LIGHT GUIDE DEVICE

PURPOSE:To obtain a light guide device which has high waveguide efficiency and small loss of coupling with a large-diameter optical fiber by joining plural light guide substrates which differ in waveguide width stepwise and thus forming a waveguide whose section is nearly circular. CONSTITUTION:High polymer waveguide films 12-21 each have a light guide part 24 of waveguide width W composed of a photopolymerizing part 22 which forms a clad and a nonphotopolymerizing part 23 which forms a core. The width W is made different stepwise successively, and the films are laminated and joined by adhesive layers 25 so that the section of the whole waveguide is nearly circular. Coat layers 26 and 27 are provided on the top and reverse surfaces of the jointed body. Consequently, the light guide device 29 which has the large- diameter light guide part 28, high waveguide efficiency, and small loss of coupling with the large-diameter optical fiber is obtained.