It is an object of the present invention to provide a short-wavelength
coherent light source that includes a semiconductor laser and a wavelength
converting device and is controlled to have a desired wavelength. The
coherent light source includes the following: a semiconductor laser having
a first wavelength; an optical waveguide-type QPM-SHG device used as a
wavelength converting device for converting the wavelength of the
semiconductor laser by half; a wavelength separating function; a
diffraction grating; and a photo-detector. The semiconductor laser beam
acting as fundamental light is separated with the wavelength separating
function, and the wavelength is controlled with the diffraction grating.
Thus, the wavelength of harmonic light generated by wavelength conversion
is controlled to a desired wavelength.
