WAVELENGTH FILTER, VARIABLE WAVELENGTH FILTER, AND OPTICAL ELEMENT

摘要

PROBLEM TO BE SOLVED: To provide a wavelength filter and its optical element which perform reflection in a sufficiently wide frequency band for communication, to provide a variable wavelength filter and its optical element which perform reflection in a sufficiently wide frequency band for communication and are variable in wavelength selectivity, and to provide an optical element which can sufficiently reduce a reflection factor not in a desired frequency band for communication. SOLUTION: The wavelength filter 1 has a plurality of grating filters 12 arranged at a given distance along the optical axis. The grating filter 12 is constituted by arraying substances differing in refractive index alternately (a high-refractive-index area 12a and a low-refractive index area 12b) at right angles to the optical axis 10. The refractive indexes of those substances 12a and 12b are both larger than that of an optical waveguide 14. The pitch of the array is an intervalΛshorter than a target wavelengthλ0. A plurality of wavelength filters 1 like this are constituted in a multiple stages. COPYRIGHT: (C)2004,JPO