Self-aligned deterministic coupling of single quantum emitter to nanofocused plasmonic modes

Abstract

The quantum plasmonics field has emerged and been growing increasingly, including study of single emitter-light coupling using plasmonic system and scalable quantum plasmonic circuit. This offers opportunity for the quantum control of light with compact device footprint. However, coupling of a single emitter to highly localized plasmonic mode with nanoscale precision remains an important challenge. Today, the spatial overlap between metallic structure and single emitter mostly relies either on chance or on advanced nanopositioning control. Here, we demonstrate deterministic coupling between three-dimensionally nanofocused plasmonic modes and single quantum dots (QDs) without any positioning for single QDs. By depositing a thin silver layer on a site-controlled pyramid QD wafer, three-dimensional plasmonic nanofocusing on each QD at the pyramid apex is geometrically achieved through the silver-coated pyramid facets. Enhancement of the QD spontaneous emission rate as high as 22 ± 16 is measured for all processed QDs emitting over ∼150-meV spectral range. This approach could apply to high fabrication yield onchip devices for wide application fields, e.g., high-efficiency light-emitting devices and quantum information processing.exciton-photon coupling | plasmonic nanofocusing | deterministic coupling | single-quantum emitter | Purcell effect S olid-state quantum photon sources based on semiconductor quantum dots (QDs) are a promising platform to realize scalable quantum technology (1-7). However, owing to the extremely small size of QDs (a few tens of nanometers) compared with the wavelength of light (a few hundreds of nanometers), the QD interaction with the photon field is very poor. This poor interaction results in rather low intrinsic spontaneous emission (SE) rates (8, 9), limiting the optical properties of single QDs: low repetition rate, higher sensitivity to thermally activated nonradiative processes and to dephasing from solid-state environment, etc. To overcome these limitations, there have been extensive efforts during the past decade to achieve deterministic coupling of a QD to intense photonic modes for strong Purcell effect (10-13), which demands spectral and spatial overlap between them. Due to the uncertainty of the size and position of the QD, it is still quite challenging and requires sophisticated control techniques, such as scanning probe microscopy and nanoscale positioning system (12,14,15). Therefore, demonstration of deterministic coupling is limited to few devices because the process has to be customized for each QD on the wafer.Nanofocusing of surface plasmon polaritons, beyond the light diffraction limit, has recently seen rapid development. This nanofocusing can be achieved using various tapered metallic structures, such as a sharp metal edge, V-shaped wedges, and tapered waveguides (16-21). Tapering a metallic structure in all three dimensions, instead of only two, is considered ideal for ultimate light focusing (20, 21). The resulting extremely small mode volume can permit strong coupl...

Ultraslow waves on the nanoscale

“…This last feature -that the bandwidth can be enhanced and engineered "by design" at the nanoscale -is a key characteristic of the herein reviewed (ultra)slow-light structures. Specific applications range from enhanced and more efficient nonlinear effects (68,73,74,108), to light-harvesting (64,83,89), bio-sensing (87,88), nano-imaging (80,111), optical and acoustic spectral demultiplexing (40-42, 55, 56, 61, 62, 64, 68, 75-81), on-chip spectroscopy (82), non-classical light sources (90,91), cavity-free plasmonic nanolasing (92)(93)(94), enhanced acoustic sensors operating beyond the noise-threshold limit (61,62), and tunable, deepsubwavelength, ultraslow guided Dirac fermions (102,103), plasmons and surface phononpolaritons in atomically-thin crystals and heterostructures (104)(105)(106)(107)(108)(109)(110). Broadband slow-light effects are also attained in other structures above the diffraction-limit, including photonic crystals and CROWs where broadband slow light is usually obtained with group indices of ~30-100 (21)(22)(23)(24)(25)(26)(27)(28), and PT-symmetric structures, which can be broadband and with the light speed reducing to zero at the exceptional point (58,114).…”

Controlling the spectroscopic properties of quantum dots via energy transfer and charge transfer interactions: Concepts and applications

“…[139] Enhancements are observed at larger separation distance where energy transfer quenching is weaker, and they are often much easier probed using single molecule spectroscopy. [140] Such effects are also easier to observe when the starting fluorophores exhibit rather weak quantum yield. It has been less commonly observed for structures involving AuNPs in solution phase.…”

Dipolar and quadrupolar excitons coupled to a nanoparticle-on-mirror cavity

“…In the quest for ultra-compact nonclassical light sources, new design strategies for plasmonic devices are required [7]. In order to develop functionalities operating with single photons [8][9][10], the interaction between quantum emitters (QEs) and the electromagnetic (EM) fields associated with SPs must be enhanced, and even pushed beyond the weak coupling regime [11]. This demands nanostructures yielding extremely large and highly structured spectral densities, in a similar way as nanoantennas do.…”