In several applications such as linear optical quantum computing, near-infrared spectroscopy, optical communication and quantum communication, efficient detection of different photon number states is crucial. For these applications, a detector able to measure efficiently the number of photons (in the range 1-10) is highly needed. There are two classes of photon number resolving detectors. One class has intrinsic PNR capability producing an output which is inherently proportional to the number of photons (like in superconducting transition edge sensor). All the other detectors are non linear: this second class must be multiplexes in order to achieve photon number resolving capability. This can be obtained either by combining the output signals of an array of detectors (spatial multiplexing) or by splitting the multiphoton pulse via a cascade of beam splitters and then delaying the signals so that they can be detected sequentially by a single detector (time multiplexing).
In 2012 In collaboration with the group of Photonics and Semiconductor Nanophysics at Eindhoven Technical University, we have demonstrated PNRD with 4 multiplexed elements connected in series. Fig a) shows a a more recent PNRD able to discriminate 0-24 photon levels (Fig. b and c), featuring a 1/e time of 13 ns and a jitter of 116 ps (for 24 photons absorbed). Each nanowire section (folded as a meander) is connected to a parallel resistor (Rp), which is integrated on chip together with the nanowires: voltages produced across each of them due to photon detection events add up at the output making the read-out electronics simpler.
References: Mattioli et al Optical express
24 (8), 9067-9076 (2016)
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