Semiconductor lasers: Monolithic terahertz source

Twisted relativistic light pulses with a strong torque and an ultrahigh orbital angular momentum density can in principle be created by shining light pulses onto a specially design thin metal foil, report scientists in China. Theoretical analysis and simulations by Yin Shi and co-workers at the Shanghai Institute of Optics and Fine Mechanics predict that when intense pulses with planar wavefronts strike a metal foil having a spiral of fan blades of stepped height, the pulses obtain a helical wavefront on reflection. The relativistic laser beam exerts a strong torque on the foil, which is transferred to the reflected light, resulting in a twisted light beam. This proposal both sheds light on the dynamics of high-intensity laser–plasma interactions and paves the way to revealing new, exciting applications using twisted, intense laser pulses. MM