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

Abstract

Using epsilon-near-zero (ENZ) subwavelength optical multilayer materials with simple structure and thin total thickness to achieve target characteristics is extremely important and beneficial for the realization of on-chip integration and largescale application of optical devices. Combining with the enhanced genetic algorithm (EGA), this work breaks the limitation of the periodicity of traditional ENZ multilayer structures, and investigates the aperiodic ENZ transparent conducting oxide (TCO)-dielectric multilayer structures. It is realized that under the given conditions, an optimal structure can possess a maximum peak absorption and the broadest absorption bandwidth near the communication wavelength. In the 6-layer structure with a total thickness of 600 nm studied in this work, EGA can optimize the peak absorption from 0.91 to 0.95. Additionally, the absorption bandwidth is optimized from 120 nm to 227 nm, which is enhanced more than 180%. The absorption performance of this optimized structure is comparable to that of a more complex structure with the same total thickness but more layers, or a structure with the same number of layers but a larger total thickness. Conclusively, the proposed EGA optimization method can simplify the structure of the multilayer system, reduce the total thickness of the required ENZ material, and thus greatly simplify the production process and reduce the production cost.

Overview of Approaches for Compensating Inherent Metamaterials Losses

“…GA is an artificial intelligence algorithm often utilized to optimize electromagnetic devices in a global sense [137]. The employment of GA for optimizing metamaterials has been fostered in the literature, in particular, to obtain the desired response, such as nearzero constitutive parameters [138], acoustic lens [139], ultrabroadband perfect absorbers [140]. Further, it can determine the number of layers needed for the desired response [141].…”

Optimization of Structural Parameters of PCF Polarization Filter by a Genetic Algorithm

“…After the above three operations, a new population will be generated, and the fitness function will be evaluated repeatedly, and then the population will update again by the three operations. The iterative process is repeated until the population criteria meet a specific index or the set number of iterations is completed [23]. As a consequence, GA will obtain a global optimal solution in research space.…”

Manufacturing-Enabled Tunability of Linear and Nonlinear Epsilon-Near-Zero Properties in Indium Tin Oxide Nanofilms

“…By tuning the real part of permittivity to be a near-zero value at specific wavelengths, ENZ materials can conveniently exhibit a near-zero refractive index n via the formula n = ε μ , , where the permeability can be regarded as a constant for non-magnetic materials, i.e., μ = 1. Hence, they provide a relatively easy way to construct near-zero-index (NZI) materials. − Their near-zero permittivity and refractive index lead to unprecedented optical properties compared to normal dielectric materials, including ultrahigh optical nonlinearity, − large field intensity enhancement (FIE), − better control over light–matter interactions, − and directive emission. − The ENZ materials have become a promising platform to realize extensive linear and nonlinear ultrafast optical applications.…”