Fig. 6: Experimental design for ZIM-induced BIC in a metallic rectangular waveguide system.
From: Geometry symmetry-free and higher-order optical bound states in the continuum
a Schematic diagram of a metallic rectangular waveguide system with ZIM. The upper parallel metallic plate is hidden to show the internal structure clearly. b Numerically calculated transmission spectrum |S21| of the designed waveguide system with ZIM. The grey region shows the parameter region of \({\varepsilon }_{{\rm{eff}}}\approx {\mu }_{{\rm{eff}}}\approx 0\). The inset shows the magnetic field in the middle plane (z = H/2) at the resonant transmission. c Schematic diagram of the metallic rectangular waveguide system for observing BIC, where two dielectric rods (aluminium oxide) are added in the designed waveguide system with ZIM. d Transmission spectrum |S21| for the aluminium oxide rods with different \(\alpha\). The red solid and yellow dashed curves denote the two different distributions of aluminium oxide rods. The insets show the corresponding magnetic field patterns in the waveguide junction (square area) with doped rods. Simulation parameters of \({R}_{1}\) and \({R}_{2}\): \(\alpha =6.4\times {10}^{-3}\) (\({R}_{1}=16.176\,{\rm{mm}}\) and \({R}_{2}=16.280\,{\rm{mm}}\)), \(\alpha =4.0\times {10}^{-3}\) (\({R}_{1}=16.195\,{\rm{mm}}\) and \({R}_{2}=16.260\,{\rm{mm}}\)), \(\alpha =1.5\times {10}^{-3}\) (\({R}_{1}=16.215\,{\rm{mm}}\) and \({R}_{2}=16.240\,{\rm{mm}}\)), \(\alpha =0\) (\({R}_{1}={R}_{2}=16.227\,{\rm{mm}}\)). In all simulations, the metals are the perfect electric conductor (PEC) and the material parameters are \({\varepsilon }_{t}=2\), \({\varepsilon }_{{\rm{Si}}}=11.7\), \({\varepsilon }_{{\rm{d}}}=9\).
