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.
Here are more examples of edge filters:
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