Low-loss terahertz metamaterial from superconducting niobium nitride films

C H Zhang,B B Jin,J B Wu,J Chen,M Tonouchi,L Kang,W W Xu,P H Wu,Z M Ji

doi:10.1364/oe.20.000042

Abstract

This paper reports a type of low Ohmic loss terahertz (THz) metamaterials made from low-temperature superconducting niobium nitride (NbN) films. Its resonance properties are studied by THz time domain spectroscopy. Our experiments show that its unloaded quality factor reaches as high as 178 at 8 K with the resonance frequency at around 0.58 THz, which is about 24 times that of gold metamaterial at the same temperature. The unloaded quality factor keeps at a high level, above 90, even when the resonance frequency increases to 1.02 THz, which is close to the gap frequency of NbN film. All these experimental observations fit well into the framework of Bardeen-Copper-Schrieffer theory and equivalent circuit model. These new metamaterials offer an efficient way to the design and implementation of high performance THz electronic devices.

Highlights

Metamaterials (MMs) consisting of artificial metallic structure elements have achieved exotic electromagnetic phenomena, such as artificial magnetism[1], negative refractive index 2, superfocusing 3-4 and extraordinary transmission[5], which are absent in natural materials
Theoretical studies have shown that the surface resistance of YBCO increases with frequency more rapidly that that of Cu does
We present a low ohmic loss superconducting THz MM made from superconducting niobium nitride (NbN) film, which has higher fg (≈1.2 THz) than Nb 15

Summary

Introduction

Metamaterials (MMs) consisting of artificial metallic structure elements have achieved exotic electromagnetic phenomena, such as artificial magnetism[1], negative refractive index 2, superfocusing 3-4 and extraordinary transmission[5], which are absent in natural materials. As the frequency is pushed higher towards to terahertz (THz), this loss will increase greatly and have a large negative impact on the realization of exotic electromagnetic phenomena.

Results

Conclusion