Organic Synthetic Photonic Systems with Reconfigurable Parity–Time Symmetry Breaking for Tunable Single‐Mode Microlasers

Abstract Synthetic photonic materials exploiting the quantum concept of parity–time (PT) symmetry lead to an emerging photonic paradigm—non‐Hermitian photonics, which is revolutionizing the photonic sciences. The non‐Hermitian photonics dealing with the interplay between gain and loss in PT synthetic photonic material systems offers a versatile platform for advancing microlaser technology. However, current PT‐symmetric microcavity laser systems only manipulate imaginary parts of the refractive indices, suffering from limited laser spectral bandwidth. Here, an organic composite material system is proposed to synthesize reconfigurable PT‐symmetric microcavities with controllable complex refractive indices for realizing tunable single‐mode laser outputs. A grayscale electron‐beam direct‐writing technique is elaborately designed to process laser dye‐doped polymer films in one single step into microdisk cavities with periodic gain and loss distribution, which enables thresholdless PT‐symmetry breaking and single‐mode laser operation. Furthermore, organic photoisomerizable compounds are introduced to reconfigure the PT‐symmetric systems in real‐time by tailoring the real refractive index of the polymer microresonators, allowing for a dynamically and continuously tunable single‐mode laser output. This work fundamentally enhances the PT‐symmetric photonic systems for innovative design of synthetic photonic materials and architectures.