Diverse and controllable excitations of coupled modes of unidirectional air waveguides

Abstract. In order to obtain the waveguide of multiple functionalities, we design a coupled system of two unidirectional air waveguides and find it is a system of multiple modes through band calculations. Through numerical simulations, we also find that the mode excitation is dependent on the position of the source. With the same frequency the line source can excite either the even mode or the odd modes in one single waveguide or two waveguide just by changing the positions of the source. Such a system provides us the way to control the excitation of mode and obtain the waveguide modes with special applications.