PURPOSE: To realize an optical information processor which employs a semiconductor laser and is small in size, light in weight and low in cost.

CONSTITUTION: A semiconductor laser 21 and an LiTaO3 substrate 22 on which an optical waveguide 2 and a grating are formed are provided. A beam from the semiconductor laser 21 enters the optical waveguide and is partially fed back by the grating to generate an oscillation with a stable wavelength. The beam is converted into a parallel beam by a Fresnel lens 35 and condensed by a Fresnel lens 36 through a beam splitter 41. With this constitution, the wavelength of the semiconductor laser is not varied even if a current or an ambient temperature is varied and, in the condensation by the Fresnel lens, a stable operation can be performed without aberration and the reduction of size, weight and cost can be realized.