Quantum symmetry, especially parity-time (PT) symmetry, has been widely explored in nanostructures and waveguides for developing a new generation of photonic devices, including lasers. However, the introduction of static gain and loss components into these systems prevents the development beyond monochromatic lasing operation. Founded on another quantum symmetry, i.e., anti-parity–time (APT) symmetry that is enabled by both spatial and temporal interplay between gain and loss, for the first time, our group demonstrated a micro-ring system that can be switched between an amplifying nonreciprocal isolator and a bi-color laser by tuning modulation depth or modulation frequency. Specifically, this bi-color single-mode laser exhibits stable, demultiplexed, tunable emission at different output ports for different frequencies. Our APT-symmetry-based laser may point out a new route for realizing compact on-chip coherent multi-color light sources.
Reference: Y. Duan, X. Zhang, Y. Ding, and X. Ni, “Single-cavity bi-color laser enabled by optical anti-parity-time symmetry,” Photon. Res. 9, 1280-1288 (2021). https://doi.org/10.1364/PRJ.417296