Inch-Scale Ball-in-Bowl Plasmonic Nanostructure Arrays for Polarization-Independent Second-Harmonic Generation

Abstract

Second-harmonic generation (SHG) in plasmonic nanostructures has been investigated for decades due to their wide applications in photonic circuit, quantum optics and biosensing. Development of large-scale, uniform, and efficient plasmonic nanostructure system with tunable modes is desirable for their feasible utilizations. Herein, we design an efficient inch-scale SHG source by a solution-processed method instead of traditional high-cost processes. By assembling the gold nanoparticles with the porous anodic alumina templates, multiresonance in both visible and near-infrared regions can be achieved in hexagonal plasmonic nanostructure arrays, which provide strong electric field enhancement at the gap region. Polarizationindependence SHG radiation has been realized owing to the in-plane isotropic characteristic of assembled unit. The tilt-angle dependent and angle-resolved measurement showed that wide-angle nonlinear response is achieved in our device because of the gap geometry of ball-in-bowl nanostructure with nonlinear emission electric dipoles distributed on the concave surface, which makes it competitive in practical applications. Our progress not only makes it possible to produce uniform inch-scale nonlinear arrays through low-cost solution process; and also advances the understanding of the SHG radiation in plasmonic nanostructures.

Nonlinear Light Amplification Governed by Structural Asymmetry

“…Especially for AlNanocap(0°), when the pumping laser is polarized either along the x ‐axis or along the y ‐axis, the SHG response reaches its maximum intensity either at α = 0° (180°) or at α = 90° (270°), suggesting the symmetry of nonlinear responses (Figure 3d). [ 40 ] This analysis of polarization‐resolved SHG responses confirms that observed SHG signals emitted from AlNanocap(0°) primarily originate from the interface‐induced centrosymmetry breaking. [ 11,18 ] Additionally, the decreased asymmetry orientation in AlNanocaps results in the anticlockwise rotation of emission coils for E x (2ω) (Figure 3a–c, upper panel), whereas emission coils for E y (2ω) remain unchanged (Figure 3a–c, bottom panel, highlighted in red double‐headed arrows).…”

Efficient Second‐Harmonic Generation from Silicon Slotted Nanocubes with Bound States in the Continuum

“…With the same pulse energy, a shorter pulse duration would result in a higher SHG efficiency. Enhancing surface SHGs with nanoslots or nanogaps have also been demonstrated in metal plasmonic nanostructures, [49][50][51][52][53][54][55][56][57] such as bow-ties, [49] nanogrooves, [52] and nanocube arrays. [55] Compared with them, the SHG conversion efficiency achieved in our proposed array of Si slotted nanocubes can be several orders of magnitude higher (see Table S1, Supporting Information).…”

Probing Excitonic Rydberg States by Plasmon Enhanced Nonlinear Optical Spectroscopy in Monolayer WS2 at Room Temperature

“…Localized surface plasmon resonance (LSPR) has been known to effectively confine light into the subwavelength region within the near-field of plasmonic metallic nanoparticles or nanocavity, resulting in significantly enhanced local electromagnetic (EM) field . Light–matter interactions can be significantly enhanced due to local electromagnetic field amplification. − By tuning the LSPR mode in resonance with the excitation or emission wavelength of 2D materials, enhanced PL and SHG have been achieved via near-field coupling with plasmonic structures. − As NLO signals are proportional to higher-order power of the incident light, the coupling between LSPR and monolayer TMDs is expected to result in significantly enhanced NLO responses. Furthermore, the excitonic line width of TMDCs could be reduced by coupling with the plasmonic cavity.…”