Interferences Band Pass Filters (F)

• Precise control of bandpass
• Good out of band blocking
• Tunable by tilting

These interference filters are based on the Fabry-Perot effect. Stacks of highly reflective films provide selective interference to reinforce the transmittance at the wavelength of interest and to cancel at other wavelengths. The typical structure of these filters is two stacks of highly reflective layers, which are separated by a multiple half wave thick spacer. This pattern forms a cavity and typically two or three cavities are superimposed to reduce the half width of the transmission spectrum. Out of band wavelengths are blocked with a colored glass layer.