All-Optical Modulation of Microcavity Emission by Parity-Time Symmetry

Integration of microcavity-based coherent light sources and waveguides is of central importance for building optical networks and photonic circuits. However, such combined devices face severe challenges in distributing the generated signals to designed ends despite that the significant advances are accomplished in emission modulation and controlling. Herein, dynamically all-optical control of the outputs from the microcavity by employing parity-time (PT) symmetry is demonstrated. By exploiting the interplay between gain and loss in a waveguide-connected microsquare cavity, the mode field distributions can be strongly modified when the non-Hermitian system enters PT-symmetry breaking phase. Numerical calculations and the corresponding Husimi projections unambiguously show the PT-symmetry-induced mode localization and output redistributions in microsquare cavity. Notably, the intensity ratios of the lights collected by the two channels can be directly tuned over two orders of magnitude with the increase of pumping strength. These findings will be essential for understanding the fundamentals of non-Hermitian optics and advancing the application potentials of microcavity system in integrated photonics.