1,721,018 research outputs found
Low-cost and compact single-photon counter based on a CMOS SPAD smart pixel
Full text linkWe present a single-photon counter based on a silicon Single-Photon Avalanche Diode (SPAD) fabricated in a 0.35 μm CMOS technology. The detector is monolithically integrated with a front-end circuit and a digital pulse output driver. External components are kept to a minimum and the resulting instrument is low-cost, low-power and compact, being housed into an industry-standard 1-inch aluminum optical mounting tube. It features a maximum power consumption of just 250 mW from an USB link. The embedded 50 μm diameter SPAD has high photon detection efficiency in the visible range (55 % at 420 nm), low noise (< 100 cps at room temperature), low timing jitter (< 100 ps full-width at half maximum), and very low afterpulsing probability (down to 1 % with 60 ns hold-off time). The high performance, compactness and low cost enable many unexplored applications in life sciences, personal health care, industrial quality check, quantum physics and others, where it is required to count single photons and to measure their arrival time
InGaAs/InP single-photon detector gated at 1.3 GHz with 1.5% afterpulsing
Full text linkWe demonstrate a single-photon detector based on InGaAs/InP single-photon avalanche diodes (SPADs) sinusoidalgated at 1.3 GHz with very low afterpulsing (about 1.5%), high dynamic range (maximum count rate is 650 Mcount/s), high photon detection efficiency (>30% at 1550 nm), low noise (per-gate dark count rate is 2.2 x 10(-5)), and low timing jitter (<70 ps full-width at half-maximum). The SPAD is paired with a "dummy" structure that is biased in antiphase. The sinusoidal gating signals are cancelled by means of a common-cathode configuration and by adjusting the relative amplitude and phase of the signals biasing the two arms. This configuration allows us to adjust the gating frequency from 1 to 1.4 GHz and can be operated also in the so-called gate-free mode, with the gate sine-wave unlocked with respect to the light stimulus, resulting in a free-running equivalent operation of the InGaAs/InP SPAD with about 4% average photon detection efficiency at 1550 nm
Fast-gating of single-photon avalanche diodes with 200 ps transitions and 30 ps timing jitter
No full textWe present circuits and methods for fast-gating a silicon Single-Photon Avalanche Diode (SPAD) in order to attain wide dynamic range in the measurement of very faint and very fast optical signals. A mixed-signal amplifier comprising ECL logic and microwave components allows to achieve turn-ON and turn-OFF transition times below 200 ps and gating windows from 10 ns down to just few hundreds of picoseconds. A differential front-end electronics reads out the avalanche current pulse while rejecting spurious spikes due to the gate pulse, thus achieving a photon detection timing jitter below 30 ps. This paper describes the conceived circuit solutions, the overall instrument development and the results of its characterization and validation
High-throughput gated photon counter with two detection windows programmable down to 70 ps width
Full text linkWe present the design and characterization of a high-throughput gated photon counter able to count electrical pulses occurring within two well-defined and programmable detection windows. We extensively characterized and validated this instrument up to 100 Mcounts/s and with detection window width down to 70 ps. This instrument is suitable for many applications and proves to be a cost-effective and compact alternative to time-correlated single-photon counting equipment, thanks to its easy configurability, user-friendly interface, and fully adjustable settings via a Universal Serial Bus (USB) link to a remote computer
Fast-gated single-photon detector module for wide dynamic range optical measurements
No full textWe present an innovative instrument based on a time-gated silicon Single-Photon Avalanche Diode (SPAD) to be used in a Time-Correlated Single-Photon Counting (TCSPC) setup. This instrument is able to increase the dynamic range in optical investigations by means of fast transitions between the OFF and the ON state of the detector. Indeed, an ultra-fast pulse generator embedded in the module allows to enable and disable the detector in less than 200 ps for very short and well-defined time slots. The present technique can be employed when a large amount of undesired photons precedes or follows the optical signal to be measured, such as in time-resolved optical spectroscopy, optical mammography and optical molecular imaging. Thanks to the fast-gating technique it is possible to drastically extend the dynamic range of single-photon optical measurements with short integration times
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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