Leonid Alekseyev

Optical Hyperlens: Far-field imaging beyond the diffraction limit

We propose an approach to far-field optical imaging beyond the diffraction limit. The proposed system allows image magnification, is robust with respect to material losses and can be fabricated by adapting existing metamaterial technologies in a cylindrical geometry.

Semiclassical theory of the hyperlens

We study ray dynamics inside the hyperlens, a device recently demonstrated as capable of sub-diffraction-limited far-field imaging. The obtained semiclassical result of spiraling rays is confirmed by numerical simulations of Gaussian beam scattering from the hyperlens.

Uniaxial epsilon-near-zero metamaterial for angular filtering and polarization control

We describe a unique class of metamaterials that exhibit strong uniaxial anisotropy with epsilon-zero response along the optical axis and which optical properties depend strongly on polarization. In an example of array of silver nanowires grown in anodic alumina membrane, the proposed singular uniaxial metamaterial is shown to function as a polarizer and narrowband angular transmittance filter.

Slow light and 3D imaging with non-magnetic negative index systems.

We demonstrate that strongly anisotropic planar dielectric systems can be used to create waveguides supporting modes with extremely slow group velocity. Furthermore, we show that such systems can be used for 3D imaging, with a potential for subwavelength resolution.

Midinfrared semiconductor optical metamaterials

We report on a novel class of semiconductor metamaterials that employ a strongly anisotropic dielectric function to achieve negative refraction in the midinfrared region of the spectrum, ∼8.5–13 μm. We present two types of metamaterials, layered highly doped/undoped heterostructures and quantum well superlattices that are highly anisotropic. Contrary to other optical metamaterials these heterostructure systems are optically thick (up to 20 μm thick), planar, and require no additional fabrication steps beyond the initial growth. Using transmission and reflection measurements and modeling of the highly doped heterostructures, we demonstrate that these materials exhibit negative refraction. For the highly doped quantum well superlattices, we demonstrate anomalous reflection due to the strong anisotropy of the material but a determination of the sign of refraction is still difficult. This new class of semiconductor metamaterials has great potential for waveguiding and imaging applications in the long-wave inf...

Strongly anisotropic media: the THz perspectives of left-handed materials

We demonstrate that non-magnetic (μ≡1) left-handed materials can be effectively used for waveguide imaging systems. We also propose a specific THz realization of a non-magnetic left-handed material based on homogeneous, naturally occurring media.

Homogeneous Hyperbolic Systems for Terahertz and Far-Infrared Frequencies

We demonstrate that homogeneous naturally-occurring materials can form hyperbolic media, and can be used for nonmagnetic negative refractive index systems. We present specific realizations of the proposed approach for the THz and far-IR frequencies. The proposed structures operate away from resonance, thereby promising the capacity for low-loss devices.

Super-resolution imaging via spatiotemporal frequency shifting and coherent detection

Diffraction limit is manifested in the loss of high spatial frequency information that results from decay of evanescent waves. As a result, conventional far-field optics yields no information about an objects subwavelength features. Here we propose a novel approach to recovering evanescent waves in the far field, thereby enabling subwavelength-resolved imaging and spatial spectroscopy. Our approach relies on shifting the frequency and the wave vector of near-field components via scattering on acoustic phonons. This process effectively removes the spatial frequency cut-off for unambiguous far field detection. This technique can be adapted for digital holography, making it possible to perform phase-sensitive subwavelength imaging. We discuss the implementation of such a system in the mid-IR and THz bands, with possible extension to other spectral regions.

Semiclassical theory of the Hyperlens

We study ray dynamics inside the Hyperlens, a device recently demonstrated as capable of sub-diffraction-limited far-field imaging. The obtained semiclassical result of spiraling rays is confirmed by numerical simulations of gaussian beam scattering from the hyperlens.

Negative refraction in mid-infrared semiconductor metamaterials

Semiconductor metamaterials consisting of n+-GaInAs/i-AlInAs heterostructures that support negative index modes in the mid-infrared are reported. We demonstrate negative refraction in these metamaterials for wavelengths from 9¿15 ¿m over a wide range of incidence angles.