Fully tuneable, Purcell-enhanced solid-state quantum emitters

Abstract

We report the full energy control over a semiconductor cavity-emitter system, consisting of single Stark-tunable quantum dots embedded in mechanically reconfigurable photonic crystal membranes. A reversible wavelength tuning of the emitter over 7.5 nm as well as an 8.5 nm mode shift are realized on the same device. Harnessing these two electrical tuning mechanisms, a single exciton transition is brought on resonance with the cavity mode at several wavelengths, demonstrating a ten-fold enhancement of its spontaneous emission. These results open the way to bring several cavity-enhanced emitters mutually into resonance and therefore represent a key step towards scalable quantum photonic circuits featuring multiple sources of indistinguishable single photons. Last decade has witnessed pioneering advancements in the development of the elementary building blocks for envisioned quantum photonic circuits, 1 which may enable simulating problems, which are intractable on classical computers. 2,3 Efficient on-demand single-photon sources, obtained by coupling a quantum emitter to an optical cavity, represent one of these key building blocks. Additionally, cavity quantum electrodynamics (c-QED) offers a viable solution to create a coherent and efficient interface between light and matter qubits, as needed to establish entanglement between distant quantum emitters via a photonic channel. 4 Among its numerous solid-state implementations, quantum dots (QDs) embedded in semiconductor nano-resonators have emerged as one of the most promising integrated platforms, 5,6 specifically for the on-demand generation of single and entangled photons. 7 Coupling to photonic crystal cavities (PCCs) is notably attractive due to their engineerable electromagnetic environment which provides record quality factors (Q) in a wavelength-scale volume. 8 Indeed, the basic c-QED phenomena have been recently demonstrated, including Rabi splitting, 9 static 10 and dynamic 11,12 control of spontaneous emission and single-photon non-linearities. 13,14 Nevertheless, integrating and interconnecting multiple c-QED nodes within the same chip poses considerable scalability issues.One of the leading experimental challenges in this context resides in the spectral matching of multiple cavityemitter systems, which requires the deterministic control over the energy of both emitters and cavities. To this end, post-processing tuning strategies are imperative because of the QD inhomogeneous broadening and the intrinsic fabrication imperfections which spread the actual cavity resonance over several nanometers.Lately, a number of techniques based on electric, magnetic, temperature and strain control have been successfully employed to tune the emitters' energy. 5 On the other hand, several proposals have been adopted to tune the cavity spectrum, including thermal methods, 15 gas adsorption, 16 photochromic materials, 17 photo-oxidation, 18 free carrier injection, 19,20 and nano-electromechanical systems. [21][22][23] However, so far, the crucial goal of achieving a simu...

Material platforms for integrated quantum photonics

“…At the same time, the III-V platform faces significant challenges for producing large-scale QPICs. While deterministic on-chip QDs placement has so far produced promising results [69], achieving photon indistinguishability between different QDs still requires complicated tuning [74] or quantum frequency conversion [75] which is an active area of research by itself [76]. Finally, larger linear losses in III-V based waveguides compared to Si-based waveguides limit the achievable circuit complexities.…”

Electrically driven quantum light emission in electromechanically tuneable photonic crystal cavities

“…Instead, when the QD-diode is operated at VQD > 1.2V, the decay time does not depend on the applied voltage. This value corresponds to the radiative time at zero field τbulk = 1.45 ns [38, ( b ) (c) ( a ) 32]. A slower decay component is also visible in the time-resolved data (Figure 4c inset) and is attributed to the presence of a dark exciton repopulating the bright transition.…”

Nano-opto-electro-mechanical switch based on a four-waveguide directional coupler

“…The initial zero-bias gap between suspended waveguides and bottom ones is 220 nm, which is relatively small compared to most MEMS switches in the literature. However, we have demonstrated experimentally several generations of devices based on similar gap scale, which work successfully and reproducibly [26,29,30]. In the symmetric case, the structure is symmetric and works in the cross-state.…”