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Bolzano, Italy

Vitali M.,OMICRON Energy Solutions GmbH | Bronzi D.,Polytechnic of Milan | Krmpot A.J.,University of Belgrade | Nikolic S.N.,University of Belgrade | And 8 more authors.
IEEE Journal on Selected Topics in Quantum Electronics | Year: 2014

Confocal laser scanning microscopy (CLSM) is commonly used to observe molecules of biological relevance in their native environment, the live cell, and study their spatial distribution and interactions nondestructively. CLSM can be easily extended to measure the lifetime of the excited state, the concentration and the diffusion properties of fluorescently labeled molecules, using fluorescence lifetime imaging microscopy (FLIM) and fluorescence correlation spectroscopy (FCS), respectively, in order to provide information about the local environment and the kinetics of molecular interaction in live cells. However, these parameters cannot be measured simultaneously using conventional CLSM due to damaging effects that are associated with strong illumination, including phototoxicity, photobleaching, and saturation of the fluorescence signal. To overcome these limitations, we have developed a new camera consisting of 1024 single-photon avalanche diodes that is optimized for multifocal microscopy, FLIM and FCS. We show proof-of-principle measurements of fluorescence intensity distribution and lifetime of the enhanced green fluorescent protein expressed in live cells and measurement of quantum dot diffusion in solution by FCS using the same detector. © 1995-2012 IEEE. Source

Villa F.,Polytechnic of Milan | Lussana R.,Polytechnic of Milan | Bronzi D.,Polytechnic of Milan | Tisa S.,Micro Photon Device SRL | And 7 more authors.
IEEE Journal on Selected Topics in Quantum Electronics | Year: 2014

We present a CMOS imager consisting of 32 × 32 smart pixels, each one able to detect single photons in the 300. 900 nm wavelength range and to perform both photon-counting and photon-timing operations on very fast optical events with faint intensities. In photon-counting mode, the imager provides photonnumber (i.e., intensity) resolvedmovies of the scene under observation, up to 100 000 frames/s. In photon-timing, the imager provides photon arrival times with 312 ps resolution. The result are videos with either time-resolved (e.g., fluorescence) maps of a sample, or 3-D depth-resolvedmaps of a target scene. The imager is fabricated in a cost-effective 0.35-μm CMOS technology, automotive certified. Each pixel consists of a single-photon avalanche diode with 30 μm photoactive diameter, coupled to an in-pixel 10-bit time-to-digital converter with 320-ns full-scale range, an INL of 10% LSB and a DNL of 2% LSB. The chip operates in global shutter mode, with full frame times down to 10 μs and just 1-ns conversion time. The reconfigurable imager design enables a broad set of applications, like time-resolved spectroscopy, fluorescence lifetime imaging, diffusive optical tomography, molecular imaging, time-of-flight 3-D ranging and atmospheric layer sensing through LIDAR. © 2014 IEEE. Source

Bronzi D.,Polytechnic of Milan | Villa F.,Polytechnic of Milan | Bellisai S.,Polytechnic of Milan | Tisa S.,Micro Photon Device SRL | And 2 more authors.
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2013

SPADs (Single Photon Avalanche Diodes) are emerging as most suitable photodetectors for both single-photon counting (Fluorescence Correlation Spectroscopy, Lock-in 3D Ranging) and single-photon timing (Lidar, Fluorescence Lifetime Imaging, Diffuse Optical Imaging) applications. Different complementary metal-oxide semiconductor (CMOS) implementations have been reported in literature. We present some figure of merit able to summarize the typical SPAD performances (i.e. Dark Counting Rate, Photo Detection Efficiency, afterpulsing probability, hold-off time, timing jitter) and to identify a proper metric for SPAD comparison, both as single detectors and also as imaging arrays. The goal is to define a practical framework within which it is possible to rank detectors based on their performances in specific experimental conditions, for either photon-counting or photon-timing applications. Furthermore we review the performances of some CMOS and custom-made SPADs. Results show that CMOS SPADs performances improve as the technology scales down; moreover, miniaturization of SPADs and new solutions adopted to counteract issues related with the SPAD design (electric field uniformity, premature edge breakdown, tunneling effects, defect-rich STI interface) along with advances in standard CMOS processes led to a general improvement in all fabricated photodetectors; therefore, CMOS SPADs can be suitable for very dense and cost-effective many-pixels imagers with high performances. © 2013 SPIE. Source

Zou Y.,Polytechnic of Milan | Villa F.,Polytechnic of Milan | Bronzi D.,Polytechnic of Milan | Tisa S.,Micro Photon Device SRL | And 2 more authors.
Journal of Modern Optics | Year: 2015

Silicon photomultipliers (SiPMs) are large area detectors consisting of an array of single-photon-sensitive microcells, which make SiPMs extremely attractive to substitute the photomultiplier tubes in many applications. We present the design, fabrication, and characterization of analog SiPMs in standard planar 0.35 m CMOS technology, with about 1 mm × 1 mm total area and different kinds of microcells, based on single-photon avalanche diodes with 30 m diameter reaching 21.0% fill-factor (FF), 50 m diameter (FF = 58.3%) or 50 m square active area with rounded corner of 5 m radius (FF = 73.7%). We also developed the electrical SPICE model for CMOS SiPMs. Our CMOS SiPMs have 25 V breakdown voltage, in line with most commercial SiPMs and higher gain (8.8 × 106, 13.2 × 106, and 15.0 × 106, respectively). Although dark count rate density is slightly higher than state-of-the-art analog SiPMs, the proposed standard CMOS processing opens the feasibility of integration with active electronics, for switching hot pixels off, drastically reducing the overall dark count rate, or for further on-chip processing. © 2015 Taylor and Francis. Source

Villa F.,Polytechnic of Milan | Markovic B.,Polytechnic of Milan | Bellisai S.,Polytechnic of Milan | Bronzi D.,Polytechnic of Milan | And 7 more authors.
IEEE Photonics Journal | Year: 2012

We present a smart pixel based on a single-photon avalanche diode (SPAD) for advanced time-of-flight (TOF) and time-correlated single photon counting (TCSPC) applications, fabricated in a cost-effective 0.35-μ CMOS technology. The large CMOS detector (30-μ active area diameter) shows very low noise (12 counts per second at room temperature at 5-V excess bias) and high efficiency in a wide wavelength range (about 50% at 410 nm and still 5% at 800 nm). The analog front-end electronics promptly senses and quenches the avalanche, thus leading to an almost negligible afterpulsing effect. The in-pixel 10-bit time-to-digital converter (TDC) provides 312-ps resolution and 320-ns full-scale range (FSR), i.e., 10-cm single-shot spatial resolution within 50-m depth range in a TOF system. The in-pixel 10-bit memory and output buffers make this smart pixel the viable building block for advanced single-photon imager arrays for 3-D depth ranging in safety and security applications and for 2-D fluorescence lifetime decays in biomedical imaging. © 2012 IEEE. Source

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