Asymmetric nonlinear-mode-conversion in an optical waveguide with PT symmetry

Asymmetric mode transformation in waveguide is of great significance for on-chip integrated devices with one-way effect, while it challenging to achieve asymmetric nonlinear-mode-conversion (NMC) due the limitations imposed by phase-matching. In this work, we theoretically proposed a new scheme realizing NMC combining frequency-doubling process and periodic PT symmetric modulation an optical waveguide. By engineering momentum from modulation, have demonstrated unidirectional conversion pump second harmonic desired guided modes. Our findings offer opportunities manipulating nonlinear fields symmetry, which could further boost more exploration on assisted non-Hermitian optics.