AR-hard designs can be understood as step-down designs composed of layer stacks with low equivalent index. The AR bandwidth can be adjusted in accordance with the optical thickness used for each step.
© 2004 Optical Society of America
U. Schulz, N. Kaiser, and U. B. Schallenberg, " AR-hard broadband antireflective coatings generated by a controlled needle-optimization technique," in Optical Interference Coatings, OSA Technical Digest Series (Optical Society of America, 2004), paper TuB2.
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