<title>Photon-counting techniques with silicon avalanche photodiodes</title>

Compact active quenching circuit for fast photon counting with avalanche photodiodes

“…1,38,39 V C typically varies from a few volts for SPADs with thin depletion layer to 6-16 V for SPADs with thick ͑20-35 m͒ depletion regions. 1,38,39 The AQC should, accordingly, be capable of handling excess bias voltages up to 20-30 V in order to achieve a P b value approaching unity.…”

“…The thermal coefficient makes V B rise with the temperature by a remarkable amount, of the order of 0.3%/°C or more. 1,22 At constant supply voltage V A , the increase of V B with temperature causes a decrease of the excess bias voltage V E , which, in percentage, is greater than that of V B by the factor V B /V E , that is, by a factor of 10 and more. The resulting reduction of V E causes a remarkable variation in the detector performance, particularly in the photon detection efficiency ͑see Sec.…”

“…These single photon avalanche diodes ͑SPADs͒ are emerging as a convenient alternative to photomultiplier tubes ͑PMTs͒ in photon counting and timing applications, thanks to their ruggedness, small size, low bias voltage, and high photon detection efficiency in the red and near-infrared ͑NIR͒ range. [1][2][3][4] In recent years, significant experimental results have been obtained with SPADs in various fields: basic quantum mechanics; 5 cryptography; 6 astronomy; 7,8 single molecule detection; 9 luminescence microscopy; 10,11 fluorescent decays and luminescence in physics, chemistry, biology; 12-14 laser diode characterization; 15 optical fiber testing in communications [16][17][18] and in sensor applications; 19 laser ranging in space applications and in telemetry; 20,21 photon correlation techniques in laser velocimetry; and dynamic light scattering. 22,23 Silicon SPADs have been extensively investigated and are nowadays well developed.…”

“…Considerable progress has been achieved in the design and fabrication techniques and devices with good characteristics are commercially available. 1 The devices so far reported can be divided in two groups according to the depletion layer of the pn junction: thin, typically 1 m, 2 or thick, from 20 to 150 m. 1,22,23 Their main features can be summarized as follows. For thinjunction SPADs: ͑i͒ the breakdown voltage V B ranges from 10 to 50 V: ͑ii͒ the active area is small, with diameters from 5 to 150 m; ͑iii͒ the photon detection efficiency is fairly good in the visible range ͑about 45% at 500 nm͒, declines to 32% at 630 nm and to 15% at 730 nm, and is still useful in the NIR, being about 10% at 830 nm and as little as 0.1% at 1064 nm.…”

“…Various AQC types were then developed in our laboratory 30,33,34 and in various other laboratories. 1,7,23,35,36,37 In these circuits, fast transistors, triggered by the avalanche current, are used to quickly lower and then reset the bias voltage. Hence, a short and well-defined time interval ͑currently called deadtime͒ is generated after each avalanche pulse, during which the detector is insensitive to absorbed photons.…”