A charge-integration readout circuit with a linear-mode silicon avalanche photodiode for a photon-number resolving detector

A charge-integration readout circuit for a photon-number resolving detector for visible or near-infrared wavelength is presented. In the scheme, photons are converted into electric carriers by a Si APD operating in the linear mode. To read the small number of photo-carriers generated by the Si APD, a charge-integration readout circuit is used. The entire circuit operates at 77 K. The main noise of the readout circuit is attributed to dielectric polarization noise, which is dominant at the operating temperature. The noise of the readout circuit was reduced to 3.0 electrons averaged by a period of 40 ms.