Novel OPCPA based source for broadband high resolution sum frequency generation spectroscopy

Summary form only given. Sum frequency generation (SFG) spectroscopy is a powerful technique for characterization of vibrational bonds of molecules at surfaces and interfaces [1]. The principle of SFG is based on resonant nonlinear mixing of two optical pulses - typically one in MIR range and another visible (VIS). There are two main SFG spectroscopy techniques. Narrowband SFG (NB-SFG) is based on picosecond MIR and picosecond VIS source. Full spectral information is obtained by tuning MIR pulses through vibrational lines of the molecules. The typical resolution in NB-SFG is a few cm<;sup>-1<;/sup> [2]. In broadband SFG (BB-SFG) femtosecond MIR pulses with spectrum spanning a few hundred cm<;sup>-1<;/sup> are used. This allows for simultaneous recording of complete SFG spectra and reduces systematic errors due to sample degradation during the measurement. However in most experimental BB-SFG setups the same femtosecond laser source is used to produce narrowband VIS pulses. Therefore typical resolution obtained with BB-SFG is ~10-20 cm<;sup>-1<;/sup> which limits ability to analyze vibrational line-shapes [2]. Finally a hybrid system was demonstrated where two separate laser sources - femtosecond and picosecond - were synchronized to achieve both very high spectral resolution (<;1cm<;sup>-1<;/sup>) and simultaneous spectral recording [3]. However the system required two complex independent synchronized laser systems which would be difficult to implement in most laboratories.In this work we developed novel OPCPA based laser source which provided both narrowband ~10 ps duration VIS channel (532 nm) and broadband (>700cm-1) femtosecond MIR channel. The OPCPA system was described recently [4]. The block diagram of the experimental system is presented in Fig. 1(a). Recorded SFG spectrum of glucose using the described system as well as classical NB-SFG system is presented Fig. 1(b). The obtained resolution in both cases was ~6 cm-1.This demonstrates the usability of the OPCPA based source to perform BB-SFG with high resolution. Much more details on the laser system and SFG spectrometer will be provided at the conference.