A fast-scanning Fourier transform 2D IR interferometer

Ultrafast two-dimensional infrared spectroscopy (2D IR) allows for the characterization of vibrational couplings and chemical dynamics. The fastest method of acquiring a Fourier transform 2D IR data set involves spectrally dispersing the signal field onto an infrared array detector. However, use of this method carries disadvantages, including the high cost of IR arrays and the decrease of signal intensity due to dispersion. As an alternative, we demonstrate a readily implemented full time-domain 2D IR detection method in which data from a pulsed laser source is rapidly acquired by scanning an interferometer delay at constant velocity. The stage's position is determined with high accuracy on a shot-to-shot basis by quadrature detection of HeNe tracer interference fringes.

Research Highlights
► A new methodology for the acquisition of time domain 2D IR spectra is detailed.
► Constant velocity scanning is used to rapidly sweep time delays.
► Stage positioning is tracked on a shot-to-shot basis with a HeNe alignment beam.
► A comparison between time domain and mixed time–frequency acquisition is given.
► For weak signals, time domain acquisition shows high signal-to-noise.