Cavity-like filters with absorbing layers.

Two narrowband filter types are presented: narrowband reflector and narrowband absorber. Both are related to the familiar narrowband pass cavity filter, but include a thin absorbing layer.

Narrowband angle filter.

Narrowband pass filters are generally poor as narrowband angle filters. A tilted narrowband pass filter, however, is an improved narrowband angle filter, but only for rays in one plane of incidence. It is shown that a combination of two tilted narrowband pass filters will select light from all narrow angle patches in an incident cone.

Flip-flop coating synthesis revisited.

The flip-flop synthesis method is robust with rapid convergence, but the solutions are often not the best. Modifications to the flip-flop algorithm have been developed, one of which puts it on par with needle synthesis.