Abstract
We demonstrated a Cherenkov-type phase-matching method for monochromatic THz-wave generation using the difference frequency generation process with a lithium niobate crystal. In Cherenkov-type phase-matching process, when the bulk lithium niobate crystal is used, the beam diameter of pump waves causes the phase mismatching for generating THz-wave. We decreased the phase-mismatch by optimizing the pump beam shape with cylindrical lenses, and ensured high conversion efficiency especially in the high-frequency region. We successfully generated monochromatic THz waves across the 0.2- to 4.0-THz range with a simple configuration.