Highly Unidirectional Emission and Ultralow-Threshold Lasing from On-Chip Ultrahigh-Q Microcavities



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Ultrahigh-Q optical whispering gallery microcavities are promising platforms for fundamental studies and applied photonics. A new type of on-chip microcavity is experimentally realized, which supports both highly unidirectional emission and ultra-high-Q factors exceeding 100 million in near infrared. By doping erbium, the unidirectional-emission lasing is observed in 1550 nm band with the threshold as low as 2 μW.