ITERATIVE FINITE-DIFFERENCE BEAM-PROPAGATION METHOD ANALYSIS OF NONLINEAR-OPTICAL WAVE-GUIDE EXCITATION PROBLEM

The beam propagation method (BPM), used widely for analyzing optical w aveguides and optical circuits, is also being applied to devices that include nonlinear materials. However, in the-analysis of nonlinear opt ical devices using the conventional BPM, in many cases it is assumed t hat the field intensity distribution does not change within the step l ength in propagation direction. Therefore, for accurate calculation, t he step size in the propagation direction must be extremely small, whi ch results in long calculation times. Therefore, this paper proposes a nd formulates a numerical method where the solution is forced to conve rge by the iterative calculation of a difference equation over each pr opagation Step of the Crank-Nicolson BPM method. Using this method, fi rst, we analyzed the case where the fundamental TE mode propagates in the dielectric slab waveguide that has;a Kerr-like nonlinear; cladding . By calculating the emission angle of the optical beam into the cladd ing, tile present method is compared with the conventional method. Aft er it is demonstrated that this present method is effective, the depen dency of the optical beam emission angle for the incident power is sho wn. Furthermore, the effect of the beamwidth on the excitation is anal yzed in the case where a nonlinear stationary wave is excited by a Gau ssian beam and the interesting results are proved.