Fig. 2
Panels (a) and (b) show the band structures of PhC1 and PhC2 for the normal incidence, respectively, with the Zak phases indicated for each individual band. The cyan and orange strips correspond to gaps with \(\:{\upzeta\:}<0\) and \(\:{\upzeta\:}>0\), respectively. (c) The transmission spectrum of the proposed PhC1|silicon layer|PhC2 heterostructure with 6-unit cells for each photonic crystal is presented. The existence of a TIS at \(\:\text{d}/{\uplambda\:}=0.4495,\) corresponding to a wavelength of 1540 nm, is clearly observed within the shared second bandgap displayed in this panel. The vertical axes represent the normalized frequency of light. In panels (a) and (b), the horizontal axes correspond to the normalized Bloch wavevector, while in panel (c) the horizontal axis indicates the transmission of the structure.
