In-line reference measurement for surface second harmonic generation spectroscopy

Surface second harmonic generation (s-SHG) spectroscopy is a powerful tool to investigate layers or adsorbates on surfaces with high sensitivity. For this nonlinear technique, sophisticated reference methods are needed to properly treat the measured raw data. We present an easy-to-implement reference measurement method for s-SHG spectroscopy for surface layers or adsorbates. It directly allows for extracting reference-corrected s-SHG spectra from raw data. SHG from thin slabs of BK7 and MgO in the spectral range from 450 to 900 nm (fundamental beam) is used to obtain the reference spectrum. The method includes the experimental determination of the dispersive properties of the optical setup over the relevant spectral range. The accuracy of the presented procedure is demonstrated by applying the method to the study of a thin molecular filmof 1, 1'-Bi-2-naphthol (Binol) supported on a BK7 substrate.