| CPC G02B 5/208 (2013.01) [C23C 14/0694 (2013.01); C23C 14/081 (2013.01); C23C 14/083 (2013.01); C23C 14/10 (2013.01); C23C 14/34 (2013.01); C23C 28/345 (2013.01); G02B 1/007 (2013.01); G02B 1/115 (2013.01); G02B 5/20 (2013.01)] | 20 Claims |

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1. An optical filter, comprising:
a first layer including a first material,
the first material including at least silicon and hydrogen;
a second layer including a second material that is different from the first material,
the second material including an oxide, and
the second layer being adjacent to the first layer;
a third layer including a third material that is different from the first material and the second material,
the third material including at least tantalum, and
the third layer being adjacent to the second layer; and
a fourth layer including the second material,
the second material in the fourth layer being adjacent to the third layer.
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