Design and fabrication of mode size adapter in a photosensitive polymer waveguide

In this letter, we show the possibility to create by a photoinscription method a refractive index taper, in a photosensitive polymer waveguide, in order to reduce the coupling losses during connection to a single-mode optical fiber. The process uses the postirradiation of the guide by an ultraviolet source to gradually decrease the refractive index from the guide to the fiber. The losses decrease is controlled in situ in real time.