Terahertz wave source via difference-frequency mixing using cross-Reststrahlen band dispersion compensation phase matching: A material study

A novel phase-matching technique for coherent THz-wave generation was proposed. This approach uses cross- Reststrahlen band dispersion compensation phase-matching in a collinear optical mixing technique using isotropic, semiconductor nonlinear crystals. The pump and signal sources are in the near-IR transmission window of the nonlinear crystal and the generated idler wave is in the far-IR transmission window, on the other side of the crystal's Reststrahlen band. The choice of the nonlinear crystal for frequency conversion from the near-IR to the far-IR is highly dependent on the optical properties of the nonlinear crystal being used as the frequency converter element. We evaluate the use of the proposed phase-matching technique with a variety of III-V and II-VI compounds taking into account their optical dispersion and their phase- matching properties. Theoretical projections of the device performance such as perfect phase-matching conditions, coherence length and wavelength tuning range for different nonlinear crystals are compared.