Higher order mode conversion induced by discontinuities in waveguides

In this paper, we provide a theoretical prediction about the likelihood of producing high-order modes using, as far as we know, the simplest mode converter. The mode converter is a simple discontinuous waveguide for which reflection and transmission have recently been reported. As a result of the scattering of the fundamental guided mode (TE0), we have found that the high-order mode excitation is highly dependent on the position of the discontinuity. On the one hand, we discovered that in the presence of a discontinuity in the propagation direction, only even modes (TE0 and TE2) are excited, skipping the odd mode (TE1). When a lateral shift is considered, however, both even and odd higher-order modes (TE1 and TE2) are generated. Furthermore, after some lateral shifting, we found that only the pure TE2 mode is propagated.