It is shown that asymmetry severely decreases the ability to transfer current from one waveguide to the other, except in the case of effective‐mass asymmetry where it causes an energy‐dependent transfer efficiency. The influence of various parameters and structure asymmetries on the directional coupling process is investigated. As determined by supermode simulations, coupled‐mode analyses give inaccurate directional‐coupling transfer lengths when the coupling is strong or the electron energy is low. It is shown that the eigenmodes of electron waveguides having spatially varying effective mass satisfy an orthogonality relation that involves the effective‐mass profile. A transfer‐matrix technique is used to calculate the eigenmodes of multiple‐layer structures having arbitrary potential‐energy/effective‐mass profiles that form the coupled electron waveguides. Electron wave directional coupling between parallel semiconductor electron waveguides is analyzed by calculating the supermode (superposition of eigenmodes) of the complete structure.
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