Absolute quantum efficiency measurement of single photon emitters in hexagonal Boron Nitride

Single photon emitters in two-dimensional hexagonal boron nitride (hBN) have been intensively studied for several years, since their outstanding properties could qualify this material system as promising candidates for future sources of quantum states of light [1]. However, the atomic origin and some important basic properties of these defects are yet unknown. One of them is the quantum efficiency (QE) with respect to the ratio of radiative and non-radiative rate. We have performed an absolute measurement using the Drexhage method, which is free of incomplete excitation saturation, indirect excitation paths and the detection efficiency of the setup. Instead, it relies on lifetime measurements alongside a controlled change in local density of states achieved by a precise mirror placement using an atomic force microscope. In this contribution, we will report on the mentioned method, the experimental results on two emitter families with different QEs (with the highest QE found approaching 87(7) %) [2], the discovery of part of the underlying level system, specifically the absolute de-excitation rates, and the effects on the expected maximum photon count rate.
[1] Tran, et al., Nature Nanotechnology 11.1 (2016): 37.
[2] Nikolay, et al., Optica 6, 1084-1088 (2019).