Reliable substrate characterization in the broadband range of 220-1700 nm based on spectral photometric data

Accurate knowledge of the substrate optical properties is crucial for the theoretical designing and monitoring of optical coatings and characterization of produced optical coatings. Typically, substrate characterization is performed based on reflectance and transmittance data in the relevant spectral range. Measurement errors (offsets of spectral characteristics and noise) are inevitable. Neglecting scattering and assuming transparent spectral ranges, offset values of experimental data can be estimated as a difference between 100% and the sum of the measured transmittance and reflectance. It doesn't provide insights into which spectral characteristic(s), reflectance, transmittance, or both, contribute to the offset or to what extent. We suggest an approach that allows one to estimate the offset values in reflectance and transmittance separately, estimate the effect of these offsets on the determination of substrate optical constants and characterize the substrates reliably. We demonstrate the approach characterizing various substrates in the range 220-1700 nm based on PHOTON RT measurements (EssentOptics).