Doped polymer for low-loss dielectric material in the terahertz range

Daniel Headland,Withawat Withayachumnankul,Daniel Stavrevski,Sharath Sriram,Derek Abbott,Madhu Bhaskaran,Peter Thurgood

doi:10.1364/ome.5.001373

Abstract

The dielectric properties of an elastomeric polymer are modified with the inclusion of dopants, with the aim of reducing dielectric loss in the terahertz range. Polydimethylsiloxane (PDMS) is selected as the host polymer, and micro/nano-particle powders of either alumina or polytetrafluoroethylene (PTFE) are employed as dopants. Composite samples are prepared, and characterised with terahertz time-domain spectroscopy (THz-TDS). The samples exhibit significantly reduced dielectric loss, with a maximum reduction of 15.3% in loss tangent reported for a sample that is 40% PTFE by mass. Results are found to have reasonable agreement with the Lichtenecker logarithmic mixture formula, and any deviation can be accounted for by agglomeration of dopant micro/nano-particles. The new dielectric composites are promising for devising efficient micro-structure components at terahertz frequencies.

Highlights

Elastomeric polymers such as polydimethylsiloxane (PDMS) [1] are often utilised as dielectric materials for terahertz components, owing to their flexibility and compatibility with microfabrication techniques [2,3,4,5]
In this work we present a technique for reducing the dielectric loss of the elastomeric compound PDMS by combining it with low-loss dopants in order to form an artificial medium, with effective properties determined by the intrinsic properties and fractions of the constituent media
The greatest reduction of loss tangent is achieved with the sample that is doped with 40% PTFE by weight

Summary

Introduction

Elastomeric polymers such as polydimethylsiloxane (PDMS) [1] are often utilised as dielectric materials for terahertz components, owing to their flexibility and compatibility with microfabrication techniques [2,3,4,5]. The bio-compatibility of PDMS in particular makes it a suitable candidate for biomedical terahertz applications [16]. Such polymers, have moderate loss in the terahertz range [11,17,18]. It is possible to modify the material properties of a polymer by introducing powder materials, and this technique has been used in the terahertz range to improve the performance of (a) PTFE λ

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