25 February 2004 Metal-dielectric coatings for variable transmission filters with wide rejection bands
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Metal-dielectric coatings are able to give high rejection in a wide wavelength range due to the reflection effect of metal layers. At the same time it is possible, according to the theory of induced transmission filters, to reach a quite high transmission peak at a single wavelength, starting from a metal layer and adding appropriate dielectric matching layers. Following this theoretical approach, narrow band-pass (10nm) filters having a peak transmission of 70% and a rejection out-band with extreme wavelengths in the ratio 2.5:1, are designed for the visible-near infrared spectrum. The low number of layers makes them interesting when a spatial variable filter has to be realized in a small dimension. Examples of their optical behavior at different wavelengths are reported.
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Angela M. Piegari, Vesna Janicki, "Metal-dielectric coatings for variable transmission filters with wide rejection bands", Proc. SPIE 5250, Advances in Optical Thin Films, (25 February 2004); doi: 10.1117/12.513402; https://doi.org/10.1117/12.513402

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