APPARATUS AND METHOD FOR COHERENT MULTI-DIMENSIONAL OPTICAL SPECTROSCOPY

An apparatus and a method for coherent multi-dimensional optical spectroscopy employs a beam splitter for splitting a base light pulse into at least first to fourth light pulses, three of which are suitable for interaction with a sample, lens system focuses the first to fourth light pulses at a sample site, and an optical delay varies the arrival times of the first to fourth light pulses at the sample. A detector detects an interference signal. The beam splitter is a non-diffractive optical element. The light pulses, at least along part of their light paths, are guided pairwisely such that changes in the optical path length due to vibration of the beam splitter or due to the delay element are identical for each pair of pulses, where the pulse pairs compensate for any change in the interference signal due to a change of the arrival times of the pair of pulses.