Coupled-mode theory for cherenkov-type guided-wave terahertz generation via cascaded difference frequency generation

Abstract

A scheme for monochromatic terahertz (THz) generation via cascading enhanced Cherenkov-type difference frequency generation (DFG) in a sandwich-like waveguide is proposed. The novel scheme has the potential to overcome the quantum-defect limit and to provide an efficient output coupling. This process is elucidated by developing a coupled-mode theory and taking into account the pump depletion, waveguide mode properties, and THz output coupling. The effect of cascading enhancement is analyzed by comparing with non-cascaded DFG situation. It is predicted that THz power can be boosted by nearly 8-fold with a 400 MW/cm2 pump in a 40-mm-long Si-LiNbO3-Si waveguide. © 1983-2012 IEEE.