Ghost Imaging with Sunlight
Creators: name: Karmakar, Sanjit
Publisher: name: Maryland Shared Open Access Repository
Year: 2012
Subjects: Ghost Imaging with sunlight
two-color ghost imaging
two-photon interference

description: The main result of this dissertation is the first successful experimental demonstration of ghost imaging using the sun as a light source. This result supports the quantum theory of near-field thermal light ghost imaging and also clarifies the physics of near-field thermal light ghost imaging from the fundamental level. The quantum theory of two-photon interference is the key to understanding the nonlocal ghost imaging with thermal light sources. Two-photon interference occurs between two different yet indistinguishable probability two-photon amplitudes, nonclassical entities produced by the joint-detection between two distant photodetectors. An experimental study of nontrivial spatial correlation and nontrivial anti-correlation from a pulsed chaotic-thermal source is also reported briefly in this dissertation to understand the two-photon interference phenomenon in case of classical thermal light. On the other hand, the classical theory considers thermal light ghost imaging to be the result of intensity fluctuation correlation. Interestingly, the physicists who believe in intensity fluctuation correlation was misled by the speckle-to-speckle picture. The successful experimental demonstration of ghost imaging with sunlight suggests that the nonlocal ghost-imaging effect of thermal light is caused by quantum-mechanical two-photon interference and it also proves that the idea of speckles is unnecessary in near-field thermal light ghost imaging. Most importantly, sunlight does not have any speckle and the sun is a near-field source. The experimental studies on sunlight-based ghost imaging are discussed in two steps: (1) an experimental demonstration as well as a quantum mechanical explanation of the nontrivial intensity correlation with the sun, a natural thermal source, as a light source and (2) the demonstration of the experimental observation of ghost imaging with sunlight with its quantum-mechanical explanation. These observations with their theoretical explanation are very helpful to understanding the physics of ghost imaging from a fundamental level. From the application point of view, sunlight-based ghost imaging may achieve a spatial resolution equivalent to that of a classical imaging system taking pictures at a distance of 10 km with a lens of 92 m size. This dissertation also reports an experimental demonstration on two-color, biphoton ghost imaging which reproduced a ghost image with enhanced angular resolving power by means of a greater field of view compared with that of classical imaging. With the same imaging magnification, the enhanced angular resolving power and field of view compared with that of classical imaging are 1.25 : 1 and 1.16 : 1 respectively. The enhancement of angular resolving power depends on the ratio between the idler and the signal photon frequencies and the enhancement of the field of view depends mainly on the same ratio and also on the distances of the object plane and the imaging lens from the two-photon source. A greater field of view under the enhanced resolving  power of an imaging system is a useful and important feature in certain applications. We also report the possibility of reproducing a ghost image with the enhancement of the angular resolving power by means of a greater imaging amplification compared with that of classical imaging. In certain applications, a greater imaging amplification with enhanced resolving power of an imaging system is a useful and important feature. Until now ghost imaging using thermal light with only one color is experimentally demonstrated. A way to achieve sunlight-based ghost imaging with real colors (i.e., multiple colors) is proposed in this dissertation. The experience gained in two-color ghost imaging experiment with entangled photon pairs will be helpful to get a real color ghost image with sunlight. Potential real color sunlight-based ghost imaging with its nonlocal behavior and turbulence-free nature gives us a promise for its applications in distant imaging.