Optimizing the use of detector arrays for measuring intensity correlations of photon pairs

Abstract

Intensity correlation measurements form the basis of many experiments based on spontaneous parametric down-conversion. In the most common situation, two single-photon avalanche diodes and coincidence electronics are used in the detection of the photon pairs, and the coincidence count distributions are measured by making use of some scanning procedure. Here we analyze the measurement of intensity correlations using multielement detector arrays. By considering the detector parameters such as the detection and noise probabilities, we found that the mean number of detected photons that maximizes the visibility of the two-photon correlations is approximately equal to the mean number of noise events in the detector array. We provide expressions predicting the strength of the measured intensity correlations as a function of the detector parameters and on the mean number of detected photons. We experimentally test our predictions by measuring far-field intensity correlations of spontaneous parametric down-conversion with an electron multiplying charge-coupled device camera, finding excellent agreement with the theoretical analysis.

General Model of Photon-Pair Detection with an Image Sensor

“…Recent works have revealed some features of entanglement between pairs of photons generated by SPDC [20,21], but these techniques have not retrieved the full characteristics the photon pairs, i.e., their full joint probability distribution. Moreover, the theoretical analyses associated with these works were carried out under approximations on the form of the correlation [26][27][28]. In particular, these works assumed a regime of detection in which the two photons never hit the same pixel of the camera, which is counterintuitive when measuring pairs that are strongly correlated in position.…”

Optimizing the signal-to-noise ratio of biphoton distribution measurements

“…The red curve shows Eq. (22) with ⟨ ⟩ = ⟨ ⟩ opt and the known dependence of on threshold, i.e., ( > |0). There is agreement between theory and experiment for all but the highest thresholds, which correspond to the lowest values .…”

“…The goal of this work is to provide a prescription for optimizing the measurement of the biphoton joint probability distribution. Prior work has examined maximizing the visibility of the genuine biphoton coincidences relative to the accidentals background [22]. There, the authors found an optimum visibility when the count rate from photons is equal to that from electronic noise events but noted that the SNR could be improved by increasing the count rate.…”

Heralded phase-contrast imaging using an orbital angular momentum phase-filter

“…However, our system also allows us to obtain images using very low light levels, as shown in figure 4. The images shown contain between 7300 and 75 000 photons, as counted using the photon counting methodology described in [25]. In this method, a threshold signal is applied to each frame read out from the ICCD camera and any signal over this threshold level is counted as a photon.…”