Pulse shaping based two-dimensional electronic spectroscopy in a background free geometry.

We demonstrate a "drop-in" modification of the pulse-shaped pump-probe geometry two-dimensional Fourier transform spectrometer that significantly improves its performance by making the measurement background-free. The modification uses a hybrid diffractive optic/pulse-shaping approach that combines the advantages of background-free detection with the precise timing and phase-cycling capabilities enabled by pulse-shaping. In addition, we present a simple new method for accurate phasing of optically heterodyned two-dimensional spectra. We demonstrate the high quality of data obtainable with this approach by reporting two-dimensional Fourier transform electronic spectra of chlorophyll a in glycerol/water at 77 K.