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Local deformation of atomically thin van der Waals materials provides a powerful approach to create site-controlled chip-compatible single-photon emitters (SPEs). However, the microscopic mechanisms underlying the formation of such strain-induced SPEs are still not fully clear, which hinders further efforts in their deterministic integration with nanophotonic structures for developing practical on-chip sources of quantum light. Here we investigate SPEs with single-photon purity up to 98% created in monolayer WSe$_2$ via nanoindentation. Using photoluminescence imaging in combination with atomic force microscopy, we locate single-photon emitting sites on a deep sub-wavelength spatial scale and reconstruct the details of the surrounding local strain potential. The obtained results suggest that the origin of the observed single-photon emission is likely related to strain-induced spectral shift of dark excitonic states and their hybridization with localized states of individual defects., Comment: 8 pages, 4 figures

Nanoantennas for highly efficient excitation and manipulation of surface waves at nanoscale are key elements of compact photonic circuits. However, previously implemented designs employ plasmonic nanoantennas with high Ohmic losses, relatively low spectral resolution, and complicated lithographically made architectures. Here we propose an ultracompact and simple dielectric nanoantenna (silicon nanosphere) allowing for both directional launching of surface plasmon polaritons on a thin gold film and their demultiplexing with a high spectral resolution. We show experimentally that mutual interference of magnetic and electric dipole moments supported by the dielectric nanoantenna results in opposite propagation of the excited surface waves whose wavelengths differ by less than 50 nm in the optical range. Broadband reconfigurability of the nanoantennas operational range is achieved simply by varying the diameter of the silicon sphere. Moreover, despite subwavelength size ($, Comment: added relevant references; fixed typos in Supplementary eq. 8,9,11

Optical metasurfaces have great potential to form the platform for manipulation of surface waves. A plethora of advanced surface-wave phenomena utilizing negative refraction, self-collimation and channeling of 2D waves can be realized through on-demand engineering of dispersion properties of a periodic metasurface. In this letter, we report on the first-time direct experimental polarization-resolved measurement of dispersion of 2D optical plasmons supported by an anisotropic metasurface. We demonstrate that a subdiffractive array of strongly coupled resonant anisotropic plasmonic nanoparticles supports unusual optical surface waves with mixed TE- and TM-like polarizations. With the assistance of numerical simulations we identify dipole and quadrupole dispersion bands. The shape of isofrequency contours changes drastically with frequency exhibiting nontrivial transformations of their curvature and topology that is consistently confirmed by the experimental data. By revealing polarization degree of freedom for surface waves, our results open new routes for designing of planar on-chip devices for surface photonics.

Various clusters of metallic or dielectric nanoparticles can exhibit sharp Fano resonances originating from at least two modes interference of different spectral width. However, for practical applications such as biosensing or nonlinear nanophotonics, the fine-tuning of the Fano resonances is generally required. Here, we propose and demonstrate a novel type of hybrid oligomers consisting of asymmetric metal-dielectric (Au/Si) nanoparticles with a sharp Fano resonance in visible range, which has a predominantly magnetic origin. We demonstrate both, numerically and experimentally, that such hybrid nanoparticle oligomers allow fine-tuning of the Fano resonance via fs-laser induced melting of Au nanoparticles at the nanometer scale. We show that the Fano resonance wavelength can be changed by fs-laser reshaping very precisely (within 15~nm) being accompanied by a reconfiguration of its profile.

Hybrid nanophotonics based on metal-dielectric nanostructures unifies the advantages of plasmonics and all-dielectric nanophotonics providing strong localization of light, magnetic optical response and specifically designed scattering properties. Here we demonstrate a novel approach for fabrication of ordered hybrid nanostructures via femtosecond laser melting of asymmetrical metal-dielectric (Au-Si) nanoparticles created by lithographical methods. The approach allows selective reshaping of the metal components of the hybrid nanoparticles without affecting dielectric ones. We apply the developed approach for tuning of the hybrid nanostructures scattering properties in the visible range. The experimental results are supported by molecular dynamics simulation and numerical solving of Maxwell equations., Comment: Published in Advanced Materials

A novel method for single-step, lithography-free, and large-scale laser writing of nanoparticle-based plasmonic structures has been developed. Changing energy of femtosecond laser pulses and thickness of irradiated gold film it is possible to vary diameter of the gold nanoparticles, while the distance between them can be varied by laser scanning parameters. This method has an advantage over the most previously demonstrated methods in its simplicity and versatility, while the quality of the structures is good enough for many applications. In particular, resonant light absorbtion/scattering and surface-enhanced Raman scattering have been demonstrated on the fabricated nanostructures.