A tunable silicon-on-insulator valley Hall photonic crystal at telecommunication wavelengths.

Silicon-on-insulator (SOI) combined with topological photonics provides on-chip integrated photonic devices CMOS-compatibility and backscattering-suppression. Here we propose a tunable SOI-based valley Hall topological insulator with two nonequivalent air holes to break inversion symmetry. Due to free-carrier excitation, the real and imaginary parts of the refractive index are modified to cause a blue-shift of bandgap and a reduction of transmittance, respectively. Based on this mechanism, we design a tunable all-optical switch with the merits of high transmittance contrast (about 23) and polarization-resolved characteristics simultaneously. Our proposed approach has potential in broadband tunable integrated photonic devices at telecommunication wavelengths. [ABSTRACT FROM AUTHOR]