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This filter transmits a fairly narrow band of wavelengths centered at 870 nm.
This design is for normal incidence on a BK7 (ordinary) glass substrate.
Three materials are used: Au, SiO2, and TiO2. Starting with a thin, one-layer
design, TFCalc's needle/tunneling method produced a sequence of designs
of increasing complexity. The design (whose performance is shown above)
consists of 8 layers. Designs with as few as 4 layers are possible. However,
those designs have lower transmittance and a wider pass band.
Here is the design, with the first layer closest to the substrate and
thickness given in nm:
AU 23.33
SIO2 121.94
TIO2 94.24
SIO2 302.57
TIO2 94.24
SIO2 127.87
AU 24.97
TIO2 101.94
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