Very fast photon counting photometers for astronomical applications: from QuantEYE to AquEYE

In the great majority of the cases, present astronomical observations are realized analyzing only first order spatial or temporal coherence properties of the collected photon stream. However, a lot of information is “hidden” in the second and higher order coherence terms, as details about a possible stimulated emission mechanism or about photon scattering along the travel from the emitter to the telescope. The Extremely Large Telescopes of the future could provide the high photon flux needed to extract this information. To this aim we have recently studied a possible focal plane instrument, named QuantEYE, for the 100 m OverWhelmingly Large Telescope of the European Southern Observatory. This instrument is the fastest photon counting photometer ever conceived, with an array of 100 parallel channels operating simultaneously, to push the time tagging capabilities toward the pico-second region. To acquire some experience with this novel type of instrumentation, we are now in the process of realizing a small instrument prototype (AquEYE) for the Asiago 182 cm telescope, for then building a larger instrument for one of the existing 8-10 m class telescopes. We hope that the results we will obtain by these instruments will open a new frontier in the astronomical observations.