New degrees of freedom in nonlinear metamaterials

Abstract

This is an overview of the recent achievements in exploiting novel degrees of freedom in metamaterial design, which enable sophisticated nonlinear coupling mechanisms and bring enhancement to nonlinear behavior. One of the novel paradigms makes use of mechanical feedback, achieved by embedding electromagnetic resonators within elastic medium or engineering explicit elastic links between them, such as rotational feedback. These designs provide broad‐band self‐adjustable resonances, self‐oscillations, chaotic regimes, nonlinear chirality and, spontaneous chiral symmetry breaking. With this respect, a range of implementations has been analyzed, from flexible helices for microwaves to artificial electrostriction in optics. Another concept benefits from multi‐frequency operation, where the properties in completely distinct frequency ranges become entangled through specific metamaterial design –for example, direct optical coupling can be introduced between microwave resonators, providing an independent interaction channel. It was also found that hyperbolic metamaterials can bring notable benefits to classical nonlinear processes by imposing unusual phase matching solutions, with a rich choice of matching combinations. Finally, the boundary structure of metamaterials add yet another possibility to control their properties. Overall, the recent progress in these topics suggests a very positive outlook into the future of nonlinear metamaterials.

Nonlinear symmetry breaking in photometamaterials

“…(A7) into Eq. (A4) and separating the equations for the different powers of ζ , we obtain a set of linear differential equations with the unknown functions Q (1) , Q (2) , and Q (3) , respectively. We further evaluate the magnetic moment of the meta-atom as m = Q S/c and extract the relevant polarizabilities:…”

“…The flourishing field of nonlinear metamaterials [1][2][3] provides a wide variety of ways to implement artificial structures with unusual functionalities [4] including magnetoelastic metamaterials [5][6][7], bistable and self-tunable structures [8][9][10], metamaterials with nonlinear response tuned by the external static field [11][12][13], and metamaterials exhibiting an interplay of electric and magnetic-type nonlinearities [14,15].…”

Energy localization, Fano resonances, and nonlinear meta-optics

“…However, metamaterials can exhibit nonlinear magnetic response resulting in a new type of magnetic nonlinearities [32]. This picture is at large adapted in the microwave regime, and a vast number of research groups are engaged in utilizing tailored nonlinear response of metamaterials, as discussed in the recent review papers [33,34]. However, the idea of generic magnetic nonlinearities remains distant to the nonlinear optics community, while new direct observations of the effects induced by magnetic response are being reported, as discussed below.…”

Considerably Enhanced Second-Harmonic Generation in Resonant U-Shaped Nano-Structures

“…Besides, plasmonic resonances of these structures are utilized for other kind of applications such as switches for optical information processing [12]. Strong confinement of the electromagnetic fields on the nano-scale is another feature of the plasmonic resonant structures which allow significant enhancement of weak nonlinear processes [13], [14]. This can be applicable for increasing the nonlinearity of the metal itself or 14 of a material adjacent to the metal [14]- [16].…”