A novel wide-angle beam propagation method based on the spectral collocation scheme for computing titled waveguides

A multidomain spectral collocation beam propagation method that uses an oblique coordinate transformation is proposed for analyzing a beam propagating in dielectric optical waveguides. Relying on the high accuracy of spectral collocation scheme in transverse discretization, the proposed method achieves extremely small power loss (<10^-4, for the tilt angle of a tilted waveguide up to 20°) but considerably save the computational resources. Furthermore, by means of introducing the oblique coordinate system, not only is a significant difficulty arising from staircased approximation of refractive index completely avoided, but the implementation of the present scheme becomes easier. To validate the effectiveness, numerical results for propagating beam in a tilted step-index optical waveguide are compared with other beam propagation algorithms.