Enhanced electromagnetic fields within plasmonic nanocavity mode volumes enable multiple significant effects that lead to applications in both the linear and nonlinear optical regimes. In this work, enhanced second‐harmonic generation (SHG) is demonstrated from individual plasmonic nanopatch antennas (NPAs) which are formed by separating silver nanocubes from a smooth gold film using a sub‐10 nm zinc oxide spacer layer. When the NPAs are excited at their fundamental plasmon frequency, a 10⁴‐fold increase in the intensity of the SHG wave is observed. Moreover, by integrating quantum emitters that have an absorption energy at the fundamental frequency, a second‐order nonlinear exciton–polariton strong coupling response is observed with a Rabi splitting energy of 19 meV. The nonlinear frequency conversion using NPAs thus provides an excellent platform for nonlinear control of the light−matter interactions in both weak and strong coupling regimes which will have a great potential for applications in optical engineering and information processing.

Tungsten disulfide (WS2) is a promising two-dimensional material owing to its remarkable optical, electronic, and electrocatalytic behavior. However, morphology of this material varies significantly with growth conditions. In this work, we use salt-assisted low-pressure chemical vapor deposition (LP-CVD) to grow WS2 crystals of a few layers reaching over 50 μm in size on SiO2/Si substrates. We observe a transition from large, dendritic to triangular growth by systematically varying the amount of the NaCl promotor material as well as the presence of intermediate Wx+ states for low NaCl amounts. The transition from dendritic to triangular growth is discussed in the context of diffusion limited aggregation, with the transformation likely being the result of reduced formation energy, owing to increasing concentrations of transition metal oxyhalides for given precursor quantities. These results help to clarify the role of effects of the NaCl precursor in salt-assisted LP-CVD of WS2 and provide a new means to tune the morphology of this material.

NaCl has widely been used as a seeding promoter for chemical vapor deposition of large-scale 2D transition metal dichalcogenides. In this work, we report a study of the influence of NaCl on the growth and optical properties of layered CVD-grown WS2 using steady-state and time-resolved Kerr rotation measurements at room temperature. Strong photoluminescence signals from single flakes grown with a low NaCl content indicates direct band-gap emission, whereas flakes grown with higher amounts of NaCl exhibit red-shifted, weaker photoluminescence. Raman measurements from single flakes also indicate that WS2 grown with higher NaCl amounts result in multilayered structures, while lower NaCl quantities yield monolayer WS2. Ultrafast carrier decay measurements from single flakes also indicate a NaCl-dependent on the valley exchange interaction component (< 10 ps) and slower decay components (> 50 ps), attributed to a combination of phenomena, such as the band gap transitioning from direct to indirect and defect-related localized states. Our study provides insight into the influence of seeding promoters in layered CVD-grown WS2 in particular and 2D transition metal dichalcogenides in general.

Plasmonic nanocavities have proven to be a powerful optical platform for confining light at a length scale much smaller than the diffraction limit. Enhanced electromagnetic fields within the cavity mode volume enable multiple significant effects that lead to applications in both the linear and nonlinear optical regimes. In this work, we demonstrate enhanced second harmonic generation from individual plasmonic nanopatch antennas which are formed by separating silver nanocubes from a smooth gold film using a sub-10 nm zinc oxide spacer layer. When the nanopatch antennas are excited at their fundamental plasmon frequency, a 10^4-fold increase in the intensity of the second harmonic generation wave is observed. Moreover, by integrating quantum emitters that have an absorption energy at the fundamental frequency, a second order nonlinear exciton-polariton strong coupling response is observed with a Rabi splitting energy of 19 meV. The nonlinear frequency conversion using nanopatch antennas thus provides an excellent platform for nonlinear control of the light-matter interactions in both weak and strong coupling regimes which will have a great potential for applications in optical engineering and information processing.

This study examines the 3D attributes of submesoscale eddies identified over a 12-month period within the Western Pacific Ocean. Composite parameters of cyclonic submesoscale eddies (CSMEs) occurring within and away from the Kuroshio Current system are compared and analyzed for their surface and subsurface features, as well as the seasonality of their core properties. Within the Kuroshio Current (KC) region, CSMEs are faster, stronger and deeper than in the open water (OW) region, with composite eddy depths of 97.5 m and 77.5 m, or 2.8 and 2.0 times the mixed layer depth, respectively. Prominent dipolar divergence patterns both at the surface and at depth reveal the presence of ageostrophic influence, with KC CSME cores deviating 48% and OW CSMEs deviating 40% from geostrophic balance at the surface. This imbalance drives strong vertical motion with maximum upward velocities of 19.2 m day⁻¹ at 57.7 m and 9.3 m day⁻¹ at 157.1 m within the KC and OW region CSME cores, respectively. Subsurface extrema analysis reveals structural differences in CSMEs between dynamic regions. These results provide a useful model-based estimate for subsurface CSME features which are difficult to quantify with observations.