Speaker
Description
Since 2020, photon antibunching [1-3] and Purcell enhancement [4-5] in cavities have been observed for a variety of point defects acting as color centers in silicon. These results open the way to the development of a first deterministic source of single photons in Si (SPS), with a huge potential impact for the upscaling of integrated quantum photonics on SOI chips.
Building upon previous results on W centers [3,5], we have recently developed the integration of a single W center at the core of SOI bullseye cavities in a deterministic way, with a positioning accuracy on the order of +/- 50 nm and nearly perfect spectral matching between the W center zero-phonon line and the resonant cavity mode (see Christian Elsässer’s poster at EQEP). This presentation is focused on the detailed study of these SPS.
HBT experiments under cw non-resonant pumping unveils a very clean antibunching behavior (g(2)(0)<0.05) over the full range of pump powers, up to saturation of W’s PL. This result highlights the absence of parasitic emitters in the cavity.
We have performed HBT experiments under pulsed excitation, playing with different pump powers and repetition rates. In the weak pumping regime (1-10% of the saturation power), the area A0 of the peak at zero delay is typically 20 smaller than reference peaks at long delays, showing emission of at most one photon as a response to excitation pulses.
This good single photon purity is however lost at large pump powers close to the saturation power, and A0 reaches about 0.5 in normalized units. A careful analysis of the central peak using a fine time binning to build the photon correlation histogram reveals a narrow and well-defined antibunching dip at zero delay at the center of that peak. We attribute these behaviors to a repumping of the W center after emission of a first photon, due to the presence of residual electron-hole pairs inside Si. Quasi-resonant pumping and/or the application of a weak static electric field should mitigate this issue.
We also show that the Purcell effect is at work in our system, as witnessed by a 500-fold increase of the photoluminescence signal at saturation, and by a 3-fold reduction of the emitter’s lifetime. These results demonstrate that the W center ZPL emission experiences a Purcell enhancement in the 6-10 range, to be compared with 13, the highest possible value for a W center that is ideally coupled to the cavity mode. This confirms the accurate positioning of the W center close to the mode antinode, with +/-50 nm precision.
On the basis of these results, we will present the attractive expected performances of a waveguide-coupled SPS made of a single W center in a high-Fp “nanobeam” photonic crystal cavity.
[1] Redjem, W. et al. Nat Electron 3, 738–743 (2020)
[2] Durand, A. et al, PRL 126, 083602 (2021)
[3] Y. Baron et al., ACS Photonics 9 (7), 2337-2345 (2022).
[4] B. Lefaucher et al, APL 122, 061109 (2023)
[5] B. Lefaucher et al., ACS Photonics 11 (1), 24-32 (2024)
