Two-dimensional circularly polarized pump-probe spectroscopy

A novel two-dimensional (2D) circularly polarized (CP) pump-probe (PP) spectroscopy is theoretically studied and proposed. Utilizing circularly polarized pump field, one can measure both the left- and right-CP PP spectra in the 2D frequency space spanned by the pump and probe field frequencies. Although the dominant contribution to the measured signal is all electricdipole-allowed four-wave-mixing term, it can be removed by taking the difference between the left- and right-CP PP signals. Taking the first-order terms with respect to either magnetic dipole- or quadrupole-pump field interaction, we find that two distinctively different contributions to the third-order CP-PP polarization are important. However, by controlling the crossing angle between the pump and probe field propagation directions to be the magic angle, theta=tan(-1)(1/root2), it is shown that the magnetic dipole-field interaction contribution to the third-order polarization can be selectively measured. It is observed that the relationship between the linear polarization PP and CP-PP is similar to that between the linear absorption and circular dichroism. Numerically calculated 2D CP-PP spectra for model systems are presented and compared with the absorption, circular dichroism, and linearly polarized PP spectra. (C) 2003 American Institute of Physics.