Multi-branch 1-µm pumped mid-IR OPA for interface-specific nonlinear vibrational spectroscopy

Many important processes in chemistry and biology occur at interfaces. A powerful noninvasive, optical, surface analytical tool is vibrational sum frequency generation (VSFG) spectroscopy, which often enables the direct observation of the structural and dynamical properties of interfacial molecules. Nevertheless, the acquisition times and spectral resolution of traditional broadband VSFG spectrometers are far from ideal to follow the interaction of macromolecules at bio-interfaces in real time and in situ.
In the seminar, I will provide an overview of our mid-IR light sources integrated in our unique high-resolution 100-kHz VSFG spectrometer. By employing, for the first time, a high-repetition-rate diode-pumped Yb-laser/amplifier to drive such a spectrometer, the collection of vibrational spectra of biologically relevant monolayers and bilayers at air-solid and air-liquid interfaces has become possible at an unprecedented combination of signal-to-noise ratios and acquisition times at wavelengths up to 13.5 µm. The spectrometer also features a narrowband VIS beam line based on high-efficiency chirped sum-frequency mixing making it possible to disentangle previously unresolved vibrational bands. Our recent results and the unique parameters of our spectrometer offer great potential for chemical and structural analysis of novel 2D materials and complex biological samples with sub-monolayer sensitivity in the spectral range of 770-3800 cm-1.