Formation and observation of chiral resonances in optical microcavities

Chirality is a kind of important phenomenon around the exceptional point. The chirality of long-lived resonance has been theoretical studied and has shown promising potentials in nanoparticle sensing and rotation sensing. However, the researches on chirality are mostly limited in theoretical studies. The experimental demonstrations are quire challenging, especially in low refractive index microcavities. Here we demonstrate the formation and the observation of relatively long-lived chiral resonances in polymer microdisks. By placing a spiral microdisk in proximity, we find that chirality can be achieved in relatively long-lived resonances of conventional microdisks with mirror-reflection symmetry. The detail numerical calculations show that the chirality is mostly caused by the asymmetrical scattering of leakages from initial microdisk. Most importantly, we find that the directional emissions in far field pattern and the chirality are strongly correlated with each other, providing a simple measure to determine the chirality experimentally. Based on the theoretical studies, we have fabricated polymer microdisks and studied their lasing actions. Asymmetrically directional laser emissions have been successfully observed in the far field, matching the theoretical predictions well. We believe that our finding will be important for both the fundamental researches on the chirality and the applications in optical sensors.