Suchergebnisse

Metamaterials and metastructures with effective relative permittivity near zero exhibit unusual wave properties such as uniform phase distributions across such domains. Here we discuss the possibility of using ε-near-zero (ENZ) metamaterials for lensing and Fourier transforming. Owing to the possibility of having ENZ metamaterials in different wavelength regimes, the concepts shown here can be utilized at any frequency bands in which such materials can be constructed. ; The authors acknowledge fruitful discussion with Mario Silveirinha from the Department of Electrical Engineering—Instituto de Telecomunicaç̃oes, University of Coimbra, Portugal. Effort sponsored by the Army Research Laboratory and the Air Force Office of Scientific Research, Air Force Material Command, USAF, under Grant No. FA8655-10-1-3078, and by the Spanish Government under contract Consolider "Engineering Metamaterials" CSD2008-00066.M.N.-C. acknowledges support from UPNA Mobility Grant 2010.

Optical forces allow manipulation of small particles and control of nanophotonic structures with light beams. While some techniques rely on structured light to move particles using field intensity gradients, acting locally, other optical forces can push particles on a wide area of illumination but only in the direction of light propagation. Here we show that spin orbit coupling, when the spin of the incident circularly polarized light is converted into lateral electromagnetic momentum, leads to a lateral optical force acting on particles placed above a substrate, associated with a recoil mechanical force. This counterintuitive force acts in a direction in which the illumination has neither a field gradient nor propagation. The force direction is switchable with the polarization of uniform, plane wave illumination, and its magnitude is comparable to other optical forces. ; This work has been supported, in part, by EPSRC (UK). A.V.Z. acknowledges support from the Royal Society and the Wolfson Foundation. N.E. acknowledges partial support from the US Office of Naval Research Multidisciplinary University Research Initiative Grant No. N00014-10-1-0942. A.M. acknowledges support from the Spanish Government (contract Nos TEC2011-28664-C02-02 and TEC2014-51902-C2-1-R). ; Rodríguez Fortuño, FJ.; Engheta, N.; Martínez Abietar, AJ.; Zayats, AV. (2015). Lateral forces on circularly polarizable particles near a surface. Nature Communications. 6(8799):1-7. https://doi.org/10.1038/ncomms9799 ; S ; 1 ; 7 ; 6 ; 8799 ; Novotny, L. & Hecht, B. Principles of Nano-Optics Cambridge University Press (2011). ; Jackson, J. D. Classical Electrodynamics Wiley (1998). ; Ashkin, A. & Dziedzic, J. M. Optical levitation by radiation pressure. Appl. Phys. Lett. 19, 283 (1971). ; Ashkin, A. Acceleration and trapping of particles by radiation pressure. Phys. Rev. Lett. 24, 156–159 (1970). ; Omori, R., Kobayashi, T. & Suzuki, A. Observation of a single-beam gradient-force optical trap for dielectric particles in air. Opt. Lett. 22, ...

Graded index ε near-zero (GRIN-ENZ) quasi-optical components such as beam steerers and power splitters are designed, simulated and analyzed. The GRIN-ENZ medium is realized using stacked narrow hollow waveguides whose infinite array shows the first transmission peak at 1.0002 THz. Several GRIN-ENZ beam steerers to channel a normal incident plane wave to different output angles (15, 45, 65 and 80 deg) with good impedance matching (low reflection) are analytically and numerically demonstrated using planar structures with a thickness of 5λ0 = 1500 μm along z-axis. Moreover, symmetrical and asymmetrical power splitters are designed with output angles (plus/minus 45 deg) and (-80, +35 deg), respectively. ; This work was supported in part by the Spanish Government under contract Consolider Engineering Metamaterials CSD2008-00066 and contract TEC2011-28664-C02-01. V.P.-P. is sponsored by Spanish Ministerio de Educación, Cultura y Deporte under grant FPU AP-2012-3796. V.T. is sponsored by the Universidad Pública de Navarra. M.B. is sponsored by the Spanish Government via RYC-2011-08221. M. N.-C. is supported by the Imperial College Junior Research Fellowship.

The following article appeared in Pacheco-Peña, V., Torres, V., Orazbayev, B., Beruete, M., Sorolla, M., Navarro-Cía, M., & Engheta, N. (2014). Mechanical 144GHz beam steering with all-metallic epsilon-near-zero lens antenna. Applied Physics Letters, 105(24), doi:10.1063/1.4903865, and may be found at http://dx.doi.org/10.1063/1.4903865. ; An all-metallic steerable beam antenna composed of an ε-near-zero (ENZ) metamaterial lens is experimentally demonstrated at 144 GHz (λ0 = 2.083 mm). The ENZ lens is realized by an array of narrow hollow rectangular waveguides working just near and above the cut-off of the TE10 mode. The lens focal arc on the xz-plane is initially estimated analytically as well as numerically and compared with experimental results demonstrating good agreement. Next, an open-ended waveguide is placed along the lens focal arc to evaluate the ENZ-lens antenna steerability. A gain scan loss below 3 dB is achieved for angles up to plus/minus 15º. ; This work was supported in part by the Spanish Government under Contract Consolider Engineering Metamaterials CSD2008-00066 and Contract TEC2011- 28664-C02-01. V.P.-P. is sponsored by Spanish Ministerio de Educacion, Cultura y Deporte under grant FPU AP-2012- 3796. V.T. is sponsored by the Universidad Publica de Navarra. B.O. is sponsored by Spanish Ministerio de Economıa y Competitividad under Grant FPI BES-2012- 054909. M.B. is sponsored by the Spanish Government via RYC-2011-08221. M.N.-C. is supported by the Imperial College Junior Research Fellowship.

An epsilon-near-zero graded-index converging lens with planar faces is proposed and analyzed. Each perfectly-electric conducting (PEC) waveguide comprising the lens operates slightly above its cut-off frequency and has the same length but different cross-sectional dimensions. This allows controlling individually the propagation constant and the normalized characteristic impedance of each waveguide for the desired phase front at the lens output while Fresnel reflection losses are minimized. A complete theoretical analysis based on the waveguide theory and Fermat's principle is provided. This is complemented with numerical simulation results of two-dimensional and three-dimensional lenses, made of PEC and aluminum, respectively, and working in the terahertz regime, which show good agreement with the analytical work. ; Effort sponsored by Spanish Government under contracts Consolider "Engineering Metamaterials" CSD2008-00066 and TEC2011-28664-C02-01. P.R.-U. is sponsored by the Government of Navarra under funding program "Formación de tecnólogos" 055/01/11. M.N.- C. is supported by the Imperial College Junior Research Fellowship. M. B. acknowledges funding by the Spanish Government under the research contract program Ramon y Cajal RYC-2011-08221. N.E. acknowledges the support from the US Office of Naval Research (ONR) Multidisciplinary University Research Initiatives (MURI) grant number N00014-10-1- 0942.

Trabajo presentado al 2014 Mediterranean Microwave Symposium. Marruecos, 2014. ; Here we perform numerical and experimental investigation of plano-concave all-metallic ε-near-zero (ENZ) lens with operational frequency f = 144 GHz. The ENZ lens is achieved by stacking an array of narrow hollow rectangular waveguides working near cut-off frequency. Focusing and radiation properties are numerically analyzed and measured. The enhancement of 5.61 dB and directivity of 17.6 dBi are shown. Good agreement between experimental and numerical results is demonstrated. ; This work was supported in part by the Spanish Government under contract Consolider Engineering Metamaterials CSD2008-00066 and contract TEC2011-28664-C02-01. B. O. is sponsored by Spanish Ministerio de Economía y Competitividad under grant FPI BES-2012-054909. V.T. is sponsored by the Universidad Pública de Navarra. V.P.-P. is sponsored by Spanish Ministerio de Educación, Cultura y Deporte under grant FPU AP-2012-3796. M.B. is sponsored by the Spanish Government via RYC-2011-08221. M. N.-C. is supported by the Imperial College Junior Research Fellowship.