Analysis of "quasi-modes" in periodic segmented waveguides

A three-dimensional (3-D) explicit finite difference beam propagation method (3-D EFD-BPM) has been used to study the modal characteristics and losses of periodic segmented waveguides (PSWs). Results for the variation of the mode width and depth, as a function of the duty-cycle and period, are presented and compared with those obtained using the equivalent continuous waveguide model at a wavelength of 1.55 /spl mu/m. The radiation losses associated with the modulation of the refractive index are studied and we show that a 3-D representation of a PSW is necessary to evaluate the radiation loss.