CURVED OPTICAL WAVEGUIDE AND ITS PRODUCTION

摘要

PURPOSE:To suppress the propagation loss of a guided wave due to unevenness of an etching surface and the radiation loss due to the curvature by decreasing the thickness-directional equivalent refractive index of at least an outside clad nearby the curved part of a core with the increase of distance from the core. CONSTITUTION:The outside clad 5 is gradually reduced in thickness and an inside clad 6 is gradually increased in thickness so as to correct the refractive index distribution. Therefore, when this curved optical waveguide is mapped on a straight optical waveguide at an equal angle, the outside and inside refractive index distributions of the curved part in the section become constant. Further, the inclinations of the thicknesses of the clads 5 and 6 are so determined that the refractive index distribution becomes flat at the time of conversion into the straight optical waveguide by the equalangle mapping. In this case, the outside nearby part of the curved part is etched a little deeper than the inside nearby part so as to equivalently correct the inclination of the refractive index distribution generated at the mesa part of the curved part.