Efficient terahertz anti-reflection properties of metallic anti-dot structures

Area of Science:

• Materials Science
• Optics
• Terahertz Technology

Background:

• Conventional metallic thin films used as anti-reflection coatings (ARCs) can suppress primary transmission peaks.
• Metallic films may not optimally manage Fabry-Perot (FP) interference in certain applications.

Purpose of the Study:

• To investigate micrometer-sized copper (Cu) anti-dot structures as novel terahertz (THz) anti-reflection coating (ARC) materials.
• To compare the performance of Cu anti-dot structures with continuous Cu thin films for THz ARC applications.

Main Methods:

• Cu anti-dot structures with varying diameters (100-300 μm) and thicknesses (7-10 nm) were fabricated on silicon substrates using RF magnetron sputtering and e-beam evaporation.
• Anti-reflection performance was evaluated in the terahertz frequency range of 0.3-2.2 THz.

Main Results:

• Cu anti-dot structures demonstrated superior anti-reflection performance compared to continuous Cu thin films.
• Anti-dot arrays reduced both the absolute amplitude of the Fabry-Perot (FP) peak and the amplitude ratio (AR) of the FP peak to the primary peak.
• The anti-reflection performance, specifically the AR, could be tuned by adjusting the anti-dot size.

Conclusions:

• Micrometer-sized Cu anti-dot structures are a promising novel material for terahertz anti-reflection coatings.
• These structures offer enhanced performance by effectively managing FP interference.
• A universal conductivity phase-matching condition was observed, crucial for FP peak suppression.