Studying photon number distribution of NV-centre-emission in diamond

The present work focuses on laser excited nitrogen vacancies (NV-centres) in nanodiamonds. The emitted fluorescence of the investigated centres is observed after spectral filtering at (697 + 37) nm. To obtain the photon number distribution of different NV centres, the diagonal elements of the density matrix were experimentally determined using a transition-edge sensor (TES). This photon number resolving detector produces an output pulse proportional to the number of photons absorbed. Due to the absence of the two photon component, the g⁽²⁾(t = 0)-value calculated from the data is <; 0.01. The corresponding g⁽²⁾ function was measured by a Hanbury-Brown-Twiss (HBT) interferometer consisting of two single photon avalanche photodiodes (SPADs) and a beam splitter. By fitting the HBT-data, a g⁽²⁾(t = 0)-value of 0.03 ± 0.03 is determined, thus comparable with the TES value.