Reconfigurable Metamaterials for Terahertz Devices




Zepeda-Galvez, Juan Adrian

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The Terahertz (THz) regime of the electromagnetic spectrum comprises the frequencies ranging from 100 GHz to 10 THz. Part of the interest in THz frequencies resides in the saturation of the electromagnetic spectrum, and it has been anticipated that the complete manipulation of signals at THz frequencies could soon reach the stage where the next generation of devices could be developed. Additionally, THz electromagnetic waves exhibit a variety of useful characteristics, namely, they are non-ionizing and most dielectric materials are transparent to them, enabling a wide range of applications, from characterization of chemical substances and quality control to contributions in communications, and conservation of cultural heritage, to name a few. However, the absence of high power THz sources and detectors has led to a drastic performance deterioration of conventional electronic devices and photonic structures when they approach the THz regime, in combination with the scarcity of naturally occurring materials with suitable THz electromagnetic properties, have delayed the demonstration and mass production of THz devices, including dynamically reconfigurable circuitry. One alternative to the aforementioned state of affairs is the utilization of Metamaterials which consist of a periodic array of resonant subwavelength structures such that their periodicity, materials and geometry can tailor the way the material interacts with electromagnetic waves. Thus, the resonant frequency of the Metamaterial array is contingent upon adjustable parameters able to operate even in the THz regime. On the other hand, it has been demonstrated that Cadmium Telluride (CdTe) and Carbon (C) Quantum Dots (QDs) exhibit a reconfigurable behavior in the THz regime in the presence of ultraviolet excitation. Hence, we propose to couple Quantum Dots to a passive Metamaterial array to transform it into a dynamically reconfigurable Metamaterial structure. We will present computational simulations employing the Finite-difference time-domain method (FDTD) to elucidate their potential frequency of operation. In the experimental part, we will describe the Metamaterial array fabrication process and its THz characterization, making use of THz Time-Domain Spectroscopy (THz-TDS) techniques, as well as the synthesis and THz characterization of the CdTe QDs employed in this exercise. Finally, we will demonstrate that a modulation depth of up to 5.02% can be achieved by varying the QDs size and excitation power density.


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Active Metamaterials, Photonic Crystals, Quantum Dots, Terahertz



Physics and Astronomy