Edge filters are required when defined portions of the light spectrum are to be suppressed or two spectral ranges are to be separated from each other. The steep transitions from pass to cutoff range are characteristic here. Edge filters are long-pass filters or short-pass filters (allow longer or shorter wavelengths than the cut-off wavelength to pass).
LAYERTEC manufactures edge filters for laser applications using sputtering technologies. Here, the lowest optical losses, a maximum damage threshold and the targeted compliance with beam properties are important product criteria.
For price-sensitive components, the minimum spectral separation between the maximum and minimum transmission should not fall below 4 percent of the cut-off wavelength at R = T = 50 %. For example, a short-pass filter for the pump optics of a ps laser with R(0°,960 - 990 nm) < 2 % + R(0°,1030 - 1055 nm) > 99.9 % meets this requirement.
Fast and cost-effective fabrication of extremely steep edge filters, e.g. for university experiments, is achieved if the spectral position of the filter can be adjusted in the experiment by fine angle adjustment, e.g. in the range ±4° for a nominal incidence angle of 12°.