Fig. 3: Strain tuning of single waveguide-coupled G-centers.

a Photoluminescence (PL) emitted from waveguide-coupled G-centers collected from the edge coupler and detected with SNSPDs, as a function of the excitation laser position (λ_exc = 532 nm). The PL is filtered with a broadband free-space bandpass filter (1250–1300 nm). Two G-center spots within the waveguide are identified as A and B and are sketched in the inset. b Several zero-phonon lines are observed on the spectrometer at locations A (blue) and B (orange). The central wavelengths shift with the applied DC voltage. The white lines indicate the Lorentzian fit. c Integrated intensity on the spectrometer as a function of excitation power on emitter B. The yellow line indicates the fit to power saturation of a two-level system, from which we extract a saturation power of P_sat = (13.6 ± 0.5) μW. d Second-order correlation function of the filtered zero-phonon line shown in (c), excited in continuous-wave at saturation, with a measured g⁽²⁾(0) = 0.09 ± 0.04. The yellow line represents a fit to a three-level system, including a dark state, which gives rise to antibunching and bunching timescales. The dashed orange line indicates the threshold below which emission from a single emitter is demonstrated. e Time-resolved measurement of the zero-phonon line A₂ under pulsed above-band excitation, close to saturation. The lifetime extracted from a mono-exponential decay, τ = (6.61 ± 0.09) ns, is typical of G-centers.