PROBLEM TO BE SOLVED: To obtain the optical device excellent in heat resistance and light transmittance in long wavelength by forming the core and/or clad of the array waveguide grating with the compd. contg. a fluorinated polyimide as the main component. ;SOLUTION: An input waveguide, a first slab waveguide, an array waveguide grating, a second slab waveguide and an output waveguide are optically connected in succession to obtain the optical device. The core and/or clad of the array waveguide grating is formed by the compd. contg. a fluorinated polyimide as the main component. The fluorinated polyimide is prepared by the reaction between a compd. expressed by formula I and a diamine shown by H2N-R-NH2, where R is a fluorinated or non-fluorinated bivalent org. group. The difference between the birefringence of the fluorinated polyimide constituting the core and that constituting the clad is controlled to ≤0.002.;COPYRIGHT: (C)1998,JPO
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