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Microscopy with undetected photons in the mid-infrared

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Science Advances  14 Oct 2020:
Vol. 6, no. 42, eabd0264
DOI: 10.1126/sciadv.abd0264
  • Fig. 1 Experimental setup and interference images.

    (A) A 660-nm continuous-wave laser pumps a highly nondegenerate SPDC process. The signal and idler fields generated on the first pass of the 2-mm ppKTP crystal are split via a dichroic mirror (DM). The sample to be imaged is placed in the Fourier plane of the idler, which coincides with its end mirror. Both the idler and signal fields are reflected back, recombined, and back-propagated into the nonlinear crystal with the coherent pump field. The resulting signal field is imaged on a CMOS camera. (B) Constructive, destructive, and difference interference images of the signal for a cardboard cutout probed by the mid-IR idler. Scale bar, 2 mm.

  • Fig. 2 Characterization of the imaging arrangements.

    The images and data of the unmagnified and magnified setups are presented in orange and green, respectively. (A) Measured FoVs of the unmagnified and magnified setups are 9100 ± 82 and 819 ± 9 μm, respectively. (B) Edge response functions fitted to the data of the two imaging arrangements. (C) Measured resolutions of the unmagnified and magnified setups are 322 ± 5 and 35 ± 5 μm, respectively. The smallest features in a resolution target that can be resolved for each arrangement are presented. The 10-fold magnification, resulting in the scaling of the resolution and FoV, is manifested in a narrower extend along the horizontal direction (accentuated by the green shaded rectangle in the plots). Orange scale bar corresponds to 2 mm, and green scale bar corresponds to 0.1 mm. Unmagnified (magnified) images were acquired with 1-s integration time and 200 (400)–mW pump power.

  • Fig. 3 Multispectral imaging.

    Obtained signal transmission images for varying mid-IR illumination wavelengths. Scale bar, 2 mm. The spectra were recorded at the signal wavelength with a grating spectrometer and converted to the corresponding mid-IR wavelength.

  • Fig. 4 Bioimaging.

    Histology sample of a mouse heart with (A) bright-field microscopy with visible light for illustration of the part of the sample we investigated with our method. (B and C) Mid-IR microscopy of the same sample with undetected photons for absorption (B) and phase (C) imaging. Scale bar, 200 μm. Images were reconstructed by averaging 10 images at 1-s integration time for 15 axial positions within the coherence length of the biphoton. Pump power was 400 mW corresponding to a sample illumination power of less than 20 pW.

Supplementary Materials

  • Supplementary Materials

    Microscopy with undetected photons in the mid-infrared

    Inna Kviatkovsky, Helen M. Chrzanowski, Ellen G. Avery, Hendrik Bartolomaeus, Sven Ramelow

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