In situ scattering of single gold nanorod coupling with monolayer transition metal dichalcogenides

Plasmon enhanced luminescence of Tb/Eu co-doped film by Au NRs-PVA nanocomposite film

Plasmonic nanostructures have great potential for improving the radiation properties of emitters. Here, the plasmonic Au nanorods-PVA nanocomposite films are used to uniformly improve the photoluminescence of Tb/Eu co-doped PMMA film within the local micro-region. Under the excitation of 292 nm, the maximum enhancement factor is 37.2-fold for emission at 612 nm and 21.6-fold for emission at 545 nm. Moreover, the finite different time domain simulations are developed to further explain the experimental results. It is indicated that the modulation of luminescence can be attributed to the increase of the local density of optical states through the Purcell effect and the improvement of the energy transfer efficiency between Tb and Eu. Under the excitation of 360 nm, the maximum enhancement factor is about 71.5-fold. In this case, the Au nanorods are mainly used for modulating the emission process at 612 nm, which deduced a greater enhancement factor at 612 nm. This study provides a deep understanding of the interactions between rare earth ions co-doped materials and plasmonic nanostructures, building a bridge to fabricate a useful platform for several applications, such as thin film-based detectors and sensors.

Single-particle spectroscopic investigation on the scattering spectrum of Au@MoS2 core-shell nanosphere heterostructure

Owing to the uniform shape of the nanospheres, the Au@MoS₂ core-shell nanosphere heterostructure enables us to design nano-optoelectronic devices and nanosensors with highly tunable and reproducible optical properties. However, until now, at the single-particle level, there is still uncertainty as to how much the scattering characteristics depend on the particle size and the local environment. In this letter, we performed an in situ single-particle study of the scattering spectrum of the Au@MoS₂ core-shell nanosphere heterostructure before and after coating with the MoS₂ layer. Single-particle characterization confirms that the classic quasi-static approximation (QSA) theory can be used to predict the scattering spectra of Au@MoS₂ core-shell nanoparticles. Moreover, we have found that the A and B-exciton absorption peaks do not rely on the local refractive index change, while the position of the particle plasmon resonances does. Such features can be used as an internal reference for sensing applications against measurement errors, such as defocusing the imaging. Our results show that Au@MoS₂ core-shell nanoparticles have the potential to become one of the promising nanosensors in the field of single-particle sensing.

Plasmonic nanobar-on-mirror antenna with giant local chirality: a new platform for ultrafast chiral single-photon emission

Providing an additional degree of freedom for binary information encoding and nonreciprocal information transmission, chiral single photons have become a new research frontier in quantum optics. Without using complex external conditions (e.g., magnetic field, low temperature), coupling emitters to chiral optical antennas has become a promising strategy to efficiently convert single photons from linear to circular polarization states. For ideal chiral single-photon sources, essential properties such as giant Purcell factor, large degree of circular polarization (DCP), and high collection efficiency are highly demanded. Herein, to meet these combined requirements, we propose an emitter-coupled nanobar-on-mirror antenna platform with significant local chirality acquired from the broken symmetry, as well as the giant Purcell factor owing to its ultrasmall mode volume. An emitter embedded at the corner in the gap exhibits above 3 orders of magnitude enhancement of the chiral spontaneous emission with more than 80% collection efficiency, along with up to 70% DCP. Compatible with a myriad of nanoscale quantum emitters (e.g. transition metal dichalcogenides, color centers, quantum dots, etc.), this platform, not only manifests the potential for realizing ultrafast chiral single-photon generator towards GHz and THz operation speed but also provides versatile testbeds for investigating chiral light-matter interaction at the single-quantum level.

Visualization of Plasmonic Couplings Using Ultrafast Electron Microscopy

Hybrids of graphene and metal plasmonic nanostructures are promising building blocks for applications in optoelectronics, surface-enhanced scattering, biosensing, and quantum information. An understanding of the coupling mechanism in these hybrid systems is of vital importance to its applications. Previous efforts in this field mainly focused on spectroscopic studies of strong coupling within the hybrids with no spatial resolution. Here we report direct imaging of the local plasmonic coupling between single Au nanocapsules and graphene step edges at the nanometer scale by photon-induced near-field electron microscopy in an ultrafast electron microscope for the first time. The proximity of a step in the graphene to the nanocapsule causes asymmetric surface charge density at the ends of the nanocapsules. Computational electromagnetic simulations confirm the experimental observations. The results reported here indicate that this hybrid system could be used to manipulate the localized electromagnetic field on the nanoscale, enabling promising future plasmonic devices.