Controlling metamaterial resonances via dielectric and aspect ratio effects

Abstract

We study ways to enhance the sensitivity and dynamic tuning range of the fundamental inductorcapacitor (LC) resonance in split ring resonators (SRRs) by controlling the aspect ratio of the SRRs and their substrate thickness. We conclude that both factors can significantly affect the LC resonance. We show that metafilms consisting of low height SRRs on a thin substrate are most sensitive to changes in their dielectric environment and thus show excellent potential for sensing applications.There has been intense interest in metamaterials in the past decade, and a number of intriguing effects, such as negative refraction [1], electromagnetic cloaking [2] and sub-wavelength focusing [3] have been experimentally demonstrated. More recently, much research has been focused on demonstrating metamaterials which can be used for practical applications. For example, resonance frequency agility was demonstrated in a metafilm by tuning the conductivity of a patterned silicon substrate [4]. This allows for applications such as dynamically tunable notch filters. A metamaterial solid state phase modulator for terahertz radiation has also been demonstrated [5]. Metamaterials have also been studied for sensing applications, where the shift in the resonance frequency upon the application of a dielectric film over the metamaterial is exploited [6][7][8][9].The ability to control and optimize the size of the resonance frequency shift in metamaterials can offer some advantages for practical applications. It can lead to greater sensitivity for detection purposes or to greater dynamic range for applications such as filters. Recently, there has been some interest in fabricating metamaterials on thin membranes like Silicon Nitride [10,11] and Parylene [12]. Such flexible metafilms enable layering schemes and conformal placement onto curved surfaces, thus allowing even greater potential for applications. It is also believed that such metafilms will be more sensitive. In one case, the metamaterial showed sensitivity to the presence of a single atomic layer of graphene on its surface [10]. This sensitivity results because thin substrates lower the effective permittivity of the supporting medium and allow simple transmission measurements due to lower loss. There is thus strong motivation to study how a metamaterial on thin, flexible substrate differ from those on thicker substrates.In this work, we will study the effects of the substrate thickness and aspect ratio on the properties of fundamen- * Electronic address: phybaa@nus.edu.sg tal inductor-capacitor (LC) resonance in the Split Ring Resonator (SRR). In particular, we want to establish if thinner substrates can indeed offer advantages like enhanced sensitivity compared to thick substrates. We will also study the effect of SRR aspect ratio on the resonance. In a previous work, we showed the advantage of using high aspect ratio SRRs fabricated using the Proton Beam writing technique (electron micrograph in Fig. 1(b)). We showed that on thick substrates, high aspect ratio SRRs offered incre...

A Compact Thin-Film Sensor Based on Nested Split-Ring-Resonator (SRR) Metamaterials for Microwave Applications

“…By CMP (Chemical Mechanical Planarization), standard photolithography and wet etching process, both SRR structures are fabricated on a 500 μm thick Rogers RT5880 substrate with the relative dielectric constant of ε r =2.2 and loss tangent of tgδ= 0.0009. To reduce the operated frequency, the metallic copper thickness is only 2 μm, which is thinner than the previously designed parameter, since the operated frequency of the SRR based on a thick substrate increases as the SRR thickness increases [22]. Descriptions of other parameters for a nested SRR and traditional SRR structures are shown in Fig.…”

Terahertz Sensing Application by Using Fractal Geometries of Split-Ring Resonators

“…In [22,23], the direct write technique called proton beam writing (PBW) was used to fabricated high aspect ratio SRRs. In [24,25], MTMs were fabricated on ultra-thin silicon nitride substrates.…”

A Dual-Mode Terahertz Filter Based on a Metallic Resonator Design

“…Based primarily on the design of planar array metallic resonators, both spectral filters [1][2][3][4][5] and thin-film sensors [6,7] have been demonstrated. Interestingly, the quality of the resonant response of these planar devices can be adjusted by controlling the aspect ratio and substrate thickness of the structure [8], or by introducing asymmetry to the underlying structure [3,4].…”