Integrated Compact Optical Vortex Beam Emitters

A Twist of Light The angular momentum of photons can be used to encode and transmit information. Cai et al. (p. 363 ) developed a method for generating and emitting controllable orbital angular momentum states of light from a reconfigurable and scalable silicon photonic chip. Using micro-ring resonators embedded with angular gratings allowed the imprinting of optical angular momentum on the light propagating in the whispering gallery modes of the resonator. The method may enable large-scale integration of optical vortex emitters on complementary metal-oxide–semiconductor-compatible silicon chips.