High performance narrow band-pass filter(NBF) designed for dual-band infrared(IR) detectors of near-infrared(NIR) and
mid-wavelength infrared(MWIR) application is presented. As the part of dual-color filters, the filter features a high
transmittance at the center wavelength of 1.55μm and a broadband rejection out of the pass band from 1 to 5μm. The
pass band need to be centered in 1.55±0.03μm, have a full width at half maximum of less than 0.055μm and maximum
transmittance higher than 75% when measured at normal incidence. Thin-film design for the filters is investigated in
detail and two kinds of multilayer schemes are obtained by computer optimization. Both consist of a fundamental
narrow-band filter of Fabry-Perot cavity with Si/SiO2 and Ti3O5/SiO2 as the material pair, respectively, and three edge
filters with the material pair of Si/SiO2 for wide band rejection. Moreover, the preparation of the filters have been given,
including the deposition parameters and especially, the optical thickness monitoring of the stack of Fabry-Perot cavity.
Finally, the filters meeting the requirements are accomplished and characterized, which have the peak transmittance of
about 82%, a full width at half maximum of 0.050μm and a broadband rejection with the average transmittance lower
than 1% from 1 to 5μm.