0.1-20 THz ultra-broadband perfect absorber via a flat multi-layer structure

Area of Science:

• Optics and Photonics
• Materials Science
• Terahertz (THz) Technology

Background:

• Developing efficient broadband absorbers is crucial for various optical and terahertz applications.
• Existing absorbers often struggle with limited bandwidth or angular stability.
• Graded-index mechanisms offer a promising approach for broadband absorption.

Purpose of the Study:

• To design and fabricate an ultra-broadband perfect absorber utilizing a graded-index mechanism.
• To achieve high absorption efficiency over an exceptionally wide frequency range.
• To investigate the angular stability of the designed absorber.

Main Methods:

• Fabrication of a perfect absorber comprising a silicon substrate and a six-layer anti-reflective structure.
• Tuning the refractive index of each layer using hollow polystyrene microsphere and TiO2 nanoparticle dopants.
• Achieving a graded refractive index profile from 1.3 to 2.9.
• Experimental characterization of absorption performance.
• Theoretical simulation for angular stability analysis.

Main Results:

• Experimental demonstration of 98% absorption within the ultra-broadband range of 0.1-20 THz.
• The absorber exhibits a gradually changed refractive index profile.
• Theoretical simulations confirm high absorption efficiency is maintained for incident angles from 0 to 75°.

Conclusions:

• The designed graded-index perfect absorber demonstrates exceptional broadband absorption performance.
• The absorber shows excellent angular stability, making it suitable for diverse applications.
• This work provides a novel platform for advanced terahertz and optical devices.