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Dr Georgios Gkantzounis


Research Fellow

Biography

Biography

Georgios Gkantzounis joined the University of Surrey in 2015 as a Research Fellow working on hyperuniform structures. He graduated from the University of Athens, Greece, with a BSc in Physics (2002) with excellence, an MSc in Materials Physics (2004) and a PhD in Photonic Structures (2008) from the University of Athens. Prior to joining the Physics Department at Surrey he worked as a Research Fellow in NCSR Demokritos, Athens Greece (2009-2011) on acousto-optic interactions and as a Research Fellow in California Institute of Technology (2011-2012) on nonlinear elastic dynamics.

Research interests

Current activities are focused on the physics and applications of non-crystallographic band gap materials both for photon and phonon control, lasing in quasi-random (hyperuniform) structures, phononic structures and acousto-optic interactions.

My publications

Publications

Castro-Lopez M, Gaio M, Sellers Steven, Gkantzounis Georgios, Florescu Marian, Sapienza R (2017) Reciprocal space engineering with hyperuniform gold
disordered surfaces,
APL Photonics 2 (6) 061302 AIP Publishing LLC
Hyperuniform geometries feature correlated disordered topologies which follow
from a tailored k-space design. Here, we study gold plasmonic hyperuniform
disordered surfaces and, by momentum spectroscopy, we report evidence of kspace
engineering on both light scattering and light emission. Even if the structures
lack a well-defined periodicity, emission and scattering are directional in
ring-shaped patterns. The opening of these rotational-symmetric patterns scales
with the hyperuniform correlation length parameter as predicted via the spectral
function method.
Gkantzounis Georgios, Amoah Timothy, Florescu Marian (2017) Hyperuniform disordered phononic structures, Physical Review B 95 (9) 094120 American Physical Society
We demonstrate the existence of large phononic band gaps in designed hyperuniform (isotropic) disordered two-dimensional (2D) phononic structures of Pb cylinders in epoxy matrix. The phononic band gaps in hyperuniform disordered phononic structures are comparable to band gaps of similar periodic structures, for both out-of-plane and in-plane polarizations. A large number of localized modes is identi ed near the band edges, as well as, di usive transmission throughout the rest of the frequency spectrum. Very high-Q cavity modes for both out-of-plane and in-plane polarizations are formed by selectively removing a single cylinder out of the structure. E cient waveguiding with almost 100% transmission trough waveguide structures with arbitrary bends is also presented. We expand our results to thin three-dimensional layers of such structures and demonstrate e ective band gaps related to the respective 2D band gaps. Moreover, the drop in the Q factor for the three-dimensional structures is not more than three orders of magnitude compared to the 2D ones.
Gkantzounis Georgios, Florescu Marian (2017) Freeform Phononic Waveguides, Crystals 7 (12)
We employ a recently introduced class of artificial structurally-disordered phononic structures that exhibit large and robust elastic frequency band gaps for efficient phonon guiding. Phononic crystals are periodic structures that prohibit the propagation of elastic waves through destructive interference and exhibit large band gaps and ballistic propagation of elastic waves in the permitted frequency ranges. In contrast, random-structured materials do not exhibit band gaps and favour localization or diffusive propagation. Here, we use structures with correlated disorder constructed from the so-called stealthy hyperuniform disordered point patterns, which can smoothly vary from completely random to periodic (full order) by adjusting a single parameter. Such amorphous-like structures exhibit large band gaps (comparable to the periodic ones), both ballistic-like and diffusive propagation of elastic waves, and a large number of localized modes near the band edges. The presence of large elastic band gaps allows the creation of waveguides in hyperuniform materials, and we analyse various waveguide architectures displaying nearly 100% transmission in the GHz regime. Such phononic-circuit architectures are expected to have a direct impact on integrated micro-electro-mechanical filters and modulators for wireless communications and acousto-optical sensing applications.