Sensitive absorption measurements in bulk material and coatings using a photothermal and a photoacoustic spectrometer

Bulk and surface absorption in lithium triborate (LBO) and lithium niobate (LiNbO3) are measured using two sensitive measurement techniques, a photoacoustic spectrometer (PAS) and a photothermal common-path interferometer (PCI). As pump light sources, optical parametric oscillators are employed, covering the wavelength ranges 212 − 2500 nm (PAS) and 1460 − 1900 nm and 2460 − 3900 nm (PCI). The spectrometers are used to measure absorption spectra of optical materials across this wide spectral range and to compare the methods in the shared wavelength regime.