Higher-order ghost imaging with partially polarized classical light

Abstract

Visibility, signal-to-noise ratio (SNR), and contrast-to-noise ratio (CNR) are quantities that characterize the quality of the image in ghost (or correlation) imaging. The visibility in quantum and classical ghost imaging with scalar light is known to improve as the order of imaging increases. Recently also electromagnetic ghost imaging has started to attract attention. In this work we analyze the effects of both the order of imaging and the degree of polarization (P) of the illumination on the image quality parameters. The source is a classical, partially polarized, random electromagnetic field obeying Gaussian statistics. The beam is split into several (N) parts which are directed either into the object or reference arms and the associated intensity correlations are calculated. When N > 2, more than one reference arm may exist which contributes to the background. We consider two different definitions for the visibility, as well as the SNR and CNR, and examine their attainable limiting values in second- and higher-order ghost imaging as a function of the degree of polarization. Both expressions of the visibility behave in a similar manner; they increase with the order of imaging and the degree of polarization. In second-order imaging the SNR decreases, due to increased noise, as P increases, while the CNR remains essentially constant. We emphasize that the exact numerical values depend on the definitions used and on the number of object arms in the setup.