Design and preparation of a 33-layer optical reflection filter of TiO2-SiO2 system

Multilayer optical reflection filters with several kinds of graded refracti ve index profiles were designed. The effects of the number of layers of mul tilayer films and grading functions of refractive index profiles on the opt ical filter characteristics were examined by using simulation. A 33-layer o ptical reflection filter with a linear refractive index profile was found t o be optimal in terms of both optical performance and manufacture. The desi gned 33-layer TiO2-SiO2 reflection filter was fabricated by helicon plasma sputtering. The optical performance of the prepared multilayer film agreed well with that of the designed filter. The measured transmittance spectrum exhibited a sharp cutoff stop band around a central wavelength of 1340 nm a nd a wide pass region with high transmittance of about 90%. The reflectance of the stop band was greater than 99.0% in the wavelength region from 1208 to 1518 nm. (C) 2000 American Vacuum Society. [S0734-2101(00)01403-2].