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Keywords:

  • FTSI-CARS;
  • CARS microscopy;
  • sensitivity;
  • shot-noise-limit;
  • chemical imaging

Abstract

We report significant improvements in both signal sensitivity and imaging speed of Fourier transform spectral interferometry coherent anti-Stokes Raman scattering (FTSI-CARS) microscopy. With a help of an apodization function in the signal retrieval process, background due to the spectral change of nonresonant signals is eliminated. We experimentally verify that the sensitivity of the improved method is nearly shot-noise-limited. The current maximum detection sensitivity is ∼10 mM of aqueous sulfate ions, which correspond to ∼106 oscillators in the microscopy focal volume. Operating the charge-coupled device (CCD) in the crop mode increases the image acquisition speed by more than ten times. A vibrational hyperspectral image of a polymer sample with 100 × 100 pixel can be obtained within 3 s. With the improved sensitivity and speed, we also perform three-dimensional volume imaging. Superior chemical selectivity is demonstrated with a mixture of two different oil droplets, which have identical vibrational peak positions but different relative peak ratios. Copyright © 2010 John Wiley & Sons, Ltd.