Enhanced Nonlinear Optical Responses of Layered Epsilon-near-Zero Metamaterials at Visible Frequencies

Abstract

Optical materials with vanishing dielectric permittivity, known as epsilon-near-zero (ENZ) materials, have been shown to possess enhanced nonlinear optical responses in their ENZ region. These strong nonlinear optical properties have been firmly established in homogeneous materials; however, it is as of yet unclear whether metamaterials with effective optical parameters can exhibit a similar enhancement. Here, we probe an optical ENZ metamaterial composed of a subwavelength periodic stack of alternating Ag and SiO2 layers and measure a nonlinear refractive index n 2 = (1.2 ± 0.1) × 10–12 m2/W and nonlinear absorption coefficient β = (−1.5 ± 0.2) × 10–5 m/W at its effective zero-permittivity wavelength. The measured n 2 is 107 times larger than n 2 of fused silica and 4 times larger than the n 2 of silver. We observe that the nonlinear enhancement in n 2 scales as 1/(n 0Re­[n 0]), where n 0 is the linear effective refractive index. As opposed to homogeneous ENZ materials, whose optical properties are dictated by their intrinsic material properties and hence are not widely tunable, the zero-permittivity wavelength of the demonstrated metamaterials may be chosen to lie anywhere within the visible spectrum by selecting the right thicknesses of the subwavelength layers. Consequently, our results offer the promise of a means to design metamaterials with large nonlinearities for applications in nanophotonics at any specified optical wavelength.

Ultrafast Nonlinear Pulse Propagation Dynamics in Metal–Dielectric Periodic Photonic Architectures

“…[7] Suresh et al also reported nonlinear optical features in the strongly absorbing region (at 2.48 eV) of (Ag (16 nm)/ SiO 2 (65 nm)) 5 type metamaterial with nonlinear absorption coefficient of (−)1.5 × 10 −5 m W −1 . [15]…”

“…The ultrafast dynamics and the higher-order nonlinearities of MD metamaterials are dominated by the contribution of metal's noninstantaneous Kerr nonlinearity [15][16][17][18][19] and several numerical studies have been carried out in 1D and cylindrical type 2D geometries for the specific spectral region of interest. [16,17] Especially, the numerical realization of the ultrafast pulse propagation in wavelength-ordered multilayer MD structure is not straight forward because of a large variety of spatial and temporal effects, ranging from self-focusing and self-phase modulation to the formation of solitons.…”

Optimization of Epsilon-Near-Zero Multilayers for Near-Perfect Light Absorption Using an Enhanced Genetic Algorithm

“…ENZ photonics has attracted extensive attention in recent years, which is considered as a new platform for integrating photonic and nanophotonic devices [9]- [12]. In combination with ENZ materials, a variety of optical metamaterials and devices with different functions have been designed based on hollow waveguide structures [13], [14], grating structures [10], [15], [16], multilayer structures [17], [18] and complex hybrid structures [19], [20].…”

“…Multilayer structure is one of the most common methods to realize an effective ENZ point [17]. It follows the effective medium theory (EMT) [21] to achieve near-zero permittivity with metal-dielectric or TCO-dielectric alternating structures.…”

“…It follows the effective medium theory (EMT) [21] to achieve near-zero permittivity with metal-dielectric or TCO-dielectric alternating structures. ENZ multilayer structures have many advantages, such as the ability to adjust the ENZ wavelength by changing the type of materials or changing the thickness proportion of different materials [17]. Through the designing of the multilayer structures, the enhancement of nonlinear optical effects [22], controlling of plasma resonance [20], modulation of material absorption [23]- [26], and ultra-fast optical tuning [27] have been realized.…”