Covariance-based spectroscopy (IMAGE)
Caption
a, A schematic illustrating the paradigmatic difference between mean-value and covariance-based spectroscopy. The covariance-based approach extracts the information embedded in pulse-to-pulse fluctuations, which mean-value ignores. b, In a pump-probe experiment, the pump pulse drives a system out of equilibrium. The noisy probe pulse records the state of the system at a later time through correlations induced by a nonlinear interaction with the sample. c, A diagram of the experimental apparatus in which a pulse-shaper introduces fluctuations in the probe pulse, which then interacts with the sample before being recorded by a spectrometer. Comparison with the reference pulse reveals the correlations induced by the sample. d, The vibrational modes are revealed as signals that oscillate between positive (red, correlated) to negative (blue, anti-correlated) as a function of the time delay between pump and probe. e, Among other areas, this covariance-based approach promises to be useful in 2D-Raman spectroscopy, as demonstrated by this pseudo-2D Raman spectrum.
Credit
by Giorgia Sparapassi, Stefano M. Cavaletto, Jonathan Tollerud, Angela Montanaro, Filippo Glerean, Alexandre Marciniak, Fancesca Giusti, Shaul Mukamel and Daniele Fausti
Usage Restrictions
Credit must be given to the creator.
License
CC BY