Laser-based assessment of optical interference filters with sharp spectral edges and high optical density

Interference filters have improved over the years. Sharp spectral edges (> 1 db/nm) reach high optical density (OD > 8) in a few nm. In-situ optical monitoring to within 0.1% error enables these levels of performance. Due to limitations related to f-number and resolution bandwidth, post-deposition testing in typical spectrophotometers cannot reveal the quality of today's filters. Laser based measurements at selected wavelengths prove that blocking above OD8 to OD9 is manufacturable with high yield. This paper compares modeled spectra and laser based measurements.