Actively tunable terahertz electromagnetically induced transparency analogue based on vanadium-oxide-assisted metamaterials

Abstract

Recently, phase-change materials (PCMs) have drawn more attention due to the dynamically tunable optical properties. Here, we investigate the active control of electromagnetically induced transparency (EIT) analogue based on terahertz (THz) metamaterials integrated with vanadium oxide (VO2). Utilizing the insulator-to-metal transition of VO2, the amplitude of EIT peak can be actively modulated with a significant modulation depth. Meanwhile the group delay within the transparent window can also be dynamically tuned, achieving the active control of slow light effect. Furthermore, we also introduce independently tunable transparent peaks as well as group delay based on a double-peak EIT with good tuning performance. Finally, based on broadband EIT, the active tuning of quality factor of the EIT peak is also realized. This work introduces active EIT control with more degree of freedom by employing VO2, and can find potential applications in future wireless and ultrafast THz communication systems as multi-channel filters, switches, spacers, logic gates and modulators. Keywords: terahertz metamaterials; phase-change materials; vanadium oxide; electromagnetically induced transparency 1. Introduction Over the past decades, Metamaterials (MMs) have been focused continually due to the capability to manipulate electromagnetic (EM) waves in an unnatural way [1]. By designing artificial meta-resonators of MMs and arranging them appropriately, MMs can tailor lightwaves in subwavelength scale, consequently providing optical responses with desirable properties. In recent years, MMs have come to the terahertz (THz) regime [2]. Located between infrared and microwave band, THz radiations have enjoyed a rise of interest and are promising for security scanning [3], future wireless communications as well as the sixth-generation (6G) networks [3-5]. Now, MMshave been regarded as ideal platforms to achieve chipscale THz devices, such as THz sources [6,7], modulators [8,9], sensors [10,11] and absorbers [12,13].Recently, electromagnetically induced transparency (EIT) analogue in THz MMs have attracted more attention [14][15][16]. EIT refers to a sharp transparent window within a broad absorption spectrum, which comes from the quantum interference between two distinct excitation pathways in the natural three-level atom system [17]. Due to the dispersion properties, EIT has potential applications in slow light, optical data storage, nonlinear process enhancement and signal processing [18]. Mimicking EIT in the classical system, MMs can reproduce such effect via the near-field coupling between bright and dark modes supported on meta-resonators [14]. Compared with the conventional EIT, which requires severe experimental conditions [18], MM-based EIT analogue is easier to be produced and more stable, therefore suitable for practical chipscale applications [15].At the same time, for THz communication systems, THz devices with active tunability are required [19]. Therefore, various active optical materials have been utilized to turn passive MMs...

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