Energy loss of terahertz electromagnetic waves by nano-sized connections in near-self-complementary metallic checkerboard patterns

TL;DR

This study investigates how nano-sized connections in near-self-complementary metallic checkerboard patterns cause broadband, frequency-independent energy loss in terahertz waves, highlighting the roles of finite conductivity and randomness.

Contribution

It provides experimental and numerical insights into energy loss mechanisms in nano-scale metallic connections within self-complementary patterns, revealing the breakdown of perfect conductor approximation.

Findings

Finite conductivity causes broadband absorption at nano-scale connections.

Randomness in connections enhances energy loss through scattering.

Approaching perfect self-complementarity leads to spontaneous breakdown of perfect conductor approximation.

Abstract

The design of a self-complementary metallic checkerboard pattern achieves broadband, dispersion-less, and maximized absorption, concentrating in the deep subwavelength resistive connections between squares, without any theoretical limitation on the energy absorbing area. Here, we experimentally and numerically investigate the electromagnetic response in the limit of extremely small connections. We show that finite conductivity and randomness in a near-self-complementary checkerboard pattern plays a crucial role in producing a frequency-independent energy loss in the terahertz frequency region. Here metals behave like an almost perfect conductor. When the checkerboard pattern approaches the perfect self-complementary pattern, the perfect conductor approximation spontaneously breaks down, owing to the finite conductivity at the nano- scale connection, leading to broadband absorption. It is also shown that the random connections between metallic squares also lead to broadband and maximized energy loss through scattering loss, similar to finite conductivity.