We propose, for the first time to our knowledge, a new feedback fabrication technique for rugate filters with sinusoidal refractive index distribution. The technique uses an in situ optical monitoring system, in contrast to conventional techniques for rugate filters that are based on time control, which is generally unsuitable for accurate fabrication of a continuous index distribution. We employed a-SiOx:H thin film as the material for the rugate filters because its refractive index can be successively controlled. Using the proposed technique and material, we fabricated near-infrared rugate minus filters having multiple and continuous refractive index distributions. The experimental and calculated spectra were well correlated as a result of applying the proposed feedback fabrication technique.
© 2005 Optical Society of America
(060.4510) Fiber optics and optical communications : Optical communications
(230.4170) Optical devices : Multilayers
(310.1860) Thin films : Deposition and fabrication
(310.3840) Thin films : Materials and process characterization
(310.6860) Thin films : Thin films, optical properties
Hidehiko Yoda, Daisaku Tanaka, Osamu Hanaizumi, Yoshinori Kogami, and Kazuo Shiraishi, "Rugate filters fabricated by a radio frequency magnetron sputtering system by use of an optical in situ monitoring technique," Appl. Opt. 45, 184-190 (2006)