Coupling Single Photons from Discrete Quantum Emitters in WSe₂ to Lithographically Defined Plasmonic Slot Waveguides

Abstract

We report the observation of the generation and routing of single plasmons generated by localized excitons in a WSe monolayer flake exfoliated onto lithographically defined Au-plasmonic waveguides. Statistical analysis of the position of different quantum emitters shows that they are (3.3 ± 0.7) times more likely to form close to the edges of the plasmonic waveguides. By characterizing individual emitters, we confirm their single-photon character via the observation of antibunching in the signal ( g(0) = 0.42) and demonstrate that specific emitters couple to modes of the proximal plasmonic waveguide. Time-resolved measurements performed on emitters close to and far away from the plasmonic nanostructures indicate that Purcell factors up to 15 ± 3 occur, depending on the precise location of the quantum emitter relative to the tightly confined plasmonic mode. Measurement of the point spread function of five quantum emitters relative to the waveguide with <50 nm precision is compared with numerical simulations to demonstrate the potential for greater increases in the coupling efficiency for ideally positioned emitters. The integration of such strain-induced quantum emitters with deterministic plasmonic routing is a step toward deep-subwavelength on-chip single quantum light sources.

Advances in quantum light emission from 2D materials

“…The routing of single photons was successfully demonstrated in plasmonic [102,103] as well as dielectric waveguide [104][105][106]. Statistical analysis of the position of different quantum emitters coupled to plasmonic waveguides showed that they are more likely to form close to the edges of the waveguides [103] with Purcell factor up to 15 ± 3, thus negating the need for pick and place. The coupling of single localized defects in a WSe 2 monolayer was shown to self-align to the surface plasmon mode of a silver nanowire, thus presenting an average coupling efficiency of 26 ± 11%.…”

Site-selectively generated photon emitters in monolayer MoS2 via local helium ion irradiation

“…Beyond the response of mobile excitons, also quantum dot-like emission from localized excitons was recently demonstrated in WSe 2 10–14 , GaSe 15 , MoSe 2 16 , and WS 2 17 and the nature of the potential, which localizes the excitons is still not fully understood. The origin of such quantum emitters was hitherto considered to be caused by uncontrolled strain potentials that locally reduce the band gap, thus, funneling the recombination of excitons via a discrete recombination center 17–20 . However, strain potentials are challenging to control, which limits the applicability of such quantum emitters for a prospective integration into quantum photonic circuits 20–25 .…”

Enabling remote quantum emission in 2D semiconductors via porous metallic networks

“…14 This opens opportunities for coupling and/or energy routing between SPE sites in 2D semiconductors for potential applications such as on-chip quantum light sources. [15][16][17] In addition, metal nanostructures can lead to enhanced Purcell factors resulting in increased single-photon emission rates. 9,18 As such, it is natural to imagine interfacing 2D semiconductor SPEs with metals to advance quantum and optical processing technology.…”