Lithography-free near-infrared broadband absorber based on a multilayer nanosystem

Abstract

Broadband absorber has been intensively researched for decades because of its high absorption property which can be applied to various applications. Most designed absorbers are based on metasurfaces with complex surface-patterns and complicate manufacturing processes. In this paper, we propose a lithography-free, simple four-layer dielectric and metal nanosystem as a broadband absorber. The performance of the absorber is demonstrated by both numerical finite difference time domain (FDTD) method and analytical transfer matrix method (TMM). In the concerned wavelength range from 800 nm to 2300 nm, the average absorption is 95.81%. And the two maxima of absorptions are 99.99% at 970 nm and 99.31% at 1708 nm. The broadband absorption is due to the ohmic loss of the material Cr, the reflection of the Al layer, the destructive interference between the Cr and the Al layers, and the top Al2O3 helping much light to enter the absorber. And the simple multilayer absorber does not require precious metals, lithography processes, making a large-scale, low-cost manufacturing process possible.