Proceedings Article | 21 September 2011
KEYWORDS: Signal to noise ratio, Coherence (optics), Spatial light modulators, Sensors, Correlation function, Spatial resolution, Target detection, Atmospheric propagation, Turbulence, Speckle
The theory of partial coherence has a long and storied history in classical statistical optics. The vast majority
of this work addresses fields that are statistically stationary in time, hence their complex envelopes only have
phase-insensitive correlations. The quantum optics of squeezed-state generation, however, depends on nonlinear
interactions producing baseband field operators with phase-insensitive and phase-sensitive correlations. Utilizing
quantum light to enhance imaging has been a topic of considerable current interest, much of it involving biphotons,
i.e., streams of entangled-photon pairs. Biphotons have been employed for quantum versions of optical coherence
tomography, ghost imaging, holography, and lithography. However, their seemingly quantum features have been
mimicked with classical-state light, questioning wherein lies the classical-quantum boundary. We have shown,
for the case of Gaussian-state light, that this boundary is intimately connected to the theory of phase-sensitive
partial coherence. Here we present that theory, contrasting it with the familiar case of phase-insensitive partial
coherence, and use it to elucidate the classical-quantum boundary of ghost imaging. We show, both theoretically
and experimentally, that classical phase-sensitive light produces ghost images most closely mimicking those
obtained with biphotons, and we derive the spatial resolution, image contrast, and signal-to-noise ratio of a
standoff-sensing ghost imager, taking into account target-induced speckle.
