Original Article

Epsilon-near-zero ITO/Ag/SiO₂ metamaterial for large nonlinear absorption

¹ State Key Laboratory of Metal Matrix Composites, School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai, 200240, PR China
² Key Laboratory of Atomic and Subatomic Structure and Quantum Control (Ministry of Education), Guangdong Basic Research Center of Excellence for Structure and Fundamental Interactions of Matter, School of Physics, South China Normal University, Guangzhou 510006, PR China
³ China Aerospace Science and Technology Commercial Launch Vehicle Group Co., Ltd, Shanghai, 201109, PR China
⁴ Shanghai Aerospace Equipments Manufacturer Co., Ltd., Shanghai, 200245, PR China

^* e-mail: zy_wang@sjtu.edu.cn
^** e-mail: xiongshuqiang@163.com
^*** e-mail: yhchen@scnu.edu.cn

Received: 30 September 2025
Accepted: 21 November 2025
Published online: 22 December 2025

Abstract

Enhanced nonlinear optical response contributes to higher device efficiency, lower power consumption and more compact integration. In this study, we designed an epsilon-near-zero multilayer metamaterial composed of Ag, ITO and SiO₂. By enhancing the nonlinear optical response of the material at the epsilon-near-zero wavelength, the saturable absorption behavior has been significantly enhanced (β = −3.3 ×  10⁴ cm/GW), which exceeds one order of magnitude when compared to conventional materials such as nanoparticles, two-dimensional materials and so on. Moreover, the strongest nonlinear optical response observed in the annealed multilayer consistently correlates with the redshift of epsilon-near-zero wavelength. Finally, the mechanism underlying saturable absorption is explained through the processes of electronic excitation and relaxation. Our metamaterials can be utilized in saturated absorbers, contributing to the advancement of nonlinear absorption devices.