Edge Filters

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There are two types of edge filters: Long Wave Pass and Short Wave Pass. In the long wave pass filter, the goal is to minimize transmission below a given wavelength and maximize transmission above it. These designs are usually based on a quarter-wave stack (HL)^p, which has a well-defined transition from reflecting to transmitting. Sometimes absorbing materials are used to increase the optical density of the non-reflecting (rejection) band of the filter. In the short wave pass filter, the goal is to minimize transmission above a given wavelength and maximize transmission below it.

The graphic below shows the performance of a 37-layer short wave pass filter.

Plot of edge-filter performance

Here are more examples of edge filters:
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