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Paper: Electro-Optics of an Experimental Quantum-Optical Photometer
Volume: 424, Proceedings of the 9th International Conference of the Hellenic Astronomical Society
Page: 446
Authors: Solomos, N. H.
Abstract: The first working version of a new ultrafast three-beam photon counting photometer (QOP) has been materialized and demonstrated by the Applied Physics / Electro-optics Laboratory of the Hellenic Naval Academy in Piraeus. The QOP has been installed on the new 0.51m TVD telescope. The instrument is currently being used for quantum-optical study of atmospheric transmission in green monochromatic light over slant paths, at the RFK/Eudoxos Observatories. Actively quenched Single Photon Avalanche Diode detectors can be interchangeably deployed in addition to PMTs and LLL-CCDs. It is also intended for the testing of various approaches for solving the difficult problem of coupling light efficiently to the very small sensitive areas of SPADS, either using fiber couplers, or novel technologies like dedicated fiber tapers. Some particulars of the instrument design philosophy and its optomechanical construction are very briefly mentioned further below. However, it is appropriate to comment, firstly, on its purpose/rationale: The successful formalism of Glauber that led to the quantum-optical framework pertinent to the study of light in the terrestrial laboratories could, perhaps, be proven equally fruitful if applied to celestial light as well. Adopting the new idea of describing an arbitrary light state in terms of coherence functions, it is easily concluded that conventional astronomical instrumentation measures only spatial (imaging) or temporal (spectroscopy) coherence properties of the incoming photon stream. However, higher order spatiotemporal coherence (manifested as correlations among separated photon detection events) convey blueprints of the emission mechanism itself or even of the photon scattering history written in the course of the long path from the emitter to the telescope. To extract this information, high photon fluxes and unprecedented timing resolutions are needed. Our gradual entrance to the era of Extremely Large Telescopes combined with certain new technological advances on the detectors and speed of signal processing, make such prospects more feasible than before. These ideas were developed in a conceptual study of a focal plane instrument (QuantEYE) for the abandoned 100 m Overwhelmingly Large Telescope of the European Southern Observatory. QuantEYE would be a novel astronomical photometer capable to push the time tagging capabilities toward the pico-second region. Barbieri et al (2006) built a proof-of-concept prototype of QuantEYE for the Asiago 182 cm telescope (AquEYE), to be followed by a larger instrument for existing 8-10 m telescopes. This paper expounds the adopted technological solutions and the first steps performed to develop another such a prototype/precursor. In seeking to experiment with an instrument capable not to extract the signal from noise but instead to treat photon-noise as its signal, we launched (1999) our own program for the development of a Greek experimental 2nd generation instrument for Q.Ap. studies in the 3D photon gas stream. The device, to be called quantum-chrono-phasmatometer (KB.X), was of the quantum-spectrometer type. Some particular initial considerations regarding our exploratory approach to the design of such non-classical systems were given elsewhere (Solomos, 2006). KB.X was not implemented due to the lack of funding sources to support R&D on optical photocathodes for gaseous detectors. Instead, a less demanding second variant named QOP has been realized, for the purpose of experimentation in facilitating statistical characterization studies of the atmospheric channel associated with very high time resolution.
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