Mode-selective optical Kerr effect spectroscopy

We demonstrate that by using two pump pulses with independently controllable polarizations, intensity, and timing, different contributions to the optical Kerr effect (OKE) signal in liquids can be enhanced and suppressed. When both pump pulses have the same polarization, intramolecular vibrations can be enhanced or suppressed without affecting the reorientational diffusion contribution to the signal significantly. Similar control can be exerted over intramolecular vibrations when the pump pulses are perpendicularly polarized, and under these conditions it is also possible to suppress the reorientational diffusion component of the signal completely. When two intramolecular vibrational modes are present in the signal, it is possible to enhance one while completely suppressing the other if the pump polarizations and timing are chosen appropriately. This technique should be a useful means for enhancing contrast in OKE microscopy.