Difference frequency generation of widely tunable terahertz waves in 4H-SiC

Abstract

High energy and widely tunable terahertz (THz) generation was demonstrated theoretically based on a semiconductor material 4H-SiC via difference frequency generation (DFG) process. Compared with the conventional THz nonlinear optical (NLO) crystals, 4H-SiC has the main advantages of extremely high optical damage threshold and wide optical transparent range, which implies the potential THz generation with high output energy and broadband tunability. Based on the basic NLO theories, the phase-matching (PM) characteristics, effective nonlinear coefficients, walk-off angles, and PM tolerance of DFG in 4H-SiC were calculated in the 2–15 THz range with different pumping wavelength. The output characteristics of THz generation were simulated in relation with the optical interaction length and the intensities of dual-wavelength pump beams via large-signal analysis among three coupled wave equations, which reveal that efficient and high energy THz generation based on 4H-SiC crystal could be achieved with appropriate crystal length and intensity ratio of dual-wavelength intense pumps, despite of a relatively low nonlinearity of the material.