Highly efficient terahertz generation from periodically poled lithium niobate

Terahertz (THz) generation from periodically poled lithium niobate with a quasi-phase-matching scheme based on cascaded difference frequency generation (DFG) processes is theoretically analyzed. The cascaded Stokes interaction processes and the cascaded anti-Stokes interaction processes are investigated from coupled wave equations. THz intensities and quantum conversion efficiencies are calculated. Compared with non-cascading DFG processes, THz intensities from 15-order cascading DFG processes are increased to 7.7. The quantum conversion efficiency of 390.85% in cascaded processes can be realized, which exceeds the Manley–Rowe limit.