Browsing by Subject "Negative refractions"

Now showing 1 - 5 of 5

Open Access
Experimental study of subwavelength focusing by lefthanded metamaterials with a negative refractive index
(2007) Özbay, Ekmel; Aydin, K.
Two dimensional (2D) left-handed metamaterials (LHM) exhibiting negative refraction and subwavelength imaging are studied experimentally. A left-handed transmission band is observed at the frequencies where both dielectric permittivity and magnetic permeability are simultaneously negative. 2D LHM structure is verified to have a negative refractive index by measuring the refraction through a prism-shaped sample. Subwavelength focusing is observed by using a flat LHM superlens.
Open Access
Hybrid plasmon-phonon polariton bands in graphene-hexagonal boron nitride metamaterials [Invited]
(Optical Society of America, 2017) Hajian, H.; Ghobadi, A.; Dereshgi, S. A.; Butun, B.; Özbay, Ekmel
We theoretically investigate mid-infrared electromagnetic wave propagation in multilayered graphene-hexagonal boron nitride (hBN) metamaterials. Hexagonal boron nitride is a natural hyperbolic material that supports highly dispersive phonon polariton modes in two Reststrahlen bands with different types of hyperbolicity. Due to the hybridization of surface plasmon polaritons of graphene and hyperbolic phonon polaritons of hBN, each isolated unit cell of the graphene-hBN metamaterial supports hybrid plasmon-phonon polaritons (HPPs). Through the investigation of band structure of the metamaterial we find that, due to the coupling between the HPPs supported by each unit cell, the graphene-hBN metamaterial can support HPP bands. The dispersion of these bands can be noticeably modified for different thicknesses of hBN layers, leading to the appearance of bands with considerably flat dispersions. Moreover, analysis of light transmission through the metamaterial reveals that this system is capable of supporting high-k propagating HPPs. This characteristic makes graphene-hBN metamaterials very promising candidates for the modification of the spontaneous emission of a quantum emitter, hyperlensing, negative refraction, and waveguiding. © 2017 Optical Society of America.
Open Access
The magical world of metamaterials
(IEEE, 2009-10) Özbay, Ekmel
In recent years, there has been a burgeoning interest in rapidly growing field of metamaterials due to their unprecedented properties unattainable from ordinary materials. Veselago pointed out that a material exhibiting negative values of dielectric permittivity (ε) and magnetic permeability (μ) would have a negative refractive index [1]. Generally speaking, the dielectric permittivity (ε) and the magnetic permeability (μ) are both positive for natural materials. In fact it is possible to obtain negative values for ε and μ by utilizing proper designs of metamaterials. Left-handed electromagnetism and negative refraction are achievable with artificially structured metamaterials exhibiting negative values of permittivity and permeability simultaneously at a certain frequency region. The first steps to realize these novel type of materials were taken by Smith et al., where they were able to observe a left-handed propagation band at frequencies where both dielectric permittivity and magnetic permeability of the composite metamaterial are negative [2]. Soon after, left-handed metamaterials with an effective negative index of refraction are successfully demonstrated by various groups [3].
Open Access
Negative refraction and focusing by a left-handed material slab in free space
(IEEE, 2006) Aydın, Koray; Özbay, Ekmel
Negative refraction and focusing by a left-handed metamaterial (LHM) slab are experimentally verified. We measured refractive index of slab as -1.86. The flat lens behavior of LHM is demonstrated for two different point source distances. © 2006 Optical Society of America.
Open Access
Negative refraction and subwavelength focusing using left-handed composite metamaterials
(SPIE, 2008-01) Özbay, Ekmel; Aydın, Koray
We review experimental studies performed on left-handed metamaterials (LHM) at microwave frequencies. The metamaterial structure is composed of periodic arrays of split-ring resonators and wire meshes and exhibits a left-handed propagation band at frequencies of negative permittivity and negative permeability. Negative refraction is verified using prism shaped LHM and also by beam-shifting method. Subwavelength focusing of a point source is achieved with a resolution of 0.13λ, through a flat LHM superlens.