| 摘要 |
There is provided a slant short-period grating which is obtainable by irradiating light onto an optical fiber whose core is formed from quartz glass to which has been doped a photosensitive dopant that changes a refractive index of the quartz glass by light irradiation, and whose clad has one or two or more layers with at least the layer that is adjacent to the core being a photosensitive layer formed from quartz glass to which has been doped a photosensitive dopant that changes a refractive index of the quartz glass by light irradiation. In this slant short-period grating a grating portion is formed by changing the refractive index of the photosensitive layer of the clad and the core at a predetermined grating period along a longitudinal direction of the optical fiber by a predetermined slant angle. The diameter of the core is set to 5 mum or more, and the relative photosensitivity ratio of the core relative to the photosensitive layer of the clad that is adjacent to the core is designed so as to satisfy a predetermined formula. As a result, in the wavelength spectrum of transmitted light, loss peaks are obtained in a narrow frequency band.
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