  We demonstrate an efficient procedure for terahertz-wave radiation generation
by applying a nonlinear wavelength conversion approach using a mid-infrared
pump source. We used a 3.3 {\mu}m dual-chirped optical parametric amplification
source and a 1.5 {\mu}m fiber laser for a comparison of energy conversion
efficiencies. Nonlinear inorganic and organic crystals were used, and for the
periodically-poled lithium niobate crystal, the efficiencies were 1.3*10^-4 and
5.6*10^-12 for the 3.3 {\mu}m source and the 1.5 {\mu}m source, respectively.
We confirmed that nonlinear crystals could be pumped with tera-watt / cm^2
class by using an mid-infrared source, which reduces several undesirable
nonlinear optical effects.
