A theoretical investigation on the quantum field effect directional coupler

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Abstract
A theoretical investigation on the quantum field effect directional coupler is presented. The behavior of electrons in the device is studied by solving the Schrödinger equation directly. The complete transfer effect is revealed to be an intrinsic property of the parity symmetry of the system. Transfer length is precisely calculated by using the transfer matrix method. Two model transverse confinements have been used in the calculation. One is a symmetric double rectangular well; and the other is a symmetric double finite‐parabolic potential. Conductance of the device is investigated by applying the Landauer formula. Conductance oscillations with Fermi energy and barrier height are obtained. One method of determining the transfer length from the curve of conductance vs barrier height is proposed. Special attention is paid to the multimodedness of the device. Correlation among the different modes is demonstrated to reduce the transfer effect of the device. Reflection at the interfaces between uncoupled and coupled waveguides is proved to be negligible.