Fig. 1
From: Bound states in the continuum and long-lived electronic resonances in two-tangent loops cavity
(a) The two tangent loops cavity studied in this work. The cavity made out of two tangent loops of lengths \(L_1\) and \(L_2\). When closing the guide \(L_1\) at space point 0, one connects to it the 0 end of the guide of length \(L_2\) (figure a). Finally two semi-infinite leads are connected to the space point 0 (figure b). The space point 0 is the point of connection of the two semi-infinite leads with the two loops, \(L_1\) and \(L_2\), constituting the cavity. This is why we call it interface point. The interface space for this cavity structure is the point 0. This interface space is written shortly as: \(M=\left\{ 0\right\}\). Let us also mention that the Kirchoff-Neumann boundary condition is used at the interface point 0. (c) The two loops cavity structure is attached only to one port from one side.
