OPTICAL BANDPASS FILTER, OPTICAL COMMUNICATION MODULE USING THE SAME, AND MANUFACTURING METHOD OF OPTICAL BANDPASS FILTER

摘要

PROBLEM TO BE SOLVED: To provide an optical bandpass filter reduced in insertion loss and excellent in optical characteristics, and to provide an optical communication module using the optical bandpass filter. SOLUTION: The optical bandpass filter is made by laminating a plurality of dielectric films 84 and 85 having different refractive indexes on an optical substrate 81 and the total film thickness of the films 84 and 85 is set equal to or greater than 50μm. Average surface roughness Ra of the surface of the substrate 81 side on which the dielectric films are provided is made equal to or less than 0.50 nm when the roughness is obtained by measuring a plurality of measurement points having measurement distances equal to or less than 100 nm. Note that the average surface roughness Ra is measured by scanning an area of 10μmx10μm employing an interatomic force microscope (an AFM). COPYRIGHT: (C)2005,JPO&NCIPI