A device used to reject certain frequencies of light.
This refers to the filter transmittance outside the bandpass region, the degree to which undesired wavelengths are prevented from being transmitted. Filters with deep out-of-band blocking significantly enhance the signal-to-noise ratio of the system.
A multi-layer antireflection coating with reduced reflection over a broad spectral band.
For filters and coatings, the average of the wavelength values at the half-power points of the transmission band.