QUANTUM DETECTORS
Single-photon detectors
take quantum leaps

ALEXANDRE PAUCHARD, GREGOIRE RIBORDY, ALEXIS ROCHAS, LEONARD WIDMER,

ROBERT THEW, AND WOLFGANG BECKER

Quantum detectors—including photo- FIGURE 1. A 3 × 3 array of photon counters is integrated on one ^{diodes, photoconductors, phototran-} silicon chip. The squares around the chip are the bonding pads. sistors, charge-coupled detectors

ID QUANTIQUE

(CCDs), and photomul- tubes (PMTs) and micro-tiplier tubes—are devic- ^{Continuing advances in} channel PMTs have been

^{es that convert incoming single-photon detection produced industrially for a} photons directly into an electrical signal, as half century and have long opposed to thermal detectors that rely on the include improvements in since reached maturity. conversion of incoming radiation to heat. Photomultiplier tubes

A growing number of applications require avalanche photodiodes, have large active areas and
the detection of single photons—the ultimate are capable of detecting sin-
limit in detector sensitivity. The availability of frequency upconversion, gle photons. Consisting of a
high-performance photon counters is crucial photoemissive cathode fol-
to continued progress in the fields of quan- ^{and superconducting} lowed by an electron mul-
^{tum information processing, quantum com- photon counters. tiplier and an electron col-} munication, fluorescence analysis, chemical lector (anode), the timing
or biological luminescence analysis, single- resolution of conventional
molecule detection, and light detection and ranging (lidar). PMTs is limited to about 150 ps. A few PMTs have been op-
timized to operate in the near-infrared (NIR) wavelength
Non-solid-state photon counters range from 1000 to 1520 nm, but their quantum efficiency
Among several photon-detection methods, photomultiplier is poor—on the order of 1% (see www.laserfocusworld.com/
articles/245127).

ALEXANDRE PAUCHARD is vice president of engineering, GREGOIRE ^{When highly accurate timing is required, microchannel} RIBORDY is CEO, ALEXIS ROCHAS is manager of detector develop- plates (MCPs) are preferred. Consisting of millions of con- ments, and LEONARD WIDMER is vice president of sales at id Quan- _{ductive capillaries fused together (with diameters in the} tique, Chemin de la Marbrerie, 3, 1227 Carouge, Geneva, Switzerland;

ROBER T THE W is a post-doctorate in the Group of Applied Physics range of 4 to 25 µm), some MCPs can achieve very low tim- at the University of Geneva, 24 rue du Général-Dufour, 1211 Geneva ing jitter of about 25 ps. However, the devices are very ex- 4, Switzerland; WOLFGANG BECKER is president of Becker & Hickl, _{Nahmitzer Damm 30, D-12277 Berlin, Germany ; e-mail: alexandre. pensive and their count rates are limited to a few megahertz.} pauchard@idquantique.com; www.idquantique.com. In addition, MCPs are fragile and bulky, operate under very