  We demonstrate a different scheme to perform optical sectioning of a sample
based on the concept of induced coherence [Zou et al., Phys. Rev. Lett. 67, 318
(1991)]. This can be viewed as a different type of optical coherence tomography
scheme where the varying reflectivity of the sample along the direction of
propagation of an optical beam translates into changes of the degree of
first-order coherence between two beams. As a practical advantage the scheme
allows probing the sample with one wavelength and measuring photons with
another wavelength. In a bio-imaging scenario, this would result in a deeper
penetration into the sample because of probing with longer wavelengths, while
still using the optimum wavelength for detection. The scheme proposed here
could achieve submicron axial resolution by making use of nonlinear parametric
sources with broad spectral bandwidth emission.
