Narrowband Filters

Classic line filters or narrowband filters are also called Fabry-Perot filters. They filter out a narrowband region from a broadband light spectrum. The first surface of a substrate is provided with a layer stack consisting of two highly reflective and one low-reflective layer. These form an optical resonator. An incoming laser beam is only transmitted if it satisfies the corresponding resonance condition.

By adjusting spacer thickness and number of reflection enhancing layers, we can target blocking and linewidth. We can supply filters with half-widths down to the picometer range.

Such single piece or small series filters can be manufactured at low cost, if the manufacturing tolerances are corrected during installation by means of angular adjustment. Otherwise, we recommend a filter set with spectrally slightly staggered transmission maxima. This minimizes the necessary angular adjustment for at least one filter in the set.