Optically controlled metamaterial absorbers in the terahetz regime
Seren, Huseyin R.
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Electromagnetic wave absorbers have been intensely investigated in the last century and found important applications particularly in radar and microwave technologies to provide anechoic test chambers, or vehicle stealth. Adding new features such as dynamic modulation, absorption frequency tunability, and nonlinearity, absorbers gain further functions as spatial light modulators, adjustable protective layers, and saturable absorbers which was a key factor in creation of ultra-fast lasers. These efforts required a rigorous search on various materials to find desired behavior. As a rather recent research field Metamaterials (MM) provide an easier path for creation of such materials by allowing engineering the interaction between electromagnetic radiation and materials. Alongside many exotic applications such as invisibility cloaking or negative refraction, MMs also made perfect, or near-unity, absorbers possible. Thanks to their ability to control electric and magnetic responses, by matching the impedance of the MMs to that of free space and simultaneously increasing the losses in the structure, perfect absorption can be achieved. This has been experimentally demonstrated in various bands of electromagnetic spectrum such as microwave, terahertz (THz), infrared, and visible. As in their earlier counterparts, adding modulation and nonlinearity to MM absorbers will broaden their contribution especially in the THz region which is nascent in terms of optical devices such as switches, modulators or detectors. With the recent developments in the THz lasers, THz nonlinear absorbers will be needed to realize ultra-fast phenomena in this region. The main focus of this thesis is incorporating conventional and novel methods to create some of the initial examples of optically controlled MM THz perfect absorbers using microfabrication tools. [TRUNCATED]
Thesis (Ph.D.)--Boston University