Abstract
A simple and efficient approach is utilized to extract the propagation constants of any guided structures and their sensitivities using FDTD. Using our approach, the propagation constants of all the guided modes are obtained at all the desired frequencies using only one simulation. It is also capable of extracting the sensitivities of the propagation constants with respect to all the design parameters, regardless of their number, without any additional simulation. Results show good agreement between our approach and existing analytical approaches.