Control of Resonance Absorption Modes for Broadband Infrared Metamaterial Absorber

Magnetic polariton resonance, standing wave, and their coupling have provided interesting and exotic characteristics for infrared metamaterial. In this paper, the metal-insulator-metal metamaterial absorbers consisting of either single layer dielectric or bilayer dielectrics are discussed to reveal the geometric and dielectric thin film control of resonance absorption modes. These absorption modes can be independently manipulated by specific geometrical parameters, and thus provide a multi-peak characteristic for the metamaterial absorber. Comparing to the single dielectric structure, a new freedom of modes control is introduced to the bilayer dielectric structure by the addition of low epsilon MgF2, and then results in a quasi-continuous broadband absorption in the range of 5-8 mu m. Experimental result further demonstrates the broadband effect, consistent with the numerical simulation.