Ultrafast control of fractional orbital angular momentum of microlaser emissions
Zhang, Zhifeng; Zhao, Haoqi ; Gomes Pires, Danilo; Qiao, Xingdu ; Gao, Zihe; Jornet Josep M.; Longhi, Stefano; Litchinitser, Natalia M.; Feng, Liang
Light: Science & Applications 9, 179 (1-9) (2020)
On-chip integrated laser sources of structured light carrying fractional orbital angular momentum (FOAM) are highly
desirable for the forefront development of optical communication and quantum information–processing technologies.
While integrated vortex beam generators have been previously demonstrated in different optical settings, ultrafast
control and sweep of FOAM light with low-power control, suitable for high-speed optical communication and
computing, remains challenging. Here we demonstrate fast control of the FOAM from a vortex semiconductor
microlaser based on fast transient mixing of integer laser vorticities induced by a control pulse. A continuous FOAM
sweep between charge 0 and charge +2 is demonstrated in a 100 ps time window, with the ultimate speed limit being
established by the carrier recombination time in the gain medium. Our results provide a new route to generating vortex
microlasers carrying FOAM that are switchable at GHz frequencies by an ultrafast control pulse.