Electric-field control of the bound states of the window-coupled quantum waveguides

Energy spectrum of two straight quantum waveguides coupled through the opening in their common wall contains, in addition to the continuous part, discrete states with spatially localized orbitals number of which depends on the size a of the connecting window. Here, evolution of these bound levels is calculated when the transverse electric field is applied to the structure. It is shown that for the ground state, which for the voltage-free geometry exists at any nonzero a, the increase of the electric intensity shifts the energy that in the high-field regime approaches fundamental propagation threshold of each waveguide. It is predicted that applied voltage leads to the increase of the window critical widths at which new excited bound states emerge. Physical explanation of this electric-field control of the number of the localized levels is based on the analysis of the propagation thresholds in the opening and waveguides arms. This remarkable electric-field-induced switching of the bound states can be checked by the change of the optical absorption spectrum when the gate voltage is applied. A comparison between the 2D and 3D geometries is presented too.