Integrated vortex beam emitter in the THz frequency range: Design and simulation

Abstract

Compact vortex beam emitters have emerged as new light sources for novel applications in areas including spectroscopy, particle manipulation, and communications. Reported devices depend on linear optical phenomena and emit light in the near-infrared (IR) regime. Here, we propose and numerically evaluate a nonlinear vortex beam emitter that functions in the THz regime. The design utilizes a LiNbO3 microring, a Si microdisk, and an Au second-order top grating to convert waveguide-coupled IR light into a freely propagating THz beam via a difference-frequency generation. The output beam carries a topological charge that is tunable with input wavelengths. Three devices are evaluated in a test frequency range from 9 THz to 13.5 THz, and the topological charge can change from -2 to 4. A frequency shift accompanies the change in the topological charge, and its magnitude depends on the planar dimensions of the emitter.