Infrared-visible sum frequency generation (IR-Vis SFG) is a surface selective vibrational spectroscopy. As such, it is a powerful probe of the structure, interactions and chemistry of interface molecules between all phases. It can be usefully applied to a wide range of problems in fields such as catalysis, structural chemistry or photovoltaic device research.
IR-Vis SFG spectroscopy is under continuous development at the Ultra facility. We currently have a dedicated spectrometer, with built-in flexibility for different optical configurations, including normal reflection or ATR, and different sample-types. The spectrometer uses as standard broad bandwidth IR pulses (>400 cm-1, 50 fs) and etalon-narrowed time-asymmetric 1 to 2 ps, 800 nm pulses, giving non-resonant background suppression.
There are many interesting directions in which to develop the IR-Vis SFG technique: imaging, time resolved (ms-s and ultrafast) and two-dimensional infrared. The 20 W 10 kHz titanium-doped sapphire laser system driving the experiment allows multiple OPAs to be driven and an IR pulse shaper is available for spectral filtering and two-dimensional SFG spectroscopy.
