Broadband Perfect Absorber Based on TiN-Nanocone Metasurface

Area of Science:

• Plasmonics
• Metasurface optics
• Nanophotonics

Background:

• Development of metasurface perfect absorbers (MPAs) for broadband light absorption is crucial for advanced optical applications.
• Titanium nitride (TiN) is explored as a refractory material for stable and efficient plasmonic devices in the visible-to-near-infrared (NIR) spectrum.

Discussion:

• The finite-difference time-domain (FDTD) method was employed for systematic simulation of MPA absorption.
• Broadband absorption is achieved through localized surface plasmonic resonance (LSPR) in nanocones and gap plasmons, enhanced by resonance coupling.
• The study analyzes electric field intensity and polarization dependence to understand light trapping mechanisms.

Key Insights:

• A TiN nanocone array MPA demonstrates an average absorption of 99.6% across a broad spectrum (400-1500 nm).
• Continuous diameter evolution of TiN nanocones and inter-nanocone gaps contribute to the broadband absorption.
• The MPA maintains high average absorption (~90%) even at oblique incidence angles up to 50 degrees.

Outlook:

• The TiN nanocone array/Al₂O₃/TiN structure shows significant potential for light-trapping applications.
• This MPA design is promising for enhancing efficiency in thermophotovoltaics and other light-harvesting systems.