The application discloses a method for realizing optical wave and terahertz near-zero
refractive index based on a nonlinear mixed
waveguide, and steps are as follows: thin film
lithium niobate is selected as a nonlinear material to process a mixed
waveguide; a one-dimensional corrugated
waveguide is used on the mixed waveguide to show a
Dirac point-like dispersion characteristic at a Gamma point; an average
nonlinear coupling coefficient of the mixed waveguide is calculated, and the quality factor of the zero-refractive-index waveguide is optimized by adjusting the thickness and period of the thin film
lithium niobate; hollow rectangular
metal waveguides are arranged around the thin film
lithium niobate waveguide, and are used for guiding the propagation of terahertz
waves and enhancing the nonlinear interaction in the difference frequency process; and the near-zero
refractive index of various terahertz frequencies is realized by changing the width of the hollow rectangular
metal waveguide. By jointly designing the nonlinear mixed waveguide of the terahertz and optical wave near-zero
refractive index, the problems of phase mismatch and weak nonlinear interaction of the conversion of the optical wave to the terahertz wave are solved, so that the efficient conversion of the optical wave to the terahertz wave across the
wave band is realized through on-
chip optical difference frequency.