Enhanced-Resolution Single-Shot 2DFT Spectroscopy by Spatial Spectral Interferometry

Abstract

We demonstrate use of spatial interference for the complete electric field reconstruction of two-dimensional (2D) coherent spectroscopic signals generated through four-wave mixing (4WM) in a single laser shot. Until now, the amplitude and phase characterization of 4WM signals has relied primarily on Fourier transform spectral interferometry (FTSI), which limits the measurement's sensitivity and resolution. We show that spatial spectral interferometry (SSI) is a generalized approach to 4WM signal detection that eliminates these inherent limitations of FTSI without introducing additional experimental complexity. SSI is used to measure the 2D photon echo spectra of two systems with dramatically different line widths, the coupled D line transitions in rubidium vapor and the energy-transfer dynamics in the light-harvesting protein LH2.

Quantum coherence selective 2D Raman–2D electronic spectroscopy

“…The spatial-interferometry pulse tilt correction41 is applied to the images to remove the phase introduced by the wavefront tilt between pulse 3 and the local oscillator (pulse 4), and the images are interpolated along the detection axis onto a grid of equally spaced frequency points. At this point, 6WM 2DFT electronic slice spectra can be generated.…”

Mapping multidimensional electronic structure and ultrafast dynamics with single-element detection and compressive sensing

“…1 of ref. 14 for details on the beam geometry). The laser centre wavelength was tuned to 775 and 825 nm for measurements on IR-144 and LH2, respectively.…”

“…Transformed interferograms are subsequently cropped to the extent of the active area of the DMD spatial mask. The τ axis is calibrated by measuring the spatial spectral interference between beams 1 and 2 using the spectrograph camera, as previously described 14 . The signal-beam 4 interferograms are (piecewise cubic) interpolated from a grid of equidistant wavelengths to a grid of equidistant frequencies.…”

“…To make this connection, we begin by noting that the signal measured in 2D PES is typically sparse (that is, compressible). In most cases, the phase of the nonlinear signal, which is needed to extract the oscillation frequencies of the system, is measured by spectral interferometry in which an external reference field is coherently mixed with the signal and spectrally dispersed onto a detector 11 12 13 14 . Heterodyne detection yields an interferogram that is sparse in one or more Fourier domains, and it is this sparsity that we exploit using compressive sensing (CS) methods.…”

“…Recently, some of the authors introduced a significantly higher-throughput sampling scheme called GRAPES 14 26 27 (GRadient Assisted Photon Echo Spectroscopy) that breaks with the traditional τ -scan approach. By incorporating a 2D array detector and a spatiotemporal gradient, all the τ delays may be sampled in parallel.…”