Exceptional points in microresonator Brillouin laser systems*

We theoretically proposed and experimentally demonstrated the existence of exceptional points (EPs) in an on-chip microresonator Brillouin laser system. The coalescence of the eigenfrequencies as well as the eigenmodes is presented. When the laser system is operating near the EP, the boosted rotational sensitivity is confirmed, which enables on-chip optical gyroscopes with unprecedented sensitivity. Moreover, EPs also emerge below the lasing threshold, and the coherent perfect absorption (CPA) can be realized by tuning the pump power. EPs in on-chip microresonator Brillouin systems have applications in precise sensing and optical information manipulating.