Polarization controller based on embedded optical transformation

Design of a Low-Reflection Flat Lens Antenna Based on Conformal Transformation Optics

In this paper, a wideband flat lens antenna with low reflection and good performance is presented based on conformal transformation optics (CTO). Physical space optimization is applied to eliminate singular refractive index values. Furthermore, we employ the optical path rescaling method to enhance the sub-unity refractive indices and to reduce reflection. Therefore, an implementable all-dielectric isotropic medium is obtained. The final flat lens profile comprises six layers with a constant permittivity value in each layer. Simulation results of the three-dimensional structure indicate that the designed flat lens operates in a wide frequency bandwidth. The flat lens antenna has an S₁₁ value of less than -15 dB in the frequency range of 13 to 30 GHz. The proposed lens was designed and simulated using COMSOL Multiphysics, and radiation performance results were validated using the CST Studio Suite. The simulated radiation pattern shows that the side lobe level is less than -16.5 dB in two simulation software programs, and the half-power beam width varies from 5.6° to 2.7° with increasing frequency. Moreover, the simulated antenna gain is about 28.3-35.5 dBi in the 13-30 GHz frequency range.

Omnidirectional polarization beam splitter for white light

As a key element in optical systems, a broadband and omnidirectional polarization beam splitter has been long desired. Here, based on anisotropic metamaterials, a perfect polarizing beam splitter is theoretically designed for the extremely broad frequency and angle bands without energy loss. When an electromagnetic wave is incident on the beam splitter, the transverse magnetic-polarized component suffers total reflection, while the transverse electric-polarized component is completely transmitted within the incident angle range [-90°, 90°] for the white light. This study provides a new approach to design an efficient polarizing beam splitter and may promote the development and applications of anisotropic metamaterials.

Transformation bending device emulated by graded-index waveguide

We demonstrate that a transformation device can be emulated using a gradient-index waveguide. The effective index of the waveguide is spatially varied by tailoring a gradient thickness dielectric waveguide. Based on this technology, we demonstrate a transformation device guiding visible light around a sharp corner, with low scattering loss and reflection loss. The experimental results are in good agreement with the numerical results.

Achieving laser ignition using zero index metamaterials

The possibility of laser ignition using zero index metamaterials (ZIM) is investigated theoretically. Using this method, multiple laser beams can be focused automatically regardless of the number and location of electromagnetic sources in the ZIM, and it is not necessary to aim all beams at the focus. Our calculation shows that although the size of the focus is dependent on the wavelength, the beams can be focused to a tiny spot. Methods for achieving practical performance are proposed.

Arbitrary waveguide connector based on embedded optical transformation

Arbitrary connector for waveguides of different cross sections is proposed and designed theoretically based on the embedded optical transformation theory. First, the general expressions of constitutive tensors of the metamaterials filled in the connector are derived. Second, there are some full-wave simulations that validate the constitutive tensors derived. The results show that the connector with metamaterials inclusions with designed constitutive parameters can fulfill the reflectionless transmission of electromagnetic waves between waveguides of different cross sections. Finally, connectors of several forms are investigated parametrically, and two sets of constitutive tensors that can be physically achieved by existing metamaterials are gotten. It is believed that this study provides a feasible way to fulfill the efficient transmission of electromagnetic waves between waveguides of different cross sections.

Transformation optics and metamaterials

Underpinned by the advent of metamaterials, transformation optics offers great versatility for controlling electromagnetic waves to create materials with specially designed properties. Here we review the potential of transformation optics to create functionalities in which the optical properties can be designed almost at will. This approach can be used to engineer various optical illusion effects, such as the invisibility cloak.