Dynamically tunable terahertz ultra-wideband absorber based on a photosensitive silicon ring-coupled structure.

Area of Science:

• Optoelectronics
• Metamaterials
• Nanophotonics

Background:

• Traditional phase-change material absorbers face challenges in structural complexity and dynamic tuning.
• The terahertz (THz) spectrum requires advanced absorption and reflection devices for various applications.
• Photosensitive materials offer a pathway for dynamic control in optical devices.

Purpose of the Study:

• To design and demonstrate a dynamically tunable terahertz ultra-wideband absorber.
• To overcome limitations of traditional absorbers by utilizing a photosensitive silicon structure.
• To achieve flexible control over absorption and reflection characteristics in the THz range.

Main Methods:

• A periodic array design featuring a square-ring-circular coupling structure was proposed.
• A three-dimensional resonant system was formed using a polycyclic olefin copolymer dielectric and a gold film.
• Photosensitive silicon conductivity was modulated by adjusting pump light power to tune device response.

Main Results:

• Achieved >90% absorption in the 1.83-4.07 THz range at high photosensitive silicon conductivity (1.5×10^5 S/m).
• Exhibited >95% total reflection at low conductivity (1.0×10^3 S/m), demonstrating a bistable response.
• Showcased polarization insensitivity due to structural symmetry and a maximum absorption modulation depth of 94.61%.

Conclusions:

• The proposed photosensitive silicon ring-coupled structure enables dynamic tunability of terahertz absorption.
• The device exhibits polarization insensitivity and a remarkable bistable absorption/reflection response.
• Potential applications include stealth technology, high-resolution imaging, and 6G communication systems.