MODES OF PERIODICALLY SEGMENTED WAVE-GUIDES

Modal properties of periodically segmented waveguides (PSW) are analyz ed by using the beam-propagation method and the coupled-mode theory. T he modal effective indices in a PSW are shown to be equal to those of a continuous waveguide with an averaged DELTAn. As a result, guided mo des spread out, particularly those that are not strongly guided. The r adiation loss is shown to oscillate with most of the waveguide paramet ers. In practical terms, this loss can be made negligible even for lon g periods. The results can be applied to the design of novel waveguide devices such as two-dimensional mode tapers and frequency-selective c ouplers.