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Tisa S.,Micro Photon Devices Srl | Villa F.,Polytechnic of Milan | Giudice A.,Micro Photon Devices Srl | Simmerle G.,Micro Photon Devices Srl | Zappa F.,Polytechnic of Milan
IEEE Journal on Selected Topics in Quantum Electronics | Year: 2015

Optical quantum random number generators (QRNGs) are a special class of physical random data sources, whose randomness is established on elementary quantum optics processes. We present a QRNG based on a CMOS chip which overcomes the limitations of the commonly used optical QRNG and which achieves a random bit generation rate up to 200 Mb/s. The CMOS chip is based on an array of single-photon avalanche diodes (SPADs) and digital counters. We prove the absolute randomness of the generated random data through statistical test suites and even more stringent correlation and bias tests applied to 32 Gbit streams. The QRNG passes all tests; hence, it proves to be one of the fastest and more reliable CMOS optical QRNGs currently available. © 2014 IEEE.

Tosi A.,Polytechnic of Milan | Mora A.D.,Polytechnic of Milan | Zappa F.,Polytechnic of Milan | Zappa F.,Micro Photon Devices Srl | And 8 more authors.
Optics Express | Year: 2011

In many time-domain single-photon measurements, wide dynamic range (more than 5 orders of magnitude) is required in short acquisition time (few seconds). We report on the results of a novel technique based on a time-gated Single-Photon Avalanche Diode (SPAD) able to increase the dynamic range of optical investigations. The optical signal is acquired only in well-defined time intervals. Very fast 200-ps gate-ON transition is used to avoid the undesired strong signal, which can saturate the detector, hide the fainter useful signal and reduce the dynamic range. In experimental measurements, we obtained a dynamic range approaching 8 decades in few minutes of acquisition. © 2011 Optical Society of America.

Cammi C.,Polytechnic of Milan | Panzeri F.,Polytechnic of Milan | Gulinatti A.,Polytechnic of Milan | Rech I.,Polytechnic of Milan | And 2 more authors.
Review of Scientific Instruments | Year: 2012

Emerged as a solid state alternative to photo multiplier tubes (PMTs), single-photon avalanche diodes (SPADs) are nowadays widely used in the field of single-photon timing applications. Custom technology SPADs assure remarkable performance, in particular a 10 counts/s dark count rate (DCR) at low temperature, a high photon detection efficiency (PDE) with a 50 peak at 550 nm and a 30 ps (full width at half maximum, FWHM) temporal resolution, even with large area devices, have been obtained. Over the past few years, the birth of novel techniques of analysis has led to the parallelization of the measurement systems and to a consequent increasing demand for the development of monolithic arrays of detectors. Unfortunately, the implementation of a multidimensional system is a challenging task from the electrical point of view; in particular, the avalanche current pick-up circuit, used to obtain the previously reported performance, has to be modified in order to enable high parallel temporal resolution, while minimizing the electrical crosstalk probability between channels. In the past, the problem has been solved by integrating the front-end electronics next to the photodetector, in order to reduce the parasitic capacitances and consequently the filtering action on the current signal of the SPAD, leading to an improvement of the timing jitter at higher threshold. This solution has been implemented by using standard complementary metal-oxide-semiconductor (CMOS) technologies, which, however, do not allow a complete control on the SPAD structure; for this reason the intrinsic performance of CMOS SPADs, such as DCR, PDE, and afterpulsing probability, are worse than those attainable with custom detectors. In this paper, we propose a pixel architecture, which enables the development of custom SPAD arrays in which every channel maintains the performance of the best single photodetector. The system relies on the integration of the timing signal pick-up circuit next to the photodiode, achieved by modifying the technological process flow used for the fabrication of the custom SPAD. The pixel is completed by an external standard CMOS active quenching circuit, which assures stable timing performance at quite high count rate (1 MHz). © 2012 American Institute of Physics.

Cuccato A.,Polytechnic of Milan | Antonioli S.,Polytechnic of Milan | Crotti M.,Polytechnic of Milan | Labanca I.,Polytechnic of Milan | And 4 more authors.
IEEE Photonics Journal | Year: 2013

Single-photon detectors play a key role in many research fields such as biology, chemistry, medicine, and space technology, and in recent years, single-photon avalanche diodes (SPADs) have become a valid alternative to photo multiplier tubes (PMTs). Moreover, scientific research has recently focused on single-photon detector arrays, pushed by a growing demand for multichannel systems. In this scenario, we developed a compact 32-channel system for time-resolved single-photon counting applications. The system is divided into two independent modules: a photon detection head including a 32 \times 1 SPAD array built in custom technology, featuring high time resolution, high photon detection efficiency (44% at 550 nm), and low dark count rate (mean value 400 cps at -10\ ^{\circ}\hbox{C}) at 6-V excess bias voltage and a 32-channel acquisition system able to perform time-correlated single-photon counting (TCSPC) measurements. The TCSPC module includes eight four-channel time-to-amplitude converter (TAC) arrays, built-in 0.35-\mum Si-Ge BiCMOS technology, characterized by low differential non-linearity (rms value lower than 0.15% of the time bin width) and variable full-scale range. The system response function of this TCSPC instrumentation achieves a mean time resolution of 63 ps\rm FWHM, considering a mean count rate of 1 Mcps. © 2009-2012 IEEE.

Markovic B.,Polytechnic of Milan | Tisa S.,Micro Photon Devices Srl | Tosi A.,Polytechnic of Milan | Zappa F.,Polytechnic of Milan
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2011

We present a novel "smart-pixel" able to measure and record in-pixel the time delay (photon timing) between a START (e.g. given by laser excitation, cell stimulus, or LIDAR flash) and a STOP (e.g. arrival of the first returning photon from the fluorescence decay signal or back reflection from an object). Such smart-pixel relies of a SPAD detector and a Time-to-Digital Converter monolithically designed and manufactured in the same chip. Many pixels can be laid out in a rows by columns architecture, to give birth to expandable 2D imaging arrays for picoseconds-level single-photon timing applications. Distance measurements, by means of direct TOF detection (used in LIDAR systems) provided by each pixel, can open the way to the fabrication of single-chip 3D ranging arrays for scene reconstruction and intelligent object recognition. We report on the design and characterization of prototype circuits, fabricated in a 0.35μm standard CMOS technology containing complete conversion channels, "smart-pixel" and ancillary electronics with 20 μm active area diameter SPAD detector and related quenching circuitry. With a 100 MHz reference clock, the TDC provides time-resolution of 10 ps, dynamic range of 160 ns and very high conversion linearity.

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