PURPOSE: To provide a light reflector used for a variable wavelength laser with the wavelength changed over a wide wavelength range so as to enable laser oscillation.

CONSTITUTION: A light reflector formed at an optical waveguide is of such structure that the equivalent refractive index changes in the macroscopically monotonous state with a fixed long cycle along the light propagated direction and that the equivalent refractive index repeats microscopic fluctuation along the macroscopically monotonous change inside the long cycle.