METHOD FOR FORMING SPOT SIZE CONVERTING PORTION

摘要

PURPOSE:To enable local heating for forming a core enlarged portion by subjecting only that portion of the optical waveguide line at which its core is enlarged to laser beam machining. CONSTITUTION:The diameter of a core 9 positioned near the end portion of an optical waveguide line is made larger than the core diameter of the portion of the optical waveguide line positioned in other positions so as to form a core enlarged portion and also the core refractive index at the core enlarged portion is made lower than that at the portion of the optical waveguide line in other positions except those near the end portion and one part of the optical waveguide line is heated by laser 7 at the time of forming a spot size converting portion which enlarges spot size at the core enlarged portion. In this case, the higher the power with which CO2 laser 7 for example is applied, the larger the core diameter of the core enlarged portion is and the lower the refractive index of the core becomes. The spot size of waveguide light at the core enlarged portion is therefore enlarged by raising the power with which the CO2 laser 7 is applied.