Topological photonic crystal biosensor with valley edge modes based on a silicon-on-insulator slab

In the development of integrated sensing, how to reduce losses and improve robustness has always been one of the key problems to be solved. The topological photonic crystal structure based on the quantum Hall effect has gradually attracted the attention of researchers due to its unique immune defect performance and anti-scattering performance. Here, we have successfully applied the valley photonic crystal structures to topologically manipulate the light within the band gap of 252 THz-317 THz in a silicon-on-insulator platform. We experimentally demonstrated that satisfactory transmission performance can be obtained using the valley-dependent topological edge states below light cone, even if there are structure defects such as lattice missing and lattice mistake near the interface between two kinds VPCs. Based on the features of topological protection, a triangular cavity consisting of three 10×a-length sides is proposed, and the Q factor value reaches 1.83×10⁵ with little influence from defects. Finally, based on drying etching technology, a biosensor with cavity-coupled waveguide structure was prepared, and the RI sensitivity was 1228 nm/RIU.