CMOS single-photon avalanche diodes (SPADs) have recently become an emerging imaging technology for applications requiring high sensitivity and high frame-rate in the visible and near-infrared range. However, a higher photon detection efficiency (PDE), particularly in the 700-950 nm range, is highly desirable for many growing markets, such as eye-safe three-dimensional imaging (LIDAR). In this paper, we report the design and characterization of SPADs fabricated in a 0.16 μm BCD (Bipolar-CMOS-DMOS) technology. The overall detection performance is among the best reported in the literature: 1) PDE of 60% at 500 nm wavelength and still 12% at 800 nm; 2) very low dark count rate of <; 0.2 cps/μm² (in counts per second per unit area); 3) <; 1% afterpulsing probability with 50 ns dead-time; and 4) temporal response with 30 ps full width at half-maximum and less than 50 ps diffusion tail time constant.

This letter describes the reduction of optical crosstalk by means of focused ion beam-etched trenches in InGaAs/InP single-photon avalanche diode arrays. Platinum-filled trenches have been fabricated in a linear array in order to limit the direct optical crosstalk between neighboring pixels. Experimental measurements prove that optical crosstalk has been reduced by ~60% thanks to a strong suppression of direct optical paths. An optical model is introduced in order to describe the main contributions to crosstalk and to validate measurements.

We present a novel instrument for fast-gated operation of a 50 μm CMOS SPAD (Complementary Metal-Oxide-Semiconductor Single-Photon Avalanche Diode), driven by an integrated fast-gated active quenching circuit with transition times faster than 300 ps (20-80%). The instrument is based on a custom system-in-package where the SPAD and its driving electronics are housed in a TO-8 package. The detector can be operated at repetition rates up to 160 MHz, with gate on-times as short as 500 ps, always guaranteeing a temporal response with 60 ps (FWHM) timing jitter and short exponential decay (53 ps time-constant). A dark-count rate as low as 1 cps is achieved operating the CMOS SPAD at 5 V above breakdown at a temperature of 263 K, still keeping the afterpulsing probability lower than 2%, with only 50 ns hold-off time, thanks to the fast-gating driving electronics. The instrument is housed in a compact 5 4 8 cm³ case and can be triggered by either an external or internal source. A USB link allows to adjust measurement parameters, SPAD bias voltage and operating temperature. The high re-configurability of the instrument and its state-of-the-art performance make it suitable for applications where high detection rates and low timing jitter are required

Quantum key distribution (QKD) allows secret key exchange between two users with unconditional security. For QKD to be widely deployed, low cost and compactness are crucial requirements alongside high performance. Currently, the majority of QKD systems demonstrated rely on bulk intensity and phase modulators to generate optical pulses with precisely defined amplitude and relative phase difference—i.e., to encode information as signal states and decoy states. However, these modulators are expensive and bulky, thereby limiting the compactness of QKD systems. Here, we present and experimentally demonstrate a novel optical transmitter design to overcome this disadvantage by generating intensity- and phase-tunable pulses at GHz clock speeds. Our design removes the need for bulk modulators by employing directly modulated lasers in combination with optical injection locking and coherent interference. This scheme is, therefore, well suited to miniaturization and photonic integration, and we implement a proof-of-principle QKD demonstration to highlight potential applications.

Silicon photomultipliers (SiPMs) have improved significantly over the last years and now are widely employed in many different applications. However, the custom fabrication technologies exploited for commercial SiPMs do not allow the integration of any additional electronics, e.g., on-chip readout and analog (or digital) processing circuitry. In this paper, we present the design and characterization of two microelectronics-compatible SiPMs fabricated in a 0.16 µm–BCD (Bipolar-CMOS-DMOS) technology, with 0.67 mm × 0.67 mm total area, 10 × 10 square pixels and 53% fill-factor (FF). The photon detection efficiency (PDE) surpasses 33% (FF included), with a dark-count rate (DCR) of 330 kcps. Although DCR density is worse than that of state-of-the-art SiPMs, the proposed fabrication technology enables the development of cost-effective systems-on-chip (SoC) based on SiPM detectors. Furthermore, correlated noise components, i.e., afterpulsing and optical crosstalk, and photon timing response are comparable to those of best-in-class commercial SiPMs.

We describe the design and characterization of a new InGaAs/InP Single-Photon Avalanche Diode (SPAD) for single-photon detection at 1.55 μm with high detection efficiency, low noise and low timing jitter. The design and fabrication have been optimized to reduce the defects (responsible for dark counts and afterpulsing). Zinc diffusion is a key step and we optimized the profile, pattern and reactor parameters to achieve uniform sensitivity in the active area, low noise and low timing jitter. The active area diameter of the device here described is 25 μm and no floating guard rings are present. It is operated in gated mode, with passive quenching, for the characterization. The dark count rate is in the order of few kilo-counts per second at 225 K and 5 V of excess bias. The photon timing resolution, measured as the full-width at half maximum of the response to a 20 ps pulsed laser, is about 90 ps, with a clean exponential tail whose time constant is about 60 ps. The photon detection efficiency is about 30% at 1550 nm. These specifications make our InGaAs/InP SPAD a good candidate for advanced time-correlated singlephoton counting applications at wavelengths up to 1700 nm.