Possible applications of a novel type of photon counting instrument for Intensity Interferometry observations Intensity Interferometry observations Giampiero Naletto University of Padova Workshop on Stellar Intensity Interferometry p y y Salt Lake City 29 ‐ 30 January 2009
Introduction During the last years we realized in Padova two similar instruments, AquEYE and IquEYE, for astronomical applications . They are essentially extremely fast photon counters, with the capability of time tagging the collected photons with a 50 ps time accuracy and storing all the timing data in a mass memory. This type of instrument is really versatile because it allows to operate independently with distant telescopes if a suitable clock t i d d tl ith di t t t l if it bl l k synchronization can be obtained. We are planning to further develop this type of instruments for We are planning to further develop this type of instruments for possible applications that can range from “quantum” observations with future ELTs, as measurement of second and , higher order correlation functions from remote light sources, to intensity interferometry with existing telescopes as VLT and Keck. Giampiero Naletto Possible applications of a novel type of photon counting 2 SLC Workshop on SII astronomical instrument for Intensity Interferometry observations
The team Many people are participating to the realization of this project: realization of this project: Univ. Padova: C. Barbieri, I. Capraro, G. Naletto, T. Occhipinti, E. Verroi, P. , p , , Zoccarato, V. Da Deppo, C. Facchinetti, C. Germanà, E. Giro, M. Parrozzani, F. Tamburini, M. Zaccariotto, L. Zampieri INAF Rome: A. Di Paola, INAF R A Di P l INAF Cagliari: P. Bolli, C. Pernechele INAF Catania: S. Billotta, G. Bonanno, ll Collaborations: D. Dravins (Lund), A. C d Cadez (Ljubljana) (Lj blj ) Giampiero Naletto Possible applications of a novel type of photon counting 3 SLC Workshop on SII astronomical instrument for Intensity Interferometry observations
Outline • Some history: QuantEYE • Some history: QuantEYE • Description of AquEYE and of some of the obtained results • Description of Iq EYE and of some of the obtained res lts • Description of IquEYE and of some of the obtained results (very preliminary) • Results of the Joint Asiago Ljubljana Crab pulsar observation • Results of the Joint Asiago ‐ Ljubljana Crab pulsar observation (preliminary) • Instrument present limitations and possible ways to overcome Instrument present limitations and possible ways to overcome them • Future applications pp Giampiero Naletto Possible applications of a novel type of photon counting 4 SLC Workshop on SII astronomical instrument for Intensity Interferometry observations
QuantEYE proposal In Sept. 2005, we completed a study (QuantEYE, the ESO Quantum Eye) in the frame of the studies for the 100 m OWL telescope. The main goal of the study was to demonstrate the possibility to reach the ps time resolution needed to bring the ps time resolution needed to bring quantum optics concepts into the astronomical domain, with two main , scientific aims in mind: ‐ Measure the entropy of the light through the statistics of the photon time of arrival (TOA) ‐ Demonstrate the feasibility of HBTII Giampiero Naletto Possible applications of a novel type of photon counting 5 SLC Workshop on SII astronomical instrument for Intensity Interferometry observations
Why studying the photon time statistics ? Giampiero Naletto Possible applications of a novel type of photon counting 6 SLC Workshop on SII astronomical instrument for Intensity Interferometry observations
Why Extremely Large Telescopes? The above mentioned quantum correlations are fully developed on time scales of the order of the inverse optical bandwidth For on time scales of the order of the inverse optical bandwidth. For instance, with the very narrow band pass Δλ = 0.1 nm in the visible, through a definite polarization state, typical time scales are 10 ps. However, the photon flux is very weak even from bright stars, so that only Extremely that only Extremely Large Telescopes (ELTs) can bring Quantum g Q Optical effects in the astronomical reaches. Giampiero Naletto Possible applications of a novel type of photon counting 7 SLC Workshop on SII astronomical instrument for Intensity Interferometry observations
QuantEYE QuantEYE was conceived for measuring second ‐ and higher ‐ order correlation functions in the collected photon stream (up to 1 GHz) from OWL with the highest time resolution (better than 0 1 ns) time resolution (better than 0.1 ns). Giampiero Naletto Possible applications of a novel type of photon counting 8 SLC Workshop on SII astronomical instrument for Intensity Interferometry observations
Key limitation: the detector The most critical point, and driver for the possible optical designs of QuantEYE was the availability of very fast and accurate of QuantEYE, was the availability of very fast and accurate photon counting detectors. • Imaging PC detectors (ICCD, ICMOS, MCP) either do not allow g g ( , , ) fast time tagging of the detected events, or have a rather low maximum total count rate • Non ‐ imaging PC detectors (PMT, SPADs) either have a relatively low QE, or have a small sensitive area SPADs are preferable: a 50 ps time resolution with count rates as high as 10 MHz can be obtained, with standard voltages and QE. However, even if the time resolution could be acceptable for this f h l ld b bl f h application, the total count rate was still two orders of magnitude smaller than what was necessary ! magnitude smaller than what was necessary ! Giampiero Naletto Possible applications of a novel type of photon counting 9 SLC Workshop on SII astronomical instrument for Intensity Interferometry observations
Solution: splitting the problems … To suitably design the system and to overcome both the SPAD limitations and the difficulties of a reasonable optical design limitations and the difficulties of a reasonable optical design (coupling the 100 m pupil / 600 m focal length of OWL with a single 50 μ m detector !), we decided to split the problems . In practice, we designed QuantEYE subdividing the system pupil into N × N sub ‐ pupils, each of them focused on a single SPAD (so giving a total of N 2 distributed SPAD's). In such a way, a “sparse” SPAD array (SSPADA) coping with the required very high count rate could be obtained. i d hi h ld b b i d The SSPADA is sampling the telescope pupil, so a system of N 2 parallel smaller telescopes is realized each one acting as a fast parallel smaller telescopes is realized, each one acting as a fast photometer. Giampiero Naletto Possible applications of a novel type of photon counting 10 SLC Workshop on SII astronomical instrument for Intensity Interferometry observations
QuantEYE optical design Schematic view of the telescope pupil subdivision Giampiero Naletto Possible applications of a novel type of photon counting 11 SLC Workshop on SII astronomical instrument for Intensity Interferometry observations
Advantages of this optical design • The global count rate is statistically increased by a factor N 2 N 2 Th l b l t t i t ti ti ll i d b f t with respect to the maximum count rate of a single SPAD. In the assumption of having N = 10 (100 SPAD's), the global count the assumption of having N 10 (100 SPAD s), the global count rate becomes 1 GHz (one photon every 100 ns on each SPAD) • Simpler optical design Simpler optical design • Detector redundancy • By suitable cross correlations of the detected signal a digital • By suitable cross ‐ correlations of the detected signal, a digital HBT intensity interferometer is realized among a large number of different sub ‐ apertures across the full OWL pupil p p p Giampiero Naletto Possible applications of a novel type of photon counting 12 SLC Workshop on SII astronomical instrument for Intensity Interferometry observations
Overall QuantEYE block diagram The overall system: two heads controls storage time unit The overall system: two heads, controls, storage, time unit. Giampiero Naletto Possible applications of a novel type of photon counting 13 SLC Workshop on SII astronomical instrument for Intensity Interferometry observations
AquEYE While expecting the realization of the future E ‐ ELT we decided of the future E ELT, we decided to apply the described concept to realize a much smaller version of the instrument, compatibly also with the f few available funds. il bl f d We named this instrument AquEYE the Asiago quantum AquEYE, the Asiago quantum eye: it has been applied to the AFOSC camera of the Asiago ‐ Cima Ekar (Italy) 182 cm Telescope. Giampiero Naletto Possible applications of a novel type of photon counting 14 SLC Workshop on SII astronomical instrument for Intensity Interferometry observations
AquEYE optomechanical design A simple way of realizing this small prototype was to consider an optical configuration in which the telescope pupil is divided in optical configuration in which the telescope pupil is divided in four parts only by means of a pyramidal mirror. Giampiero Naletto Possible applications of a novel type of photon counting 15 SLC Workshop on SII astronomical instrument for Intensity Interferometry observations
AquEYE subsystems AFOSC focus AFOSC focus Pyramid y Focusing lenses g Filters SPAD Giampiero Naletto Possible applications of a novel type of photon counting 16 SLC Workshop on SII astronomical instrument for Intensity Interferometry observations
Recommend
More recommend
