Highly directional vortex beam emitters based on Archimedean spiral adiabatic waveguides

We demonstrate a highly directional integrated silicon photonic vortex beam emitter based on an Archimedean spiral adiabatic waveguide with angular grating. Various order orbital angular momentum modes can be selectively generated by the emitter at different wavelength and the side-mode superposition ratio is as large as 13.6 dB.