The ability of light to carry and deliver orbital angular momentum (OAM) in the form of optical vortices has attracted much interest. The physical properties of light with a helical wavefront can be confined onto two-dimensional surfaces with subwavelength dimensions in the form of plasmonic vortices, opening avenues for thus far unknown light-matter interactions. Because of their extreme rotational velocity, the ultrafast dynamics of such vortices remained unexplored. Here we show the detailed spatiotemporal evolution of nanovortices using time-resolved two-photon photoemission electron microscopy. We observe both long- and short-range plasmonic vortices confined to deep subwavelength dimensions on the scale of 100 nanometers with nanometer spatial resolution and subfemtosecond time-step resolution. Finally, by measuring the angular velocity of the vortex, we directly extract the OAM magnitude of light.

We report light emission around 1200 nm from a vertical heterostructure consisting of M0S2 and WSe2 monolayers. The emission, arising from the fundamental interlayer exciton, can be tuned by nearly 100 nm by electrical gating.

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In contrast to the more common nitrogen-vacancy (NV) center in diamond, the SiV possesses bright narrow band and spectrally stable optical transition concentrated (70% of the fluorescence) in its zero phonon line (ZPL) protected by inversion symmetry, even at room temperature. [4,5] Despite these attractive characteristics, some properties hinder the SiV applicability: short coherence times (nanosecond scale), limited mainly by coupling to the thermal acoustic phonon bath [6] and low extraction efficiency from the high-index diamond substrate. Different methods for mitigating these issues have been investigated in recent years, [1,[7][8][9][10] but currently there is no apparent approach to exploit the SiV superb optical properties at room temperature and at the same time to increase its photon outcoupling without compromising its optical quality and coherence. The use of nanodiamonds or nanostructures prepared by a top-down approach can mitigate the issue of total internal reflection within the diamond, but at the same time may introduce additional decoherence [11] and optical instability mechanisms attributed to poor surface quality (surface defects containing spins, charge traps, nondiamond phases, surface termination of atoms and groups [12] ) as a result of the synthesis or structuring process. The SiVs can be formed in the diamond host via ion implantation of silicon ions [1,13] or by introducing silicon atoms from a solid or gas precursor during the growth stage of diamond layers. [14,15] The latter is considered to better preserve the quality of the diamond layer by avoiding implantation damages and promoting a smaller amount of vacancy clusters and nonradiative sites which can otherwise hinder the SiV applicability. Herein, the ability to sculpt nanostructures by a bottom-up approach enables the creation of higher quality complex structures that are not accessible via top-down fabrication techniques. [16][17][18] In particular, this concerns the fabrication of highly confined and deterministic nanostructures hosting an atom-like system that maintain the original substrate quality -a critical prerequisite for quantum information and sensing applications. Here, we present a robust and deterministic template-assisted bottom-up process for the creation of high-quality nanoscale diamond pyramids incorporating SiVs.The negatively charged silicon-vacancy center (SiV) in diamond is a potential high-quality source of single-indistinguishable photons for quantum information processing and quantum electrodynamics applications. However, when embedded in bulk diamond, this emitter suffers from both, relatively low extraction efficiency attributed to total internal reflection as well as nondeterministic location. On the other hand, its implementation in nanodiamonds is impeded by optical dephasing owing to their degraded surface quality. Here a robust and deterministic template-assisted bottom-up process for the creation of high-quality diamond nanopyramids incorporating SiVs is reported. This method employs a predefi...

We introduce and demonstrate a new approach for nitrogen-vacancy (NV) patterning in diamond, achieving a deterministic, nanometer-thin, and dense delta-doped layer of negatively charged NV centers in diamond. We employed a pure nitridation stage using microwave plasma and a subsequent in situ diamond overgrowth. We present the highest reported nitrogen concentration in a delta-doped layer (1.8 × 10 20 cm −3 ) while maintaining the pristine diamond crystal quality. This result combined with the large optically detected magnetic resonance contrast can pave the way toward highly sensitive NV-based magnetometers. We further employed this delta-doping technique on high-quality fabricated diamond nanostructures for realizing a topographic NV patterning in order to enhance the sensing and hyperpolarization capabilities of NV-based devices.