Apparatus for generating tera-herz wave and tuning method

A tuning method of a THz-wave generation apparatus for allowing a pump light (2) to be incident upon a nonlinear optical crystal (1) which can generate a THz wave by a parametric effect and for generating an idler light (3) and THz wave (4) in a direction in which a non-collinear phase matching condition is satisfied, the method comprising the steps of:

• injecting the seed light (5) having a variable frequency in a generation direction of the idler light;
• and
• combining a wavelength dispersion element (17) for dispersing an optical path of the seed light because of a difference of a wavelength of the seed light with a dispersion enlargement/reduction element (18) for enlarging or reducing the dispersed optical path to constitute angle dispersion compensation means (16) so that an incidence angle θIN of the seed light upon the nonlinear optical crystal (1) substantially equals to a desired phase matching condition regardless of the wavelength.