Difference-frequency generation of THz radiation via parametric three-wave interaction in CdTe and ZnTe crystals

Difference-frequency generation of terahertz (THz) radiation in a collinear single-crystal scheme with distributed feedback implemented by means of parametric interaction of counterpropagating optical waves in a periodically inhomogeneous medium exhibiting quadratic nonlinearity is investigated. Using ZnTe and CdTe crystals optically pumped at $\lambda$ = 0.77 and 1.06 $\mu$m, respectively, as an example, the possibility of obtaining parametric generation of THz radiation with an optical-to-THz conversion efficiency exceeding 10$^{-3}$ (with an extremely narrow line of oscillation of less than 4 GHz for ZnTe and less than 9 GHz for CdTe at 1 THz) is demonstrated in the undepleted-pump-intensity approximation. The obtained results can be used for construction of narrow-band lasers in the THz frequency range with an output power (in the quasicw regime of oscillation) of about 10$^{5}$ W/cm$^{2}$.