Verifying laser line rejection for Raman spectroscopy means proving three separate things, not one: the optical density at the laser wavelength under the angle and beam geometry the filter actually sees, the spectral distance between the laser line and the point where transmission recovers (expressed…
For a symmetric all-dielectric filter on a non-absorbing substrate, used near normal incidence at low optical power, flipping the part does not change the transmitted spectrum. Transmittance through a non-absorbing multilayer is the same in both propagation directions at the same angle of incidence. Optical…
A filter described as “850 nm,” “550 nm longpass,” or “10 nm bandpass” is not fully specified by those nominal numbers alone. Real optical filters are manufactured and measured against an allowable range. A nominal 850 nm bandpass filter, for example, may require its actual…
