A structure includes a combination of a stub fabricated on a polymer and a groove fabricated on a silicon (Si) chip, with which an adiabatic coupling can be realized by aligning a (single-mode) polymer waveguide (PWG) array fabricated on the polymer with a silicon waveguide (SiWG) array fabricated on the silicon chip. The stub fabricated on the polymer is patterned according to a nano-imprint process along with the PWG array in a direction in which the PWG array is fabricated. The groove fabricated on the silicon chip is fabricated along a direction in which the SiWG array is fabricated.