IMPROVED COUPLED-MODE THEORY FOR PARALLEL ELECTRON WAVE-GUIDES

A coupled-mode theory for parallel electron waveguide structures is de veloped and presented. This theory takes the nonorthogonality between the modes belonging to different electron waveguides, which is neglect ed in the first-order theory, into consideration and reflects this fac t by including the modal overlap integral terms in the resultant coupl ed-mode equations. Various numerical examples are presented, using thi s improved theory and the first-order theory, and are compared with th ose of the exact calculations. It is shown that the improved theory ca n give more accurate results than the conventional first-order theory. Therefore, it is very useful for analyzing the quantum field-effect d irectional couplers and similar quantum interference devices.