Electric-field tuning of a planar terahertz metamaterial based on strained SrTiO<inf>3</inf> layers

We demonstrate a metamaterial exhibiting a frequency-tunable response in the terahertz domain, controlled by a bias electric field. The active part of the metamaterial consists of a periodic metallic pattern deposited on a thin epitaxially strained strontium titanate film. The role of the metallic structure is two-fold: it gives rise to the metamaterial resonance and it enables applying an electric bias to the strontium titanate layer. The strained film exhibits a pronounced dependence of its permittivity on the bias, which exerts a strong influence on the resonance. Specifically, the resonance of our structure occurs near 0.5 THz and, upon applying a bias voltage of 55 V, a relative tunability of the resonance frequency of 19% was achieved at room temperature.