Two-dimensional Fourier-transform optical spectroscopy is demonstrated on GaAs quantum-wells. The signal is measured phase coherently with respect to the evolution time, enabling Fourier analysis. Coupling between heavy and light hole excitons yields cross-peaks.
We demonstrate three-dimensional (3D) electronic Fourier transform spectroscopy of GaAs quantum wells using four fully phase-coherent, noncollinear optical fields. Since the full complex signal field is measured as a function of all three time intervals, nearly every peak in the resulting 3D spectral solid arises from a distinguishable sequence of transitions represented by a single Feynman pathway. We use the 3D spectral peaks to separate two pathways involving weakly bound mixed biexcitons generated in different time orders. In the process, we reveal a peak that was previously obscured by a correlated but unbound exciton pair coherence. We also demonstrate a calibration procedure for the carrier frequency which yields biexciton binding energy values with high accuracy.
Multiple-quantum two-dimensional Fourier transform optical (2D FTOPT) spectroscopy was developed and conducted on GaAs quantum wells. Spatiotemporal femtosecond pulse shaping was used to control the optical phases and time delays of ultrashort pulses in multiple non-collinear beams so that fully coherent four-wave and higher-order mixing measurements could be conducted without delay stages, multiple interferometers, or any active phase control. Coherences of biexcitons, unbound but correlated exciton pairs, and excitons undergoing rephasing were observed directly.
Multiple-quantum two-dimensional Fourier transform optical (2D FTOPT) spectroscopy was developed and conducted on GaAs quantum wells. Spatiotemporal femtosecond pulse shaping was used to control the optical phases and time delays of ultrashort pulses in multiple non-collinear beams so that fully coherent four-wave and higher-order mixing measurements could be conducted without delay stages, multiple interferometers, or any active phase control. Coherences of biexcitons, unbound but correlated exciton pairs, and excitons undergoing rephasing were observed directly.
Electronic structure and dynamics are captured by optical 2D-Fourier-transform (2DFT) spectroscopy, which tracks the phase of the nonlinear signal during two time delays of a multi-pulse excitation sequence. These Fourier-transformed spectra separate and isolate overlapping and competing contributions to the coherent response. We have developed an ultra-stable platform consisting of nested interferometers with active phase control, allowing for exploration of single- and two-quantum coherences. Phase-resolved spectra are retrieved by all-optical determination of experimental phase ambiguities. GaAs quantum wells show suppression of many-body interactions in cross-linear polarized 2DFT spectra and many-body two-quantum coherences. Potassium vapor also shows unexpected two-quantum coherences.