Plasmonic Enhancement of Single Photon Emission from a Site-Controlled Quantum Dot

Abstract

We showed enhanced single photon emission via exciton-plasmon coupling in a metal-encapsulated site-controlled quantum dot (QD) structure. It was observed that the average QD luminescence was enhanced by a factor of 7.33 ± 1.32 and the exciton lifetime was reduced by a factor of 12.8 ± 1.10. The exciton-plasmon coupling was enhanced by matching the exciton energy to the localized surface plasmon resonance. Due to the sensitivity of the plasmonic enhancement to dot-to-dot variations, measurements were performed on the same dot at different stages of the sample processing, enabled by the use of a novel site-controlled InGaN QD structure. This was then repeated over a large number of dots and compared between different metal materials to investigate the nature of the coupling.KEYWORDS: plasmonic coupling, metallic cavity, quantum dots, III-nitride, single photon emission, site-control On-demand single-photon emission (SPE) has broad applications in quantum science and technologies. Epitaxial semiconductor quantum dots (QDs) intrinsically offer a higher repetition rate 1,2 than atoms, 3 molecules, 4 colloidal QDs, 5,6 and nitrogen vacancies (NV) in diamonds, 7,8 and therefore are a good candidate for high-speed operations. Group III-nitride (III-N) QDs are of high interest due to their potential for SPE beyond cryogenic temperatures, 9,10 which is beneficial for practical deployment of quantum cryptography and low-power communications. 11 However, the strong piezoelectric field in strained III-N heterostructures can cause long radiative lifetimes on the order of tens of nanoseconds, limiting their operating speed to only tens of MHz. 12 The field also reduces the radiative efficiency due to the separation of electron and hole wavefunctions. Shortening the radiative lifetime can make III-N QDs faster and brighter.Photonic crystals 13-15 and metallic cavities [16][17][18] have been widely explored in III-V QD systems.

Photophysics of GaN single-photon emitters in the visible spectral range

“…Gallium nitride (GaN) is one such material. For instance, GaN quantum dots (QDs) have been incorporated into nanoscale pillars to generate bright single photons sources in the UV spectral range at cryogenic temperatures and, to some extent, at room temperature (RT) [19][20][21]. It has also recently been shown that defects in GaN can act as polarized, bright SPEs that operate at RT emitting in the visible [22,23] and telecom spectral range [24].…”

Patterned Plasmonic Surfaces—Theory, Fabrication, and Applications in Biosensing

“…Compared to the topographic resolution of 50 nm, the relatively coarse optical resolution of 400 nm can be further improved through QD-plasmonic coupling and plasmonic enhancement [114]. With the capability from near UV to IR emission, plasmonic enhanced, mass-producible, and self-illuminating nano-LED on-chip will open up many exciting opportunities in biomedical and industrial applications, including near-field microscopy of subcellular structures, direct material patterning, and compact “light-on-chip” biosensors and biochips.…”

“…With the capability from near UV to IR emission, plasmonic enhanced, mass-producible, and self-illuminating nano-LED on-chip will open up many exciting opportunities in biomedical and industrial applications, including near-field microscopy of subcellular structures, direct material patterning, and compact “light-on-chip” biosensors and biochips. Plasmonic structures including plasmonic microplates [115], thin metal films [116], gold colloids [117], plasmonic wells [114], and plasmonic nanogratings [19] have been applied to enhance luminescence of QDs.…”

Enhancing the photon-extraction efficiency of site-controlled quantum dots by deterministically fabricated microlenses

“…[10] In order to upscale the realization of QD-based SPSs and to eventually enable such appealing applications, one needs to apply advanced growth techniques which allow for the site-controlled nucleation of single QDs. Prominent examples for the realization of site-controlled QDs are based on top-down etching techniques, [11] site-selective growth on nanohole-arrays, [12,13,14] inverted pyramids [15,16] and buried-stressors [17] respectively. In this Letter we present a concept which combines the advantages of site-controlled growth, in-situ electron-beam lithography and microlenses to realize highly efficient single-photon emitters in a potentially scalable nanotechnology platform.…”