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International Journal of Optics
Volume 2012 (2012), Article ID 173250, 8 pages
Research Article

Nonlinear Coherent Directional Coupler: Coupled Mode Theory and BPM Simulation

Department of Electronics and Communication Engineering, Asansol Engineering College, Asansol, West Bengal 713305, India

Received 7 October 2011; Revised 16 December 2011; Accepted 27 December 2011

Academic Editor: Vittorio M. N. Passaro

Copyright © 2012 Dharmadas Kumbhakar. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


Finite difference beam propagation method is an accurate numerical procedure, used here to explore the switching dynamics of a nonlinear coherent directional coupler. The coupling lengths derived from this simulation are compared with coupled mode theories. BPM results for the critical power follow the trend of the coupled mode theories, but it lies in between two coupled mode theories. Coupled mode theory is sensitive to numerical approximations whereas BPM results practically do not depend on grid size and longitudinal step size. Effect of coupling-region-width and core-width variations on critical power and coupling length is studied using BPM to look at the aspects of optical power-switch design.