Micro/nano electromagnetic devices for tuning, metamaterials, and plasmonics

Interesting macroscopic electromagnetic phenomena across microwave, terahertz, and optical frequencies can be achieved by controlling the electromagnetic properties of materials at micro- and nano-scale level. Harnessing micro- and nano-scale fabrication techniques to realise high-resolution structures that enable such explorations is the focus of this thesis.

Micro- and nano-structures operating from microwave to visible frequencies have been realised on both rigid and flexible elastomer substrates. These structures enable a wide variety of phenomena and applications. The focus is on developing innovative fabrication solutions for electromagnetic devices. Innovations are derived from integrating a lab-on-a-chip pneumatic device, microfabrication of high-resolution resonator structures on rigid substrates and elastomeric polydimethylsiloxane (PDMS), electron-beam lithography (EBL) to realise nanopatterns, and device applications.

Major contributions of this thesis include a micromechanical switch that can be operated pneumatically to demonstrate a first bias-voltage-free switching, sub-wavelength resonators realised on PDMS substrate with the potential for tuning metamaterials by elastic deformation, high Q-factor resonators realised on low-loss rigid planar substrates to demonstrate terahertz metamaterials with strong-field enhancements, and to realise high-resolution dielectric resonator antenna to manipulate visible light.

A process has been established to realise high-resolution microscale patterns on elastomeric PDMS substrate. This fabrication technique has enabled novel integration of coplanar waveguide with a pneumatic valve to demonstrate switching of RF transmission line with greater than 20 dB isolation between its “on” and “off” states. Further, the fabrication technique has been extended to realise sub-wavelength resonators operating at terahertz frequencies to demonstrate tuning by mechanical deformation, with greater than 8% resonance frequency tuning with repeatable results over several stretching-relaxing cycles. Terahertz metamaterials with high-Q resonances is realised using microfabrication processes to demonstrate novel plasmonic phenomena. Coaxial micro-cavities and complementary split-ring resonator designs are investigated to demonstrate terahertz localised surface plasmon resonances and spoof surface plasmon polaritons, respectively. High-resolution nanostructures have been realised using EBL to demonstrate a first all-dielectric optical antenna, this low-loss optical antenna is used to impart a beam deflection of 19.9° at 633 nm, with the deflection angle dependent upon its sub-array geometry.