Tunable Multi-Channel Circulator Based on Valley Topological Photonic Crystals

We present a magnet-free six-port optical circulator based on two-dimensional valley topological photonic crystals with engineered line defects in chiral unit cells. This design enables topologically protected unidirectional transmission and on-demand channel reconfiguration. Numerical simulations demonstrate operation in the 195.37-196.37 THz (1534-1527 nm) with insertion loss <0.9 dB and isolation >35 dB, maintained consistently across both basic and reconfigured structures. This approach provides a pathway toward highly integrated, reconfigurable photonic devices.