The properties of wavelength-division multiplexed (WDM) narrowband filters used in tilted collimated light are described. The wavelength shift for <i>s</i> polarization in a low-index-spacer filter is larger than that for <i>p</i> polarization when the filter is tilted, but it is smaller in a high-index-spacer filter. Therefore the passbands of the tilted filter can be centered at the same wavelength for two polarization modes by use of high- and low-index materials, as appropriate, as spacers or by selection of a moderate-index material instead of a spacer. With such spacers, WDM filters used for incident angles of 20° or even greater are constructed. Experimental results agree with the computed ones.
© 2004 Optical Society of America
(060.4510) Fiber optics and optical communications : Optical communications
(120.2440) Instrumentation, measurement, and metrology : Filters
(310.0310) Thin films : Thin films
(310.6860) Thin films : Thin films, optical properties
(350.2460) Other areas of optics : Filters, interference
Peifu Gu, Haixing Chen, Yueguang Zhang, Haifeng Li, and Xu Liu, "Wavelength-Division Multiplexed Thin-Film Filters Used in Tilted Incident Angles of Light," Appl. Opt. 43, 2066-2070 (2004)