Abstract: Recently picosecond vibrationally resonant sum frequency generation (VRSFG) process has been adopted as a surface sensitive, chemically specific nonlinear imaging modality. In this talk, we will discuss our recent efforts to extend this technique to femtosecond regime. To this end, we have built a high powered mid infrared femtosecond optical parametric oscillator (OPO) tunable from 3-5 micron range. Use of femtosecond laser pulses exploits the broad bandwidth of mid infrared pulses to multiplex spectrum measurement and time resolve vibrational free induction decay to study dynamics. Experimental results of time resolved free induction decay, spectra and images of collagen-I will be presented.