Chaos-assisted unidirectional lasing emission from an ultrahigh-Q whispering gallery microcavity

We reported experimentally a new type of on-chip whispering gallery microcavity which supported both highly unidirectional emission and ultra-high-Q factors exceeding 100 million in near infrared. The highly unidirectional emission results from the chaos-assisted tunneling, which represents a formal analogue to the dynamical tunneling known as a pure quantum mechanical phenomenon. By doping erbium, the unidirectional-emission lasing was observed in 1550 nm band with the threshold as low as 2 µW.