Theoretical research on terahertz wave generation from planar waveguide by optimized cascaded difference frequency generation

A novel scheme for high-efficiency terahertz (THz) wave generation based on optimized cascaded difference frequency generation (OCDFG) with planar waveguide is presented. The phase mismatches of each-order cascaded difference frequency generation (CDFG) are modulated by changing the thickness of the waveguide, resulting in a decrement of phase mismatches in cascaded Stokes processes and an increment of phase mismatches in cascaded anti-Stokes processes simultaneously. The modulated phase mismatches enhance the cascaded Stokes processes and suppress the cascaded anti-Stokes processes simultaneously, yielding energy conversion efficiencies over 25% from optical wave to THz wave at 100 K.