Instabilities in nanodiamond nitrogen-vacancy centre single photon sources under prolonged pulsed excitation

Abstract

Colour centres in nanodiamonds provide robust sources of fluorescence and can be used as triggered sources of single photons at room temperature. However, practical devices require stability over thousands of hours of operation, and the use of strong pulsed optical excitation, placing significant burden on the robustness of the emitters that requires bespoke testing. In this work we report the response of single NV centres in nanodiamonds of 50 nm and 100 nm diameter to accelerated lifetime testing, exciting the defects close to saturation around 1013 times to simulate the minimum operational lifetime of a practical device. For nanodiamonds 50 nm in diameter, observed changes in the fluorescence intensity and lifetime suggest a progressive size reduction as a result of the pulsed laser excitation, combined with the introduction of non-radiative centres on or near the nanodiamond surface which affect the quantum efficiency of the NV centre and ultimately lead to photobleaching of the emission. We find examples of NV centres in 100 nm nanodiamonds for which triggered single photon emission remains stable for over these accelerated lifetime tests, demonstrating their suitability for use in practical devices.

Creation, Control, and Modeling of NV Centers in Nanodiamonds

“…The different resonant coupling strengths for randomly located quenchers around the luminescent center result in a deformed exponential decay rate [40,43,44] (Equation 18): accuracy, c is set to ½ and the value of 𝜏 is imposed equal to 80 ns. Although atypical, similarly high values of lifetime have been already reported in literature, [45] motivated by Purcell effect which determines higher lifetime in NDs with respect to bulk diamond. [4G] The difference with respect to typical NV − 𝜏 values (18-25 ns [30,47] ) is justified by the different decay rate model employed in this work, which separately accounts for the contribution of the quenching effect described by k parameter.…”

Engineering a mechanically stable hybrid photonic crystal cavity coupled to color defects in diamond

“…In comparison to hybrid photonic crystal cavity structures with NV − centers in nanodiamonds, e.g. in [17], our hybrid photonic crystal cavity with NV − center in diamond nanopillar (from bulk single-crystal diamond) has the advantage of better coherence properties [37] and photo-stability of emission [38]. Referring to figures 1(a) and (b), in our waveguide based cavity design, the nanobeam is supported by SiO 2 layer to provide the mechanical robustness in contrary to the free-standing nanobeam.…”