Photonic crystals as host material for a new generation of microwave components (original) (raw)
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Microwave lens design using two-dimensional 12-folded quasi-photonic crystals
2008
Two-dimensional quasi-photonic crystal as microwave focusing element is studied. The proposed structure is a random square-triangle tiling system with 12-fold symmetry and, hence, 12-fold symmetry quasi crystal. For this structure, finite difference time domain for illustration of focusing of the electromagnetic wave is used and results show that with suitable selection of crystal structure output signal is exactly the same as input one. The effective index of considered structure is near to -1. This situation is useful for small spatial dispersion that is necessary for focusing.
Efficient Focusing with an Ultra-Low Effective-Index Lens Based on Photonic Crystals
MRS Proceedings, 2005
This work focuses on photonic crystals (PC) that can be ascribed an effective index of refraction > 1 or even > 0. We investigate the possibility to design optical elements (in this case a lens) based on this type of PC. A new approach for determining the effective refractive index of PCs with unusual index of refraction is used, which is simpler than earlier methods based on analyzing equi-frequency surfaces in k-space. An ultra-low refractive index PC is given a form approximating a concave lens and is proven theoretically and experimentally that it efficiently focuses the electromagnetic radiation in the microwave range. Strong focusing effects are found for both polarizations (TE and TM mode). Intensity gains as large as 35 for TM polarizations and 29 for TE polarizations are found. Measurements are in a good accordance with simulations.
Light focusing via Rowland concave surface of photonic crystal
Applied Physics Letters, 2007
This letter investigates the focusing characteristics of lightwaves emitted from photonic crystal waveguide aperture using a concave corrugated surface. Based on Rowland's theory, the concave structure is applied to the photonic crystal output surface. The field distribution pattern of the emitted lightwaves demonstrates the focusing effect. The focusing distance agrees with Rowland's theory. By optimizing the surface structures, the focused beam has a full wave at half maximum width of 1.6a. This suggests that the concave corrugated surface could substitute conventional optical lens for focusing and coupling subwavelength devices. Similarly, by inverting the surface structures, the lightwaves splits at the same focusing location.
Microwave Applications of Photonic Crystals
Progress in Electromagnetics Research-pier, 2003
We have demonstrated guiding and bending of electromagnetic (EM) waves in planar and coupled-cavity waveguides built around three-dimensional layer-by-layer photonic crystals. We observed full transmission of the EM waves through these waveguide structures. The dispersion relations obtained from the experiments were in good agreement with the predictions of our waveguide models. We also reported a resonant cavity enhanced (RCE) effect by placing microwave detectors in defect structures. A power enhancement factor of 3450 was measured for planar cavity structures. Similar defects were used to achieve highly directional patterns from monopole antennas.
Progress In Electromagnetics Research, 2008
A three dimensional plano-convex lens which is placed at a certain distance from a plane uniaxial interface has been considered. High frequency fields refracted by the geometry are derived. The treatment is based on Maslov's method. The method combines the simplicity of asymptotic ray theory and generality of the transform method to remedy the problem of geometrical optics around the caustic point of a focusing system. Field patterns are obtained which includes the observation points around the caustic region. The results are found in good agreement with obtained using Huygens-Kirchhoff Principle.
Design & Analysis of Optical Lenses by using 2D Photonic Crystals for Sub-wavelength Focusing
International Journal of Advanced Computer Science and Applications, 2012
2D Photonic lenses (Convex-Convex, Convex-Plane, Plane-Convex, Concave-Concave, Concave-plane, and Plane-Concave) have been designed, simulated and optimized for optical communication using FDTD method. The effect of Crystal structures (Rectangular, Hexagonal, Face centered Cubic (FCC), Body centered Cubic (BCC), variation lattice constant (Λ), hole radius(r), reflective index (n), is demonstrated to get optimized parameters. Finally, with optimized parameters the effect of variation of lens radius on focal lengths and Electrical Field Intensity (Ey) is analyzed. Like optical lens, the focal length of photonic lens is also increased with lens radii, has dependency on optical axis. Moreover, with optimized parameters, Concave-Concave lens have been found as an optimal photonic lens that show sub-wavelength focusing with spatial resolutions-9.22439μm (Rectangular crystal), 7.379512μm (Hexagonal Crystal), 7.840732μm (FCC, BCC).
Comprehensive analysis of two different graded-index photonic-crystal lenses
Ukrainian Journal of Physical Optics, 2017
We investigate two alternative approaches for implementing graded-index (GRIN) photonic-crystal (PC) structures that reveal a focusing effect. Gradient of the refractive index is achieved either using a symmetry-reduction approach (a structure of type I) or varying a filling fraction of PC elements (a structure of type II). We test the first structure for the frequencies located inside the first and second bands of the dispersion diagram. The focusing effect of the first structure characteristic for the frequencies located above the bandgap is stronger than that for the frequencies below the bandgap. It is demonstrated that variations of filling fractions of the elliptical air holes in the structure of type II produce a GRIN lens that manifests a pronounced focusing effect. We have also compared the focusing effects of the latter structure for the TE and TM polarizations. The both structures suggested in the present work can work in a broad enough band region.
Towards focusing using photonic crystal flat lens
Opto-Electronics Review, 2006
We report on the numerical simulation and fabrication of a two-dimensional flat lens based on negative refraction in photonic crystals. The slab acting as a lens is made of an hole array (operating at the wavelength of 1.5 μm) etched in a InP/InGaAsP/InP semiconductor layer. We first study the key issues for the achievement of a negative refractive index taking advantage of folding of dispersion branches with main emphasis in dispersion properties rather than the opening of forbidden gaps. The diffraction and refraction regimes are analysed according to the comparison of the wave-vector with respect to the relevant dimensions of the hole array. In the second stage, we illustrate technological challenges in terms of e-beam lithography on a sub-micron scale and deep reactive ion etching for an indium phosphide based technology.
Measurements of a prototype 20 GHz metamaterial flat lens
2019
In this paper, we present measurements of a prototype metamaterial flat lens. Flat, lenses with short focal lengths are of particular interest due to their potential use in quasi-optical observing in space-based cubesat applications. Our metamaterial flat lens was manufactured by using 11 layers of RO3003 circuit board laminate with etched sub-wavelengthsized copper patterning. The copper patterning is designed in such a way as to maximize the transmittance of the lens while applying the correct phase shift across the lens plane to give the lens its focusing properties. The lens was measured by scanning a receiver horn through one axis of the image plane of a transmitting horn. This measurement demonstrated that the waist of the focused gaussian beam is 30% wider than ideal. It is suspected that this non-ideality is caused by phase error in the design process, though simulations would be necessary to confirm this. Further measurements will be useful to fully characterize the lens’s ...