Monolayer-Based Single-Photon Source in a Liquid-Helium-Free Open Cavity Featuring 65% Brightness and Quantum Coherence

Abstract

Solid-state single-photon sources are central building blocks in quantum information processing. Atomically thin crystals have emerged as sources of nonclassical light; however, they perform below the state-of-the-art devices based on volume crystals. Here, we implement a bright single-photon source based on an atomically thin sheet of WSe 2 coupled to a tunable optical cavity in a liquid-helium-free cryostat without the further need for active stabilization. Its performance is characterized by high single-photon purity (g (2) (0) = 4.7 ± 0.7%) and record-high, first-lens brightness of linearly polarized photons of 65 ± 4%, representing a decisive step toward real-world quantum applications. The high performance of our devices allows us to observe two-photon interference in a Hong–Ou–Mandel experiment with 2% visibility limited by the emitter coherence time and setup resolution. Our results thus demonstrate that the combination of the unique properties of two-dimensional materials and versatile open cavities emerges as an inspiring avenue for novel quantum optoelectronic devices.

Revealing Dark Exciton Signatures in Polariton Spectra of 2D Materials

“…Based on a microscopic many-particle theory, we predict that under certain conditions, polaritons can efficiently scatter into dark exciton states, giving rise to sharp step-like changes both in polariton absorption and reflection as well as in the polariton linewidth. The prediction is confirmed in our measurements on TMD monolayers integrated into fully spectrally tunable open microcavities …”

One (photon), two(-dimensional crystals), a lot (of potential): a quick snapshot of a rapidly evolving field

“…An increased quantum efficiency was also achieved for GaP nanoantennas [203], while silicon nitride dimer nanoantennas, with square cross-section, not only led to a reduction of the SPEs' lifetimes, but also provided control over the emitter polarisation by varying the dimer orientation [204]. Optical cavities employing distributed Bragg reflectors also led to emission enhancements [205], which become even more drastic when an adjustable top mirror allows for the precise tuning of the Fabry-Perot cavity [206].…”

Tailoring Polarization in WSe2 Quantum Emitters through Deterministic Strain Engineering

“…The strong degree of linear polarization is attributed to the nanowrinkles, which give rise to a localized one-dimensional strain potential, thus forming strongly aligned dipoles. 26,33 In addition, the fitting reveals that the in-plane polarization profile of each emitter does follow the directionality of their respective nanowrinkles. Hence, the proposed design facilitates the successful fabrication of spatially isolated SPEs in monolayer WSe 2 .…”

“…Similar to QDs, efficient single-photon emission can be obtained from an SPE in a TMD by placing it inside an optical cavity and exploiting cQED. A WSe 2 emitter was recently placed inside an open cavity geometry 26 leading to the demonstration of an efficiency of ∼ 0.65 and an indistinguishability of ∼ 0.02. The cQED effect relies on a matching of polarizations of the dipole of the emitter and the electric field of the optical cavity mode.…”

“…The polarization of the SPE dipole is then aligned 18,25,27 with the orientation of the wrinkle. Control of the lateral dipole orientation is unnecessary in a rotationally symmetric geometry 26 with two degenerate orthogonally polarized optical cavity modes, where the dipole can couple into either mode. However, the general case requires control of the SPE dipole polarization, and thus the wrinkle orientation, to efficiently couple light into, for example, the polarized TE mode of a planar ridge waveguide as needed for on-chip integrated quantum photonics.…”