  The exploration of quantum-inspired symmetries in optical systems has spawned
promising physics and provided fertile ground for developing devices exhibiting
exotic functionalities. Founded on the anti-parity-time (APT) symmetry that is
enabled by both spatial and temporal interplay between gain and loss, we
demonstrate theoretically and numerically bi-color lasing in a single
micro-ring resonator with spatiotemporal modulation along its azimuthal
direction. In contrast to conventional multi-mode lasers that have
mixed-frequency output, our laser exhibits stable, demultiplexed, tunable
bi-color emission at different output ports. Our APT-symmetry-based laser may
point out a new route for realizing compact on-chip coherent multi-color light
sources.
