Compact optical setup for forward-box degenerate four-wave mixing measurement

We have devised compact optics for the forward-box configuration in degenerate four-wave mixing spectroscopy. The core of the optical setup is the successive use of a pair of polarization-based beam splitters that divide the laser beam into four parallel beams. This setup is compact, easy to assemble, and adaptable for laser light over a wide spectral range. Selection of the combination of beam polarization produces two types of transient grating: either a polarization grating or an intensity grating. (C) 1999 American Institute of Physics. [S0034-6748(99)02711-2].