Lower-Upper Polariton Interactions Proved with Two-Dimensional Fourier Transform (2DFT) Spectroscopy in Semiconductor Microcavity

Two-dimensional Fourier transform (2DFT) spectroscopy is a powerful tool commonly used for investigating anharmonic coupling between different molecular vibrational states [1]. We applied this technique to a GaAs based semiconductor microcavity for investigating interactions among lower (LP) and upper (UP) polaritons. The observed 1-quantum and 2-quatum 2DFT experimental spectra are presented in Fig. 1 (a, c). Both spectra show four peak groups that correspond to LP-LP and UP-UP (diagonal peaks) and LP-UP and UP-LP interactions (off-diagonal peaks). Inside each peak, a complex structure can be found.