Fabrication of a 33-layer optical reflection filter with stepwise graded refractive index profiles
- PDF / 122,299 Bytes
- 4 Pages / 612 x 792 pts (letter) Page_size
- 25 Downloads / 182 Views
MATERIALS RESEARCH
Welcome
Comments
Help
Fabrication of a 33-layer optical reflection filter with stepwise graded refractive index profiles Xinrong Wang and Hiroshi Masumoto Institute for Materials Research, Tohoku University, 2-1-1 Katahira, Aoba-Ku, Sendai 980-8577, Japan
Yoshihiro Someno Mechatronic Devices Division 1, ALPS Electric Co. Ltd., 6-1 Aza, Nishida Kakuda, Kakuda, Miyagi Prefecture, 981-1505, Japan
Lidong Chen and Toshio Hirai Institute for Materials Research, Tohoku University, 2-1-1 Katahira, Aoba-Ku, Sendai 980-8577, Japan (Received 3 May 1999; accepted 10 November 1999)
A novel optical multilayer filter characterized by symmetrically stepwise graded refractive index profiles and high optical performance was designed. This 33-layer TiO2–SiO2 filter was fabricated by helicon plasma sputtering. The prepared filter exhibited a sharp cutoff reflection band around the central wavelength of 1340 nm and wide pass regions with high transmittance. These results correspond well with calculated estimations. Symmetrically stepwise graded refractive index profiles were demonstrated to effectively contribute to suppression of the sidelobes and to be potentially applicable in the design of other filters.
Dense wavelength division multiplexing (DWDM) technology is essential in high-speed and large-capacity optical fiber communication. Communication capability can be enhanced by development of the DWDM system in which many channels of different wavelengths of light are combined in a single fiber. In general, the different wavelengths of light in the regions around 800, 1300, and 1500 nm are used for propagation of optical signals in the short-, medium-, and long-distance areas, respectively, because of the low loss in the windows of glass located in these near-infrared regions.1 Therefore, development of optical devices used in the above wavelength regions has attracted considerable interest. An optical filter is an essential component of the DWDM system. To effectively separate channel waves, it is necessary to develop filters that exhibit high selectivity in the bandwidths in a certain wavelength area. To date, there have been many reports on theoretical analysis and experimental fabrication of optical filters.2–6 For the reflection filter, quarterwave stacks with alternating highand low-refractive index films are used as a filter with a reflection band in specific wavelengths; an advantage of such multilayer films is their ease of manufacture.7–9 However, the sidelobes attached to the simple quarterwave stacks detract from the transmission in the pass regions. To solve this problem, an effective theoretical design termed “rugate filter” has been developed in the 274
http://journals.cambridge.org
J. Mater. Res., Vol. 15, No. 2, Feb 2000 Downloaded: 14 Aug 2015
past decade. According to theoretical calculations, complex rugate filters can achieve excellent performance in reflection filters.10–12 Consequently, some experimental approaches to fabrication of rugate filters have been carried out by various
Data Loading...
