  The emerging technique of mid-infrared optical coherence tomography (MIR-OCT)
takes advantage of the reduced scattering of MIR light in various materials and
devices, enabling tomographic imaging at deeper penetration depths. Because of
challenges in MIR detection technology, the image acquisition time is however
significantly longer than for tomographic imaging methods in the
visible/near-infrared. Here we demonstrate an alternative approach to MIR
tomography with high-speed imaging capabilities. Through femtosecond
non-degenerate two-photon absorption of MIR light in a conventional Si-based
CCD camera, we achieve wide-field, high-definition tomographic imaging with
chemical selectivity of structured materials and biological samples in mere
seconds.
