Nonlinear Dielectric Nanoantennas and Metasurfaces: Frequency Conversion and Wavefront Control

Abstract

High-index dielectric nanostructures can support optical resonances of electric and magnetic character with ultralow linear absorption. In contrast to plasmonics, they can be engineered to confine electromagnetic fields inside the resonator, amplifying intrinsic nonlinearities of the dielectric. In this Review I examine the ability of dielectric nanoantennas and metasurfaces for efficient harmonic generation and wave-mixing processes, as well as nonlinear wavefront manipulation of the incident and radiated light. A detailed comparison is made between the many nanoscopic dielectric configurations reported in the literature, evaluating the influence of the material, crystal symmetry, structure geometry, and the different resonances involved (electric and magnetic Mie modes, Fano resonances, and quasi-nonradiative states, including anapoles and quasi-bound states in the continuum). The nonlinear performance of the nanosystems is analyzed, with emphasis on frequency conversion efficiency and emission directionality control, also discussing recent advances in nonlinear imaging, nonlinear holography, and all-optical switching. The role of topology in nonlinear nanophotonics is reviewed in the end, and potential future directions in the field are laid out.

Nonlinear optics with structured light

“…Excellent reviews can be found in ref. 145,147,148 . They are structured by definition and can combine wavelength conversion with wavefront control 149−151 , spin-orbit interactions 152 , OAM operations involving SAM 143 , image encoding 153 and optical activity 154 .…”

Boosting second-harmonic generation in the LiNbO3 metasurface using high- Q guided resonances and bound states in the continuum

“…Consequently, all-dielectric nanoparticles with high refractive indices, large nonlinear coefficients, and low losses have been used in building enhanced optical nonlinear processes over the past few years. Such nanoparticles support Mie resonances which enable the enhanced harmonic generations, including second-harmonic generation (SHG), third-harmonic generation (THG), and four-wave mixing (FWM) [14][15][16][17][18][19][20][21][22]. Mie-type resonances can provide strong local field confinement inside the nanostructure and thus enhance the nonlinear conversion efficiency from the resonant nanostructures [23,24].…”

Efficient Frequency Conversion with Geometric Phase Control in Optical Metasurfaces

“…However, introducing all‐dielectric nanostructures made of high refractive index materials with strong nonlinear coefficients allows us to boost the nonlinear conversion efficiency by several orders and introduce certain functionalities. [ 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 ] These high index nanostructures support diverse spatial electromagnetic modes to couple the nonlinear coefficients of the material to the external electromagnetic field. Two important categories of these modes in the context of nonlinear optics are the Mie modes and the bound states in the continuum (BIC).…”