Spectrally resolved temporal coherence of spectrally narrowband filtered high-power supercontinuum light source versus an appropriately treated laser-driven plasma light source

For interferometric measurement methods such as optical white light interferometry, the coherence length of the implemented broadband light source is of central importance in order to realize a high axial resolution as well as a large dynamic range of the measurement system. In the case the broadband light sources are spectrally resolved by a spectral dispersive element, the spatial coherence and emission duration define primarily the coherence of the light source when no stimulated emission occurs. Broadband light sources with a high brilliance, such as supercontinuum and laser-driven plasma light sources, are particularly interesting for interferometric measurement methods because of their high spectral width and beam quality with enormous spectral power density. Especially for interferometric measurements, the coherence of the light source is essential. In the scope of the investigations, the coherence length and spectral power density of high-power supercontinuum light source based on a Yb-doped photonic crystal fiber in a nonlinear fiber amplifier setup and a commercially available laser-driven plasma light source were comparatively investigated with conventional white light sources. It was shown that the investigated high-power supercontinuum light source can be used very well for interferometric investigations. Furthermore, the achieved spectral pulse peak power densities exceed the laser-driven plasma light sources by a factor of one million.