We report the incorporation of an ensemble of G centers in silicon-on-insulator (SOI) microrings using ion implantation and conventional nanofabrication. The coupling between the emitters and the resonant modes of the microrings is studied using continuous-wave and time-resolved microphotoluminescence (PL) experiments. We observe the resonant modes of the microrings on PL spectra, on the wide spectral range that is covered by G center emission. By finely tuning the size of the microrings, we match their zero-phonon line at 1278 nm with a resonant mode of quality factor around 3000 and volume 7.2 (λ/n)3. The zero-phonon line intensity is enhanced by a factor of 5, both in continuous-wave and time-resolved measurements. This is attributed to the Purcell enhancement of zero-phonon spontaneous emission into the resonant mode and quantitatively understood considering the distribution of the G center dipoles. Despite the enhancement of the zero-phonon emission, we do not observe any sizeable decrease in the average lifetime of the G centers, which points at a low radiative yield (<10%). We reveal the detrimental impact of parasitic defects in heavily implanted silicon and discuss the perspectives for quantum electrodynamics experiments with individual color centers in lightly implanted SOI rings. Our results provide key information for the development of deterministic single-photon sources for integrated quantum photonics.
We report the incorporation of an ensemble of G centers in silicon-on-insulator (SOI) microrings using ion implantation and conventional nanofabrication. The coupling between the emitters and the resonant modes of the microrings is studied using continuous-wave and time-resolved microphotoluminescence (PL) experiments. We observe the resonant modes of the microrings on PL spectra, on the wide spectral range that is covered by G center emission. By finely tuning the size of the microrings, we match their zero-phonon line at 1278 nm with a resonant mode of quality factor around 3000 and volume 7.2 (λ/n)3. The zero-phonon line intensity is enhanced by a factor of 5, both in continuous-wave and time-resolved measurements. This is attributed to the Purcell enhancement of zero-phonon spontaneous emission into the resonant mode and quantitatively understood considering the distribution of the G center dipoles. Despite the enhancement of the zero-phonon emission, we do not observe any sizeable decrease in the average lifetime of the G centers, which points at a low radiative yield (<10%). We reveal the detrimental impact of parasitic defects in heavily implanted silicon and discuss the perspectives for quantum electrodynamics experiments with individual color centers in lightly implanted SOI rings. Our results provide key information for the development of deterministic single-photon sources for integrated quantum photonics.
Generating single photons on demand in silicon is a challenge to the scalability of silicon-on-insulator integrated quantum photonic chips. While several defects acting as artificial atoms have recently demonstrated an ability to generate antibunched single photons, practical applications require tailoring of their emission through quantum cavity effects. In this work, we perform cavity quantum electrodynamics experiments with ensembles of artificial atoms embedded in silicon-on-insulator microresonators. The emitters under study, known as W color centers, are silicon tri-interstitial defects created upon self-ion implantation and thermal annealing. The resonators consist of circular Bragg grating cavities, designed for moderate Purcell enhancement ( F p = 12.5) and efficient luminescence extraction (η coll = 40% for a numerical aperture of 0.26) for W centers located at the mode antinode. When the resonant frequency mode of the cavity is tuned with the zero-phonon transition of the emitters at 1218 nm, we observe a 20-fold enhancement of the zero-phonon line intensity, together with a 2-fold decrease of the total relaxation time in time-resolved photoluminescence experiments. Based on finite-difference time-domain simulations, we propose a detailed theoretical analysis of Purcell enhancement for an ensemble of W centers, considering the overlap between the emitters and the resonant cavity mode. We obtain a good agreement with our experimental results assuming a quantum efficiency of 65 ± 10% for the emitters in bulk silicon. Therefore, W centers open promising perspectives for the development of on-demand sources of single photons by harnessing cavity quantum electrodynamics in silicon photonic chips.
Monolithic integration of single-photon sources into silicon photonics offers a compelling solution for realizing scalable quantum telecommunication architectures. Among the candidate silicon color centers, the C-center features a zero-phonon emission in the telecom L-band, corresponding to the spectral window of minimum transmission loss in optical fibers. Despite this advantage, isolating single C-centers has remained an unrealized challenge in solid-state quantum optics. In this work, we report the isolation of a single silicon C-center. We enhance the spontaneous emission rate of the zero-phonon line by coupling the single emitter to a nanophotonic crystal cavity, observing a fivefold reduction in the excited-state lifetime compared to bulk conditions, which corresponds to a Purcell factor lower bound of 33. Second-order autocorrelation measurements confirm single-photon emission from the investigated defect, obtaining an optical purity of g(2)(0)=0.23 without background correction. Our results establish a native telecom L-band quantum light source in silicon, laying the foundation for ultra-low-loss and long-distance quantum applications.
Photons are excellent carriers of quantum information. The generation, manipulation and read-out of photonic quantum states have enabled pioneering investigations in quantum physics, paving the way to groundbreaking technologies. Integrated quantum photonics, that is the processing of photons on-chip, is at the forefront of this revolution. In particular, silicon integrated circuits have emerged as the dominant material platform for large-scale quantum photonics. However, the difficulty to inject single photons on-demand in a silicon chip is a major obstacle to the level of complexity of current systems. In this context, the isolation of individual fluorescent defects in silicon, called color centers, opens an avenue toward the integration of atomic sources of single photons. While several color centers have demonstrated an ability to generate antibunched photons, practical applications require tailoring of their emission through quantum electrodynamics effects in optical cavities.This PhD thesis is devoted to cavity quantum electrodynamics with color centers in silicon optical cavities, in view of building an efficient source of single photons. The efforts are first focused on ensembles of G centers in microring cavities. The optical properties of cavity-coupled G centers are studied using microphotoluminescence spectroscopy, and an enhancement of their zero-phonon emission rate by Purcell effect is demonstrated. However, a quantitative analysis reveals a poor quantum efficiency, motivating the choice of another emitter for further experiments. Subsequently, the efforts are focused on the W center. Purcell enhancement of the overall recombination rate is observed for an ensemble of W centers in a circular Bragg grating cavity. Using a quantitative analysis based on finite-difference time-domain calculation, a high quantum efficiency is estimated. The results being encouraging for the purpose of single photon emission, an optical setup is developed for single-emitter spectroscopy and a strategy is devised to fabricate individually-adressable emitters, leading to the isolation of single W centers in unpatterned silicon-on-insulator. Using a nanofabrication process allowing for deterministic positionning, the emitters are embedded into circular Bragg grating cavities, resulting in an increase of the photoluminescence intensity by orders of magnitude by Purcell effect. This work leads to the demonstration of a source of triggered single photons.A next milestone will be the demonstration of a single photon source for integrated photonic circuits, based on a color center in a waveguide-coupled optical cavity. Beyond the interest for integrated quantum photonics, the observation of bright photoluminescence from single color centers opens perspectives for further experiments, allowing to probe fundamental questions relative to their photophysics.
Resonantly enhanced emission from the zero-phonon line of a diamond nitrogen-vacancy (NV) center in single crystal diamond is demonstrated experimentally using a hybrid whispering gallery mode nanocavity.A 900 nm diameter ring nanocavity formed from gallium phosphide, whose sidewalls extend into a diamond substrate, is tuned onto resonance at a low temperature with the zero-phonon line of a negatively charged NV center implanted near the diamond surface.When the nanocavity is on resonance, the zero-phonon line intensity is enhanced by approximately an order of magnitude, and the spontaneous emission lifetime of the NV is reduced by as much as 18%, corresponding to a 6.3X enhancement of emission in the zero photon line.
Silicon G centers show significant promise as single photon sources in a scalable silicon platform. But these color centers have large nonradiative decay and a low Debye-Waller factor, limiting their usability in quantum applications. In this work, we demonstrate bright Purcell-enhanced emission from a silicon G center by coupling it to a nanophotonic cavity. The nanobeam cavity enhances the spontaneous emission rate of a single G center by a factor of 6, corresponding to a Purcell factor greater than 31 when accounting for decay into the phonon sideband. We obtain a spontaneous emission rate of 0.97 ns, which is the fastest single photon emission rate reported in silicon. With this radiative enhancement, we achieve an order of magnitude improvement in emitter brightness compared to previously reported values. These results pave the way for scalable quantum light sources on a silicon photonic chip.
Artificially tailoring quantum emitters by coupling them to optical cavities is critical for applications such as all-photonic quantum computing and quantum key distribution. Among quantum emitters, diamond defect centers, with their atomic-like characteristics, have drawn intense interest for quantum applications. However, the spontaneous emission lifetime of single photons from diamond defects has been limited to several hundred picoseconds, partly due to challenges in realizing cavities in diamond with sufficiently small mode volumes. Here, we sandwich an only 10 nm diamond membrane with implanted negatively charged silicon vacancy centers (SiV – ) between a gold mirror and arrays of nanodisks, resulting in ultrafast single-photon sources with lifetimes as short as 5.5 ps. This corresponds to an improvement in the radiative spontaneous emission rate of over 700-fold, also termed the Purcell factor, and is the result of a greatly enhanced local density of states in the ultrasmall mode-volume cavities. Furthermore, the cavity-coupled single SiV – centers exhibit a 4800-fold photoluminescence enhancement with a single-photon generation rate of up to 361 Mcps at room temperature. These results could refine the engineering of diamond defect centers and position other solid-state platforms as strong quantum-information contenders when coupled to ultrasmall mode-volume cavities, thus illustrating the potential for large-scale, artificially tailored single-photon sources.