  We demonstrate optical coherence tomography based on an SU(1,1) nonlinear
interferometer with high-gain parametric down-conversion. For imaging and
sensing applications, this scheme promises to outperform previous experiments
working at low parametric gain, since higher photon fluxes provide lower
integration times for obtaining high-quality images. In this way one can avoid
using single-photon detectors or CCD cameras with very high sensitivities, and
standard spectrometers can be used instead. Other advantages are: higher
sensitivity to small loss and amplification before detection, so that the
detected light power considerably exceeds the probing one.
