Fig. 1. Schematic of the graphene/AlGaAs surface plasmon waveguide.

Fig. 2. (a) Real and (b) imaginary refractive index of graphene versus the Fermi energy level for 2, 4, 6, and 8 THz, respectively.

Fig. 3. Electric field profiles of (a) TM single mode at 6 THz, (b) TE fundamental mode at pump wavelength λp=1.53  μm, and (c) TM fundamental mode at signal wavelength λs=1.5783  μm. (d) Effective interaction area Aeff as a function of THz wave frequency.

Fig. 4. (a) Phase mismatch Δk as a function of Fermi energy level for 5.8, 5.9, 6.0, and 6.1 THz generation. (b) Phase-matching THz frequency as a function of Fermi energy level.

Fig. 5. (a) Contour image of power-normalized conversion efficiency versus waveguide length for different THz wave frequencies. (b) THz wave power versus THz frequency for waveguide length 500 μm and 2500 μm with Pp=100  W and Ps=1  W.

Fig. 6. Optical pulse evolutions along the waveguide with 30 ps pulse input pump with peak power 100 W and 1 W CW input signal: (a) pump wave power, (b) signal wave power, and (c) THz wave power.