Infrared Two-Color Ghost Imaging Using Entangled Beams

We carried out ghost imaging experiments using nondegenerate entangled beams with the central wavelengths at 810 nm and 1550 nm. The pulsed pump at 532 nm had the high efficiency of parametric down conversion and enabled ghost imaging although its average pump power was 10 mW. For the first time, we demonstrated ghost imaging with two disparate detectors: Si avalanche photodiode on one arm and InGaAs avalanche photodiode on the other. Objects were placed in the arm of the 1550 nm beam, whereas the imaging lens was placed in the arm of the 810 nm beam. Ghost imaging was constructed by using the quantum correlated portion of the data due to the nature of the entangled beams. Current theory for this configuration predicted that the image magnification by a degenerate source should be one and half times larger than that of this nondegenerate source; the observed magnification followed closely the value predicted by the theory.