JPS55110205A - Optical filter - Google Patents

Abstract

PURPOSE:To obtain the simple and highly reliable optical filter by forming the optical filter into the same shape as that of an optical fiber and so constituting the same that the matching of the coupling part of both may be taken. CONSTITUTION:Transparent dielectric 6 having a refractive index slightly higher than that of bar-form photosensitive material 5 such as photo polymer or amorphous semiconductor of the same core dimater and same diameter as an optical fiber is coated on the outside circumference of said photosensitive material 5. Next, when two broad beams B1, B2 which show sensitivity to the photosensitive material 5 are simultaneously radiated with an angle 2theta0 with each other through the transparent dielectric 6, the interference fringes of period LAMBDA shown in formula 1 i.e., grating images 7 are continuously exposed in the axial direction to the photosensitive material 5 through interference of the beams B1, B2. When the optical fibers 9, 10 of the same diameter as that of the photosensitive material 5 are directly bonded to the both ends of this optical fiber 8, only the light waves of the wavelength lambda shown in formula 2 are selectively reflected from the incident side. In this way, the simple and highly reliable optical filter is obtained.