Optical and mechanical aspects of packaging single photon avalanche diodes for different applications will be discussed. Particular emphasis will be given to fiber coupling at high photon detection efficiencies over a wide wavelength range.
The construction of a new prototype visible-light intensity interferometer for use in stellar astronomy is described. The instrument is located in New Haven, Connecticut, at Southern Connecticut State University, but key components of the system are also portable and have been taken to existing research-class telescopes to maximize sensitivity and baseline. The interferometer is currently a two-station instrument, but it is easily expandable to several stations for simultaneous measurement using multiple baselines. The design features single photon avalanche diode (SPAD) arrays, which increase the throughput and signal-to-noise ratio of the instrument. Predicted system performance and preliminary observations will be discussed.
With the recent progresses in quantum technologies, single photon sources have gained a primary relevance. Here we present a heralded single photon source characterized by an extremely low level of noise photons, realized by exploiting low-jitter electronics and detectors and fast custom-made electronics used to control an optical shutter (a LiNbO3 waveguide optical switch) at the output of the source. This single photon source showed a second-order autocorrelation function g(2)(0) = 0:005(7), and an Output Noise Factor (defined as the ratio of noise photons to total photons at the source output) of 0:25(1)%, among the best ever achieved.
We present a photon-counting module based on InGaAs/InP SPAD (Single-Photon Avalanche Diode) for detecting
single photons up to 1.7 μm. The module exploits a novel architecture for generating and calibrating the gate width,
along with other functions (such as module supervision, counting and processing of detected photons, etc.). The gate
width, i.e. the time interval when the SPAD is ON, is user-programmable in the range from 500 ps to 1.5 μs, by means of
two different delay generation methods implemented with an FPGA (Field-Programmable Gate Array). In order to
compensate chip-to-chip delay variation, an auto-calibration circuit picks out a combination of delays in order to match
at best the selected gate width. The InGaAs/InP module accepts asynchronous and aperiodic signals and introduces very
low timing jitter. Moreover the photon counting module provides other new features like a microprocessor for system
supervision, a touch-screen for local user interface, and an Ethernet link for smart remote control. Thanks to the fullyprogrammable
and configurable architecture, the overall instrument provides high system flexibility and can easily
match all requirements set by many different applications requiring single photon-level sensitivity in the near infrared
with very low photon timing jitter.
We present the design and performances of a radiation detector based on plastic scintillating fibers with doubleside readout by means of large-area Single Photon Avalanche Diodes (SPAD). This can be the basic step toward the realization of a large-area, cost-effective position sensitive detector to be employed in future space gammaray observatories. SPADs are silicon devices operated above the junction breakdown voltage (with the typical overvoltage of 5V), for which a single photon interacting in the active region is sufficient to trigger a selfsustainable avalanche discharge. SPADs can thus be used for the detection of very low light levels with a fast time response around 50ps FWHM for single photon detection, without spectroscopic capabilities. Large-area SPAD (500 μm in diameter) have been designed and fabricated at the CNR-IMM facility, with an intrinsic noise lower than 10kHz at -15°C, and are optically coupled to both ends of 3-meter long scintillating fibers, with the same diameter. Double-side readout is required to operate the devices in coincidence (10ns coincidence window), in order to reduce the rate of false detections to the level of 1Hz. The detectors have been tested with minimum ionizing particles at CERN PS demonstrating a detection efficiency larger than 90% and a moderate position resolution along the fiber due to the difference in time of arrival between the two photodetectors. Radiation hardness tests on SPADs have also been carried out, showing that large-area SPADs can be safely employed in low-inclination low Earth orbits.
In the last years many progresses have been made in the field of silicon Single Photon Avalanche Diodes (SPAD) thanks to the improvements both in device design and in fabrication technology. Particularly, the Dipartimento di Elettronica e Informazione of Politecnico di Milano and the CNR-IMM of Bologna have been in the forefront of this research activity by designing and fabricating a new device structure enabling the fabrication of SPADs with red enhanced photon detection efficiency. In this paper we present a compact photon counting and timing module that fills the gap between the high temporal resolution and the high detection efficiency systems. The module exploits Red-Enhanced SPAD technology to attain a Photon Detection Efficiency (PDE) as high as 37% at 800 nm (peak of 58% at 600 nm) while maintaining a temporal resolution of about 100 ps FWHM, even with light diffused across the whole active area. A thermo-electric cooling system guarantees a noise as low as few counts per second for a 50 μm diameter SPAD while a low threshold avalanche pick-up circuit assures a limited shift in the temporal response.
Three dimensions (3D) acquisition systems are driving applications in many research field. Nowadays 3D acquiring
systems are used in a lot of applications, such as cinema industry or in automotive (for active security systems).
Depending on the application, systems present different features, for example color sensitivity, bi-dimensional image
resolution, distance measurement accuracy and acquisition frame rate. The system we developed acquires 3D movie
using indirect Time of Flight (iTOF), starting from phase delay measurement of a sinusoidally modulated light. The
system acquires live movie with a frame rate up to 50frame/s in a range distance between 10 cm up to 7.5 m.
Until very recently Single Photon Avalanche Diodes (SPAD), which yield high detection efficiency in the visible spectrum, provided poor timing performance. This paper will review the current state of the SPAD technology and review new SPAD developments that provide: sub 50ps-timing resolution, are stable with count rate, and yield high detection efficiency. Examples will be provided; comparing timing resolution of PMT's and solid-state photon counting modules, effect of count rate on timing resolution, thus illustrating the stability of these newly developed SPAD's. In addition, the paper will review the basics of photon counting using SPAD's and illustrate how these SPAD's are used in Time-Correlated Single Photon Counting (TCSPC) and the results from these experiments.
In this paper we report the results relative to the design and fabrication of Single Photon Avalanche Detectors (SPAD) operating at low voltage in planar technology. These silicon sensors consist of pn junctions that are able to remain quiescent above the breakdown voltage until a photon is absorbed in the depletion volume. This event is detected through an avalanche current pulse.
Device design and critical issues in the technology are discussed.
Experimental test procedures are then described for dark-counting rate, afterpulsing probability, photon timing resolution, quantum detection efficiency. Through these experimental setups we have measured the electrical and optical performances of different SPAD technology generations. The results from these measurements indicate that in order to obtain low-noise detectors it is necessary to introduce a local gettering process and to realize the diode cathode through in situ doped polysilicon deposition. With such technology low noise detectors with dark counting rates at room temperature down to 10c/s for devices with 10mm diameter, down to 1kc/s for 50mm diameter have been obtained.
Noticeable results have been obtained also as far as time jitter and quantum detection efficiency are concerned.
This technology is suitable for monolithic integration of SPAD detectors and associated circuits. Small arrays have already been designed and fabricated. Preliminary results indicate that good dark count rate uniformity over the different array pixels has already been obtained.