Method of forming refractive index distribution in light transmission path, and optical filter and method of using the same

摘要

A method of forming a refractive index distribution in a light transmission path is adapted to apply a photosensitive material layer (3) to the surface of a clad layer (2, 2a), form a mask pattern (3a) of the photosensitive material layer through photolithography, and irradiate a light transmission path (10, 10a) with an electromagnetic wave having a wavelength not exceeding that of visible light through the mask pattern (3a), thereby forming a refractive index fluctuation distribution corresponding to the mask pattern (3a) in a core (1).