Two Ramp Filters
As an interesting design exercise, we decided to create two ramp filters. The goal is to
create filters in which the transmittance increases (or decreases) linearly over some
wavelength range. Too make it slightly more difficult, we also require the transmittance
to be 0% and 100% on either side of the ramp.
Here are the specific requirements for the normal-incidence increasing-transmittance ramp filter:
We use the three continuous optimization targets. To find the thinnest possible design, we start with a single thin layer of TIO2 and use TFCalc's needle/tunneling optimization to design the filter from "scratch". Optimizing this design takes only a minute or two on a 2.8 GHz Pentium computer. The performance of the 23-layer design is shown here.
For the second design, we just replace transmittance by reflectance in the requirements. The performance of the filter, which also has 23 layers, is shown here.
If you want a copy of the design files, which will work in the demo version of TFCalc, please send e-mail to firstname.lastname@example.org.
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