Second harmonic generation hotspot on a centrosymmetric smooth silver surface

Abstract

Second harmonic generation (SHG) is forbidden for materials with inversion symmetry, such as bulk metals. Symmetry can be broken by morphological or dielectric discontinuities, yet SHG from a smooth continuous metallic surface is negligible. Using non-linear microscopy, we experimentally demonstrate enhanced SHG within an area of smooth silver film surrounded by nanocavities. Nanocavity-assisted SHG is locally enhanced by more than one order of magnitude compared to a neighboring silver surface area. Linear optical measurements and cathodoluminescence (CL) imaging substantiate these observations. We suggest that plasmonic modes launched from the edges of the nanocavities propagate onto the smooth silver film and annihilate, locally generating SHG. In addition, we show that these hotspots can be dynamically controlled in intensity and location by altering the polarization of the incoming field. Our results show that switchable nonlinear hotspots can be generated on smooth metallic films, with important applications in photocatalysis, single-molecule spectroscopy and non-linear surface imaging.

Second Harmonic Generation for Moisture Monitoring in Dimethoxyethane at a Gold-Solvent Interface Using Plasmonic Structures

“…For this purpose, we used triangular plasmonic cavities milled in Au thin film which have been reported to give rise to significant and measurable SHG responses [26,27]. If close enough, those cavities can undergo coupling and the SHG response is dramatically enhanced, as reported earlier [26][27][28][29][30][31].…”

“…For this purpose, we used triangular plasmonic cavities milled in Au thin film which have been reported to give rise to significant and measurable SHG responses [26,27]. If close enough, those cavities can undergo coupling and the SHG response is dramatically enhanced, as reported earlier [26][27][28][29][30][31]. The interaction between the adsorbate and the plasmonic cavities can alter the coupling between the cavities and the overall susceptibility at the interface, allowing us to measure small events occurring on the metallic surface.…”

Pronounced Linewidth Narrowing of Vertical Metallic Split-Ring Resonators via Strong Coupling with Metal Surface

“…Plasmonic and metamaterial structures allow the coherent oscillations of free electrons, known as surface plasmons [ 1 , 2 , 3 ]. The resonant excitation of the localized surface plasmon resonances (LSPRs) and propagating surface plasmon polaritons (SPPs) concentrates light into subwavelength volumes and induces large electric field enhancements, known as ”hot spots”, which can be exploited in potential applications such as sensing [ 4 , 5 ], nonlinear optics [ 6 , 7 ], optical switching [ 8 , 9 ], photodetection [ 10 , 11 ], and solar energy absorbers [ 12 , 13 ] and related devices. Meanwhile, significant efforts have also been taken to explore nanostructures which are capable of providing localized magnetic enhancements [ 14 , 15 , 16 , 17 , 18 ].…”

Plasmon enhanced second harmonic generation by periodic arrays of triangular nanoholes coupled to quantum emitters

“…6 Although linear optics of plasmonic materials is still of great interest, the nonlinear optical phenomena greatly enhanced by surface plasmon resonances are fast emerging. [7][8][9][10][11][12] Beyond metallo-dielectric nanoconstructs and their properties are exciton-plasmon materials involving molecular assemblies and plasmonic systems. [13][14] Under certain conditions when the coupling strength between molecules and local electromagnetic field associated with the plasmon resonance exceeds all dissipation rates, such a system enters the strong coupling regime.…”