There are provided: a core section provided so as to extend in a light-guiding direction in which incident light propagates; a photosensitive layer provided so as to extend in the light-guiding direction and peripherally enclose the core section, the photosensitive layer including a grating formed therein by irradiation of ultraviolet light having a predetermined wavelength; and a first cladding section provided between the core section and the photosensitive layer, the first cladding section having a lower refractive index than the core section and a lower photosensitivity than the photosensitive layer, the photosensitivity being a property in which a refractive index changes in response to irradiation with the ultraviolet light.