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.

携带分数轨道角动量（FOAM）的结构化光的片上集成激光源对于光通信和量子信息处理技术的最前沿发展是非常需要的。尽管先前已经在不同的光学设置中演示了集成涡旋光束发生器，但是超低速控制和低功率控制的FOAM光扫描仍然适用于高速光通信和计算，但仍然具有挑战性。在这里，我们展示了基于控制脉冲引起的整数激光涡流的快速瞬态混合，可以快速控制涡流半导体微激光器对FOAM的控制。在100 ps的时间窗口中演示了电荷0和电荷+2之间的连续FOAM扫描，最终速度极限由增益介质中的载流子复合时间确定。