Extended Data Fig. 1: Design and fabrication of the topological microring array.
From: Co-propagating photonic topological interface states with hybridized pseudo-spins
a, Design schematic of the microring array with a pseudo-spin-flipping interface. Adjacent site rings (black) within each domain are coupled via a link ring (green), with gap \({d}_{1}\) controlling the coupling strength. To implement a synthetic gauge phase of \(\varphi =2\pi / 3\), the link rings that connects the site rings in y-direction are vertically shifted in an arithmetic sequence with a displacement of \(\Delta y={\lambda }_{0} / (6{n}_{{\rm{eff}}})\), where \({\lambda }_{0}\) is the free-space wavelength and neff is the effective index of the guided mode inside the ring resonators. The site rings along the interface are coupled via a pair of link rings (purple), with gap \({d}_{2}\) (between the link rings) and \({d}_{3}\) (between the link rings and the site rings) jointly controlling the pseudo-spin–flipping coupling strength. b, Fabrication flow of the topological microring array. HSQ: hydrogen silsesquioxane; ICP: inductively coupled plasma; PECVD: plasma-enhanced chemical vapor deposition.
