Coherent FIR/THz wave generation and steering via surface-emitting thin film lithium niobate waveguides.

Generating narrowband, continuous wave FIR/THz light via difference frequency generation (DFG) remains challenging due to material absorption and dispersion from optical phonons. The relatively new platform of thin film lithium niobate enables high-confinement nonlinear waveguides, reducing device size and potentially improving efficiency. We simulated surface-emitting DFG from 10 to 100 THz in a thin film lithium niobate waveguide with fixed poling period, demonstrating reasonable efficiency and bandwidth. Furthermore, adjusting wavelength and relative phase in an array of these waveguides enables beam steering along two directions. Continuous wave FIR/THz light can be efficiently generated and steered using these integrated devices.