An optical assembly for use in coherent two- or more-dimensional optical spectroscopy includes a beam splitter that splits a base light pulse into first, second, third and fourth light pulse and a delay element that varies the arrival times of the first to fourth light pulses at a sample location with respect to each other. The beam splitter includes a cross-grating a first reflector arranged to receive the first to fourth light pulses emerging from the cross-grating and to reflect the same in parallel to each other, a second reflector arranged to receive the first to fourth light pulses from the delay element and to focus the same at the sample location, wherein the delay element is arranged between first and second reflectors. Also shown is an apparatus including such optical assembly and a method for carrying out two- or more-dimensional optical spectroscopy using the assembly.