Nonresonant background suppression in broadband vibrational sum-frequency generation spectroscopy

Suppression of the nonresonant background in vibrational sum-frequency generation (SFG) in the broadband multiplex configuration is achieved using a time-asymmetric pulse, created by passing a femtosecond pulse through a Fabry-Perot etalon, to temporally discriminate between the faster nonresonant and slower resonant contributions. A mixed time and frequency domain explanation of the SFG process is presented, and spectra with high time resolutions and high degrees of nonresonant background suppression are obtained using self-assembled alkanethiolate monolayers on Au.