Shahram Dehdashti

Panoramic lens designed with transformation optics

The panoramic lens is a special kind of lens, which is applied to observe full view. In this letter, we theoretically present a panoramic lens (PL) using transformation optics method. The lens is designed with inhomogeneous and anisotropic constitutive parameters, which has the ability to gather light from all directions and confine light within the visual angle of observer. Simulation results validate our theoretical design.

Bifunctional acoustic metamaterial lens designed with coordinate transformation

We propose a method to design bifunctional acoustic lens using acoustic metamaterials that possess separate functions at different directions. The proposed bifunctional acoustic lens can be implemented in practice with subwavelength unit cells exhibiting effective anisotropic parameters. With this methodology, we experimentally demonstrate an acoustic Luneburg-fisheye lens at operational frequencies from 6300 Hz to 7300 Hz. Additionally, a bifunctional acoustic square lens is proposed with different focal lengths for multi directions. This method paves the way to manipulating acoustic energy flows with functional lenses.

Manipulating surface plasmon polaritons with infinitely anisotropic metamaterials

Guiding surface states through disorders recently has attracted attention of scientists from diverse backgrounds. In this work, we report a robust method to guide surface plasmon polaritons (SPPs) through arbitrary distorted metal surfaces (a kind of disorder), including slopes, bumps, and sharp corners. Almost total transmissions over a broad frequency range can be achieved by use of infinitely anisotropic metamaterials (IAMs). The SPPs are coupled into and out of the bulk modes in the IAMs, where the bulk modes are routed by altering the principle axis of the IAMs. Due to unique non-diffraction property of the IAMs, all processes are of high efficiency, which are explained from both microscopic and macroscopic perspectives. Several functional SPP devices, including adapter, cloak, and sharp bending waveguide, are presented in the simulations. Two proof-of-concept SPP devices are experimentally demonstrated, where the SPPs are mimicked by the designer SPPs at microwave frequency.

Curvature detection by entanglement generation using a beam splitter

In this paper, we investigate the behavior of radiation field, whose state is described by the so-called sphere coherent state, through a beam splitter. These states are realization of coherent states of two-dimensional harmonic oscillator, which lives on a sphere, as radiation field. By using the linear entropy as a measure of entanglement, we show that the entanglement depends on the curvature of the sphere. So, by using the appropriating sphere coherent states, we can control the entanglement of the output states of the beam splitter in the laboratory. In addition, as the convince measures of non-classical behaviors, we consider Mandel parameters of the output states of the beam splitter and their quadrature squeezing.

Non-contact method to freely control the radiation patterns of antenna with multi-folded transformation optics

In this paper, we propose to use multi-folded transformation optics method to design a non-contact illusion device that can distantly and freely manipulate the radiation behavior of antenna located at a certain distance and such manipulation is enabled by the use of mapped electromagnetic medium coated with the transformed medium. The proposed design aims to achieve the radiation pattern of our choice from the antenna that does not possess any electromagnetic medium. Based on this, the functionality of parabolic antenna is distantly achieved from the point source. We further extended our idea to array of antennas in which the proposed device distantly makes the linear array of antennas behave like a geometrically different array of antennas. Our work extends the concept of illusion optics for active scatterer that will be very helpful for future antenna design.

Magnetized Plasma as a Versatile Platform for Switching

We study the magneto-permittivity effect in a magnetized plasma with appropriately designed parameters. We show that at frequencies near the plasma frequency, magneto-optical activity plays an important role to manipulate and control the wave propagations in the magnetized plasma. Such a unique feature can be utilized to establish sensitive magnetic field switching mechanism, which is confirmed by detailed numerical investigations. Switching by magnetic field based on magnetized plasma is flexible and compatible with other optical system; moreover it is applicable to any frequency by tuning the plasma density. For these reasons, our work shows the possibility for developing a new family of high frequency and ultrasensitive switching applications.

Role of intertwined Hamiltonian in two dimensional classical optics

Intertwined Hamiltonian formalism originally has its roots in quantum field theory and non-relativistic quantum mechanics. In this work, we develop the non-relativistic two dimensional intertwined Hamiltonian formalism in classical optics. We obtain the properties of the intertwined media in detail and show that the differential part of intertwining operator is a series in Euclidean algebra generators. Also, we investigate quadratic gradient-index medium as an example of this structure, and obtain the intertwining operator and intertwined medium refractive index. Moreover, we study the preservation of quantum properties in the intertwined medium. For this, we consider superposition preservation as the most important property of quantum characters. We show that when a Schrodinger cat state is generated in gradient-index medium, we can construct another Schrodinger cat state in the intertwined one.

Realization of non-linear coherent states by photonic lattices

In this paper, first, by introducing Holstein-Primakoff representation of α-deformed algebra, we achieve the associated non-linear coherent states, including su(2) and su(1, 1) coherent states. Second, by using waveguide lattices with specific coupling coefficients between neighbouring channels, we generate these non-linear coherent states. In the case of positive values of α, we indicate that the Hilbert size space is finite; therefore, we construct this coherent state with finite channels of waveguide lattices. Finally, we study the field distribution behaviours of these coherent states, by using Mandel Q parameter.

Conformal mapping in hyperbolic metamaterial: Application of two-dimensional Clifford algebra

In this paper, we begin with the metric which describes the propagation of the extraordinary ray in the hyperbolic metamaterials as the following: ds² = -c²dt²+ε₀dr²+ε_er²dΦ²+ε₀dz², equation in which ε_o > 0 and ε_e <; 0. We are interested in the z = const and also rescale the radial coordinate by ρ = √ε_or such that ds²=-c²dt²+dp²+dp²-γ²dp²dφ which γ² = |ε_e/ε_o|. By considering the coordinate transformation X = ρ cosh γφ and Y = ρ sinh γφ, we can rewrite the above metric as: ds²=-c²dt²+dX²-dY² equation which is so-called ultrahyperbolic metric. We indicate that, by applying the two-dimensional Clifford algebra, z = X + jY, which the hyperbolic number j saturates j² = 1, we can rewrite the ultrahyperbolic metric as: ds²=-c²dt²+dzdz* in which z* = X-jY, in the Kline disk. By defining the conformal mapping, which indeed is the map between two Kline disk we can investigate behaviour of light in the conformal hyperbolic metamaterial, in the level of ray optics. Also, in the framework of the wave optics, which the Klein-Gordon equation describes the behaviour of light, by applying the abovementioned conformal mapping and using the Clifford algebra, we can obtain the light propagation in the framework of the wave optics for conformal hyperbolic metamaterials. Moreover, by using this concept, we stablish a connection between the conformal field theory and classical optics.

CURVED SPACE-TIME FOR LIGHT BY AN ANISOTROPIC MEDIUM: MEDIA WITH THE VARIABLE OPTICAL AXES

An optical impedance-matched medium with a gradient refractive index can resemble a geometrical analogy with an arbitrary curved space-time. In this paper, we show that a non-impedancematched medium with a varying optical axis can also resemble the features of a space of non-trivial metric for the light. The medium with a varying optical axis is an engineered stratified slab of material, in which the orientation of the optical axis in each layer slightly differs from the other layers, while the magnitude of refractive index remains constant. Instead of the change in refractive index, the inhomogeneity of such a medium is induced by the local anisotropy. Therefore, the propagation of light depends on the local optical axis. We study the conditions that make the analogy between curved spacetime and a medium with a varying optical axis. Extension of the transformation optics to the media with optical axis profile might ease some fabrication difficulties of materials with gradient refractive index.