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3D profiling of rough silicon carbide surfaces by coherence scanning interferometry using a femtosecond laser.

We test an erbium-doped fiber femtosecond laser for its potential as a light source for a coherence scanning interferometer for large field-of-view profiling of rough silicon carbide (SiC) surfaces. This infrared fiber pulse laser is able to provide a relatively long temporal coherence length of ∼30  μm to be appropriate for coherence scanning of rough surfaces. At the same time, it offers a high degree of spatial coherence comparable to that of a monochromatic continuous wave laser to achieve a large measurement field of view. In addition, the highly maintained linear polarization of the pulse laser source permits overcoming the low specular reflectance of rough SiC surfaces by polarization-based optical power splitting control between the reference and measurement arms.