Color Gamut Behavior in Epsilon Near‐Zero Nanocavities during Propagation of Gap Surface Plasmons

Abstract

This work reports on numerical and experimental results obtained in plasmonic metal–insulator nanocavities. The systems are composed of silver as metal, and different materials as insulator, namely polyvinylpyrrolidone (PVP), indium tin oxide (ITO), and zinc oxide (ZnO). The proposed nanocavities exhibit extraordinary optical effects as tunable color hue, highlighted in gamut maps, depending on incident/viewing angles, extraordinary transmission and zero reflection at resonant wavelengths, for different incident polarizations. These phenomena are related to the formation of surface plasmon polaritons (SPPs) and gap surface plasmons (GSPs) whose presence is evidenced by a remarkable sigmoidal behavior of the pseudo dielectric function, with epsilon‐near‐zero singularities in its real and imaginary parts. This function is directly calculated from the measured ellipsometric parameters Ψ and Δ and allows probing, in a fast and effective way, the existence of the plasmonic modes. Moreover, in presence of these singularities, the ellispometric analysis of the systems also shows a pronounced dephasing between p‐ and s‐reflected beams that can lead to a Goos–Hänchen shift effect to be exploited for sensing applications. Thanks to their unusual optical properties, the proposed nanocavities open a wide scenario of applications in fields like tunable color filters, optics, photonics, physical security, and sensing.

Leveraging on ENZ Metamaterials to Achieve 2D and 3D Hyper‐Resolution in Two‐Photon Direct Laser Writing

“…The 20× magnified overview of the lens array, reported in Figure 4c, demonstrates the high quality level of the fabrication procedure, whereas the zoom‐in (50×) in the inset of the same figure evidences the morphology homogeneity of the single metalens. The following frames (Figure 4d–f) reflect the peculiar optical functionalities of the metamaterial multilayer [ 24 ] supporting the metalens array: the same metalens is observed through band pass filters (BPF) centered at three different wavelengths, two close to the double ε NZ resonances and one spectrally distant from the others. Through the filter centered at λ BPF = 390 nm (Figure 4d), the structure is very clear and it is even possible to notice horizontal lines in the inner circle of the metalens (Figure 4d).…”

Graphene-based tunable hyperbolic microcavity

“…The practical implementation of our scheme allowed a blue/red shift of the transition wavelength by adjusting the base dielectric thickness or controlling the Fermi level of graphene. The latter is especially effective if accomplished via electrical tuning 53 , 54 . Hence, shifting the transition wavelength further into the IR can be carried out by adopting the lower chemical potential of graphene or a thicker dielectric.…”

Controllable Fast and Slow Light in Photonic-Molecule Optomechanics with Phonon Pump

“…Figure 1 is the photonic-molecule optomechanical system, including two coupled whispering-gallery-mode (WGM) cavities [ 21 , 32 , 53 , 54 , 55 ], where the optomechanical cavity with the decay rate and frequency is evanescently coupled to a tapered fibre. The radiation pressure force arriving from the pump laser field coupled into the optomechanical cavity will induce the radial breathing mode (i.e., the mechanical mode with frequency and damping rate ).…”