Classical Imaging with Undetected Light

TL;DR

This paper demonstrates a classical imaging technique that captures phase and intensity images of an object using light that never directly interacts with it, leveraging stimulated parametric down conversion and interference of idler beams.

Contribution

It introduces a novel classical imaging method that reproduces quantum-like imaging capabilities without requiring quantum entanglement.

Findings

High contrast images achieved with low transmittance objects

Imaging performed with light that does not interact with the object

Method applicable for wavelengths lacking suitable detectors

Abstract

We obtained the phase and intensity images of an object by detecting classical light which never interacted with it. With a double passage of a pump and a signal laser beams through a nonlinear crystal, we observe interference between the two idler beams produced by stimulated parametric down conversion. The object is placed in the amplified signal beam after its first passage through the crystal, and the image is observed in the interference of the generated idler beams. High contrast images can be obtained even for objects with small transmittance coefficient due to the geometry of the interferometer and to the stimulated parametric emission. Like its quantum counterpart, this three-colour imaging concept can be useful when the object must be probed with light at a wavelength for which detectors are not available.