Hayrettin Odabasi | Searcharxiv

arXiv2022

Experimental Verification of Illusion Optics with Optical Null Media

We experimentally show the results of the illusion device designed by the transformation optics (TO) technique. The coordinate transformation maps a zero thickness in virtual space to a finite region in physical space, yielding extreme material properties called optical null media (ONM). As a result, an object placed inside the core media will look larger to an outside observer. ONM media is realized using metal-dielectric layered structures in cylindrical coordinates. Also closed-form solutions for the scattering field from a cylindrical object are given in detail to prove illusion effect analytically. ONM media is realized using air and iron sheets in radial structure using effective medium theory. We experimentally fabricate the ONM and show the scattering effect using the ONM. For achieving illusion validation, a metallic pipe has been inserted into the center of the core medium made of Plexiglas and surrounded by ONM.

physics.class-ph↗

arXiv2018

Launching and Controlling Gaussian Beams from Point Sources via Planar Transformation Media

Based on operations prescribed under the paradigm of Complex Transformation Optics (CTO) [1-5], it was recently shown in [5] that a complex source point (CSP) can be mimicked by a parity-time ($\mathcal{PT}$) transformation media. Such coordinate transformation has a mirror symmetry for the imaginary part, and results in a balanced loss/gain metamaterial slab. A CSP produces a Gaussian beam and, consequently, a point source placed at the center of such metamaterial slab produces a Gaussian beam propagating away from the slab. Here, we extend the CTO analysis to non-symmetric complex coordinate transformations as put forth in [6] and verify that, by using simply a (homogeneous) doubly anisotropic gain-media metamaterial slab, one can still mimic a CSP and produce Gaussian beam. In addition, we show that a Gaussian-like beams can be produced by point sources placed {\it outside} the slab as well [6]. By making use of the extra degrees of freedom (real and imaginary part of the coordinate transformation) provided by CTO, the near-zero requirement on the real part of the resulting constitutive parameters can be relaxed to facilitate potential realization of Gaussian-like beams. We illustrate how beam properties such as peak amplitude and waist location can be controlled by a proper choice of (complex-valued) CTO Jacobian elements. In particular, the beam waist location may be moved bidirectionally by allowing for negative entries in the Jacobian (equivalent to inducing negative refraction effects). These results are then interpreted in light of the ensuing CSP location.

physics.optics↗