AquEYE, a single photon counting photometer for astronomy

Abstract

This paper describes the results obtained so far with AquEYE, a single photon counting, fixed aperture photometer for the Asiago 182 cm telescope. AquEYE has been conceived as a prototype of a truly ‘quantum’ photometer for future Extremely Large Telescopes of 30–50 m aperture. This prototype is characterized by four independent channels equipped with single photon avalanche diodes (SPADs) as detectors. The counts from the four channels are acquired by a TDC board which has a nominal 25 ps time tagging capability. Taking into account the 35 ps jitter in the SPAD itself, the overall precision of the time tags is of the order of 50 ps. The internal oscillator is locked to an external rubidium clock; a GPS pulse per second is collected by the TDC itself to obtain a UTC reference. The maximum photon count rate which the present system can sustain is 12 MHz

Aqueye+: a new ultrafast single photon counter for optical high time resolution astrophysics

“…Aqueye and Iqueye ( Figure 1) are the prototypes for a quantum photometer for the future 40 m class telescopes such as the E-ELT 10 and represent the world recognized leading astronomical instruments for the shortest time scales in the optical band 6,7 . They couple the ultra-high time resolution of SPAD detectors with a split-pupil optical concept and a sophisticated timing system.…”

“…We pioneered the use of Geiger-mode Single Photon Avalanche Photodiodes (SPAD) building Aqueye for the Asiago 1.8 m Copernico telescope 6 and Iqueye for the ESO 3.6 m New Technology Telescope (NTT) 7 . SPADs are, at present, the photon counting detectors with the best timing performance, 30-50 ps time resolution, 10-100 dark counts/s, 6-8 MHz maximum count rate, visible quantum efficiency up to 60% 8,9 .…”

“…Inside the instrument the light beam crosses a focal reducer, where optical elements can be inserted through suitable filter wheels, and is then split in 4 symmetrical arms by a pyramidal mirror 6,7,11 ( Figure 2). In each arm, additional filters and polarizers can be inserted in a collimated portion of the beam.…”

“…The signal from the SPADs is sent to a Time To Digital Converter (TDC) board, made by CAEN (Costruzioni Apparecchiature Elettroniche Nucleari, Italy), and then to a dedicated acquisition server 6,7,11 ( Figure 3). The TDC makes use of an external Rubidium clock and a GPS unit for checking the long time stability of the clock.…”

Alignment position method for SPAD detector calibration and homogeneity

“…1,2 In particular, Si-SPADs have been successfully exploited in a variety of scientific research fields such as experimental quantum optics, quantum cryptography and quantum computing but also in applications like medicine, biology, 3D imaging, telecommunication and astrophysics. [3][4][5] In all these fields, the detection efficiency is a key parameter. Nevertheless, most of the costumers have to rely on the detection efficiency values given by the manufacturers or they have to measure the values themselves.…”