Open AccessUltra-broadband coherent perfect absorption via elements with linear phase response
Author(s) -
Hao Zhang,
Haifeng Zhang
Publication year - 2022
Publication title -
optics express
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.394
H-Index - 271
ISSN - 1094-4087
DOI - 10.1364/oe.471906
Subject(s) - optics , terahertz radiation , molar absorptivity , absorption (acoustics) , electromagnetic radiation , materials science , broadband , phase response , total internal reflection , optoelectronics , physics , phase (matter) , quantum mechanics
Increasing interest in perfect absorption of metasurface has initiated a discussion on the implementation of ultra-broadband coherent perfect absorption (CPA). Here, we present a mirror symmetric coherent absorption metasurface (CAMS) with polarization independence based on resistive thin films and annular metal patterns to force the fulfillment of ultra-broadband CPA in terahertz (THz) regime, controlling the interplay between electromagnetic waves and matter. By incorporating internal and external ring-shaped films with attached phase-delay lines, the desired phase response can be obtained, laying the foundation for implementing ultra-broadband coherent absorption. Simultaneously, by building a metal-medium composite structure superseding the dielectric substrate, additional promotion of the coherent absorptivity over the operation frequencies is realized. Manipulating the phase difference of two back-propagation coherent beams, the coherent absorptivity at 8.34-25.07 THz can be tailored successively from over 95.7% to as low as 38.1%. Moreover, with the incident angle up to 70° for the transverse electric wave, the coherent absorptivity is still over 74.8% from 8.34 THz to 25.07 THz. And for the transverse magnetic wave, at 6.67-24.2 THz, above 81.3% coherent absorptivity is visible with the incident angle increased from 0° to 60°. Our finding provides an interesting approach to designing ultra-broadband coherent absorption devices and may serve applications in THz modulators, all-optical switches, and signal processors.