Microfabricated functional terahertz reflectarrays and metamaterials

Electromagnetic devices operating from microwave to visible frequencies have already been realised to demonstrate a wide variety of applications. However, intriguing electromagnetic phenomena across the terahertz frequencies are yet to be unveiled. Terahertz radiation typically refers to the electromagnetic spectrum spanning 0.1-10 THz, which translates to a wavelength range of 3 mm-0.03 mm. This spectral band bridging the worlds of electronics and optics has been relatively unexplored and is referred to as ‘terahertz gap’ because of accessibility difficulties. <br><br>Metamaterials are artificial composite structures with tailored electromagnetic response. They are assemblies of multiple individual elements fashioned from conventional microscopic materials. This new class of materials dramatically adds a degree of freedom to the control of electromagnetic waves. The emergence of metamaterials coincides with the emerging interest in terahertz radiation (T-rays), for which efficient forms of electromagnetic manipulation are being sought. Metamaterials are of particular interest in the terahertz regime, where most natural materials exhibit only weak electric and magnetic responses and hence cannot be utilized for controlling the radiation.<br><br>Beyond the terahertz frequencies, the fabrication of metamaterials can be very challenging with present technologies. This thesis emphasizes on implementing and experimentally demonstrating innovative fabrication solutions for micro-scale metamaterials designed to operate in the terahertz electromagnetic regime. Microfabrication is a conventional fabrication technique that has been employed to fabricate metamaterials operating at terahertz frequencies. A variety of terahertz components based on terahertz metamaterials have been proposed in this thesis- perfect absorbers, quarter-wave plates, half-wave plates to name a few. A process has been established to realise subwavelength resonators demonstrating polarisation beam splitting operation at terahertz frequencies. Micro-cavities have been investigated to demonstrate terahertz localised surface plasmon resonances in perfect absorbers. Metamaterial-inspired split ring resonators have been realised as polarisation convertor for terahertz radiations. Microfabrication techniques have been devised to achieve combined polarization-dependent functions of reflective deflection and transmission through a single structure.