Electrothermally actuated terahertz metamaterial
Ozturk, Mehmet Saadeddin
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Microelectromechanical Systems (MEMS) have been adapted from Integrated Circuit (IC) technology. MEMS enable fabrication of devices size from a few microns to hundreds of microns. This scale is also a proper scale for Terahertz (THz) metamaterials (MM), which are designed for building homogeneous mediums. Our study aims to demonstrate an operating device which is designed by using mechanical and electromagnetic principles, fabricated by MEMS technology. MEMS actuator and electromagnetic resonator are the two main parts of our device which is called Electrothermally Actuated Metamaterial (ETAMM). Mechanical actuator is realized by using conventional photolithography techniques and THz Time Domain Spectroscopy (TDS) is used for excitation and detection of the resonator. This project is a contribution to the active THz MM devices of which main purpose is to control the optical property by au external stimuli. We aimed to fabricate a tunable THz Metamaterial device. The device is comprised of two mirrored Split Ring Resonator (mSRR) with a certain resonant frequency. Resonance frequency is tuned by electrothermal actuation. As a novel approach, mSRR itself is used as au actuator. Devices nre connected to ectch other through electrodes. They make the current flow through an array and this flow leads to joule heating by causing a thermal expansion of the device. This elastic deformation of the device results as in an out of plane buckling and changes the distance between mSRR and bare silicon substrate. In the electromagnetic part of the mechanism: the change in distance caused by thermal expansion, alters the effective dielectric constant within the gap between the structure and the substrate. Dielectric constant in the gap is the main parameter for resonance frequency, for this reason we chose it as a tuning parameter of the device. In the final analysis, ETAMM utilizes the change in the dielectric constant to alter the resonance frequency. Our device delivered 6 GHz resonance frequency shift as a response to an applied voltage of 5.7V on the device.
Thesis (M.S.)--Boston University
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