Iterative TD-BPM for modeling ultrashort pulse in z-variant optical structures

In this work, the Iterative Time Domain Beam Propagation Method (TD-BPM) has been implemented in the propagation of femtosecond pulsed beam inside two dimensional Y-junction. Being an implicit technique, it is free from Courant-Friedrichs-Lewy (CFL) stability criteria. Moreover, the mesh grid (Δx) and the propagation step (Δz) sizes are much more relaxed compared to the explicit one, such as the Finite Difference Time Domain (FDTD)technique. In order to verify the result, the FDTD has been implemented on the same problem and the result has been compared. The comparison shows a good agreement between the techniques.