Magnetically tunable zero-index metamaterials

TL;DR

This paper introduces a magnetically tunable zero-index metamaterial using YIG pillars, demonstrating dynamic control over electromagnetic properties and enabling applications in tunable devices with low loss.

Contribution

The work presents the first magnetically tunable ZIM with dynamic modulation capabilities in the microwave regime, utilizing the Cotton-Mouton effect of YIG.

Findings

Successfully toggled between gapless and bandgap states

Achieved tunable supercoupling with low loss and high extinction ratio

Demonstrated phase transition between zero-index and negative phase

Abstract

Zero-index metamaterials (ZIMs) feature a uniform electromagnetic mode over a large area in arbitrary shapes, enabling many applications including high-transmission supercouplers with arbitrary shapes, direction-independent phase matching for nonlinear optics, and collective emission of many quantum emitters. However, most ZIMs reported till date are passive, with no method for the dynamic modulation of their electromagnetic properties. Here, we design and fabricate a magnetically tunable ZIM consisting of yttrium iron garnet (YIG) pillars sandwiched between two copper clad laminates in the microwave regime. By harnessing the Cotton-Mouton effect of YIG, the metamaterial was successfully toggled between gapless and bandgap states, leading to a "phase transition" between a zero-index phase and a single negative phase of the metamaterial. Using an S-shaped ZIM supercoupler, we experimentally demonstrated a tunable supercoupling state with a low intrinsic loss of 0.95 dB and a high extinction ratio of up to 30.63 dB at 9 GHz. Our work enables dynamic modulation of the electromagnetic characteristics of ZIMs, enabling various applications in tunable linear, nonlinear, quantum and nonreciprocal electromagnetic devices.