesh elements need to resolve the wavelength. In the conventional Maxwell solver, all points within the computational domain contribute when running the simulation. Interference patterns due to surface reflections.However, when it comes to optics simulation, there is a problem with the “conventional” Maxwell solver: It requires a fine mesh and lot of memory to solve: The full-wave Maxwell solver looks like the greatest method. The BPM typically includes various approximations in the formulation, such as the Fraunhofer approximation (i.e., Fourier transformation) and the Fresnel diffraction formula. The full-wave Maxwell solver literally solves Maxwell’s equations, so it’s rigorous and there is theoretically no model approximation. Ray tracing is an approximation where the wavelength is negligible compared to the object size therefore, it doesn’t deal with diffraction. ![]() Wave optics: BPM (Fraunhofer, Fresnel, others) Wave optics: full-wave Maxwell (conventional) Each method has certain limitations, outlined below: In wave optics, we consider two types of methods: a full-wave Maxwell method and a beam propagation method (BPM). If you want to simulate the diffraction effect (even simply focusing a beam introduces diffraction), wave optics is needed. There are two main categories of methods to simulate optics: Introduction to the Optics Simulation Methods In this blog post, we demonstrate how the Wave Optics Module, an add-on to the COMSOL Multiphysics® software, can be used to perform lens simulations based on Maxwell’s equations. Performing lens simulations in wave optics is generally difficult, because it requires a lot of mesh elements. ![]()
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