BEAM SHAPING OPTICAL SYSTEM

PURPOSE:To easily adjust this optical system by making incident light reflect on the surface of an optical prism where a gap layer which has a lower refractive index than the optical prism and a waveguide layer which has a higher refracting index than this layer are laminated. CONSTITUTION:A part of light reaching the interface between the prism 3 and gap layer becomes an evanescent wave, which is propagated in the waveguide layer 5 and light which does not become the waveguide light is reflected and emitted from the prism 3. The light which becomes the waveguide light while propagating in the waveguide layer 5 is reradiated partially to the prism 3 through the gap layer 4 and radiated from the prism 3. Thus the waveguide light has a beam diameter l0 rather than an incident beam diameter l1 and is nearly radiated and emitted from the prism 3. Namely, the beam with the width l1 which is made incident on a prism coupler 6 is emitted from the prism 3 to the waveguide layer 5 as a beam with the width l0. Consequently, the parallel light emitted from the prism 3 is converged by a condenser lens 7 as a beam almost in an isotropic shape to form a spot on an optical disk 8, so that the beam can easily be shaped.