Iryna Khodasevych

Elastomeric silicone substrates for terahertz fishnet metamaterials

In this work, we characterize the electromagnetic properties of polydimethylsiloxane(PDMS) and use this as a free-standing substrate for the realization of flexible fishnet metamaterials at terahertz frequencies. Across the 0.2–2.5 THz band, the refractive index and absorption coefficient of PDMS are estimated as 1.55 and 0–22 cm−1, respectively. Electromagnetic modeling, multi-layer flexible electronics microfabrication, and terahertz time-domain spectroscopy are used in the design, fabrication, and characterization of the metamaterials, respectively. The properties of PDMS add a degree of freedom to terahertz metamaterials, with the potential for tuning by elastic deformation or integrated microfluidics.

Reconfigurable Fishnet Metamaterial Using Pneumatic Actuation

The design, fabrication and measurement of a reconflg- urable flshnet metamaterial based on a new method of tuning by chang- ing unit cell geometry is reported. Retractable elements are added to the unit cell utilizing pneumatically actuated switching. It is shown that the pneumatic actuation approach can unite a number of metallic elements into a complex conducting structure. Experimental demon- stration conflrms that the structure operates at two difierent frequen- cies in the GHz range in distinct actuation states. The measured results also show good agreement with numerical simulations.

Pneumatically switchable graded index metamaterial lens

A low-profile pneumatically switchable graded index metamaterial lens operating at 9 GHz is proposed and practically demonstrated. An effective graded refractive index is engineered using an array of electric resonators of differing resonant frequency. Normal orientation of the resonators allows ultrathin single metamaterial layer lens design. Switching between focusing and non-focusing states is practically demonstrated by shorting the gaps in split ring resonators and eliminating the resonant response and the phase difference between the elements across the lens with pneumatically actuated metal patches that are pressed against the gaps of the resonators as the pressure in the chamber is reduced.

Nonlinear microwave metamaterial resonators using gravitational restoring force realized on a microfabricated perforated substrate

We demonstrate microwave metamaterial with enhanced nonlinearity enabled by a significant mass and loss reduction due to perforated SU-8 substrate supporting self-rotating split ring resonators utilizing gravity as a restoring force. Forces involved in resonator movement are analyzed, and mechanical features of the structure are optimized. Unconventional microfabrication technique allowing creation of metal coated SU-8 structures with non-coincident metal and substrate patterns is introduced, resulting in a robust micrometer sized mesh. The beneficial effects of perforated substrate are demonstrated on electromagnetic properties of single resonators as well as coupled nonlinear resonator pair. Improvement in quality factor of single resonator as a result of reduced substrate mesh density is shown in the microwave frequency range. Nonlinear resonant frequency shift by 0.067 GHz is achieved for a pair of coupled resonators upon increasing the microwave power from 1 mW to 1 W.

Flexible fishnet metamaterial on PDMS substrate for THz frequencies

We present the design of a flexible fishnet metamaterial on a PDMS substrate operating at terahertz (THz) frequencies. The low-cost, flexibility and low-surface energy of PDMS enables a range of possible sensing applications.

Experimental demonstration of two-dimensional hybrid waveguide-integrated plasmonic crystals on silicon-on-insulator platform

Nanoscale plasmonic structures can offer unique functionality due to extreme sub-wavelength optical confinement, but the realization of complex plasmonic circuits is hampered by high propagation losses. Hybrid approaches can potentially overcome this limitation, but only few practical approaches based on either single or few element arrays of nanoantennas on dielectric nanowire have been experimentally demonstrated. In this paper, we demonstrate a two dimensional hybrid photonic plasmonic crystal interfaced with a standard silicon photonic platform. Off resonance, we observe low loss propagation through our structure, while on resonance we observe strong propagation suppression and intense concentration of light into a dense lattice of nanoscale hot-spots on the surface providing clear evidence of a hybrid photonic plasmonic crystal bandgap. This fully integrated approach is compatible with established silicon-on-insulator (SOI) fabrication techniques and constitutes a significant step toward harnessing plasmonic functionality within SOI photonic circuits.

Tunable split ring resonators using air pressure

A novel method of controlling the resonant frequency of broadside coupled split ring resonators using air pressure is proposed. The broadside coupled split ring resonators consist of a static ring and a dynamic floating ring located above it. Resonant frequency shifting is realized by adjusting gap between two split rings, which is dependent on the air pressure applied. Measurements and theoretical simulations show the efficacy of the gap tuning and corresponding resonant shift.

Mesh substrate for gravitational magnetoelastic metamaterial

In this paper we present a microfabricated mesh substrate for use in gravitational magnetoelastic metamaterials. The high resolution technique allows the manipulation of the electromagnetic properties of the substrate towards free space-like performance. This is achieved via removal of predetermined substrate areas while simultaneously shaping the required mechanical features.

Switchable graded index microwave metamaterial lens design using pneumatic actuation

We propose the design of graded index metamaterial lens using pneumatic actuation for switching between focusing and non focusing states and operating at 9 GHz. Graded refractive index is engineered by using split ring resonators of different widths. Choice of electrical resonators allows planar design and significantly reduced thickness of the lens. Switching between focusing and non focusing states is based on shortening the gaps in split ring resonators with pneumatically actuated metal patches. This leads to the disappearance of the resonant response of split rings and flattening of phase difference between the elements across the lens. The concept is demonstrated by fabrication and measurement of two versions of the lens representing focusing and non focusing states.