Asymmetric optical mode conversion and transmission by breaking PT-symmetry on silicon photonic circuits

► We have designed a silicon-based optical waveguide with complex optical potential. ► In the waveguide, we observe a novel phenomenon of spontaneous PT symmetry breaking. ► It shows unidirectional mode conversion and one-way amplification of transmission. ► We have shown usual PT principles and rigorous theoretical analysis and discussion. ► This result may pave the way for the more exciting on-chip photonic devices.