Reflectionless Sharp Bends and Corners in Waveguides Using Epsilon-Near-Zero Effects

Following our recent theoretical and experimental results that show how zero-permittivity metamaterials may provide anomalous tunneling and energy squeezing through ultranarrow waveguide channels, here we report an experimental investigation of the bending features relative to this counterintuitive resonant effect. We generate the required effectively-zero permittivity using a waveguide operating at the cut-off of its dominant mode, and we show how sharp and narrow bends may be inserted within the propagation channel without causing any sensible reflection or loss.Comment: 13 pages, 6 figure

Optical emission near a high-impedance mirror

Solid state light emitters rely on metallic contacts with high sheet-conductivity for effective charge injection. Unfortunately, such contacts also support surface plasmon polariton (SPP) excitations that dissipate optical energy into the metal and limit the external quantum efficiency. Here, inspired by the concept of radio-frequency (RF) high-impedance surfaces and their use in conformal antennas we illustrate how electrodes can be nanopatterned to simultaneously provide a high DC electrical conductivity and high-impedance at optical frequencies. Such electrodes do not support SPPs across the visible spectrum and greatly suppress dissipative losses while facilitating a desirable Lambertian emission profile. We verify this concept by studying the emission enhancement and photoluminescence lifetime for a dye emitter layer deposited on the electrodes

Sampling and Squeezing Electromagnetic Waves through Subwavelength Ultranarrow Regions or Openings

Here, we investigate the physical mechanisms that may enable squeezing a complex electromagnetic field distribution through a narrow and/or partially obstructed region with little amplitude and phase distortions. Following our recent works, such field manipulations may be made possible by a procedure in which the incoming wave is first “sampled” “pixel by pixel” using an array of metallic waveguides, and in a second step the energy corresponding to each individual pixel is “squeezed” through a very narrow channel filled with a permittivity-near-zero material. In this work, we study in detail these processes in scenarios in which the electromagnetic wave is compressed along a single direction of space and present theoretical models that enable the analytical modeling of such phenomena. Full-wave results obtained with an electromagnetic simulator, demonstrate the possibility of compressing an incoming wave several folds through ultranarrow channels filled with silicon carbide. The “sampling and squeezing” concept may enable unparalleled control of electromagnetic waves in the nanoscale

Transformation Electronics: Tailoring the Effective Mass of Electrons

The speed of integrated circuits is ultimately limited by the mobility of electrons or holes, which depend on the effective mass in a semiconductor. Here, building on an analogy with electromagnetic metamaterials and transformation optics, we describe a transport regime in a semiconductor superlattice characterized by extreme anisotropy of the effective mass and a low intrinsic resistance to movement—with zero effective mass—along some preferred direction of electron motion. We theoretically demonstrate that such a regime may permit an ultrafast, extremely strong electron response, and significantly high conductivity, which, notably, may be weakly dependent on the temperature at low temperatures. These ideas may pave the way for faster electronic devices and detectors and functional materials with a strong electrical response in the infrared regime

Transporting an Image through a Subwavelength Hole

The manipulation of optical waves in the subwavelength scale is limited by diffraction. In the vicinity of a narrow aperture, the amplitude of the electric field is approximately uniform and the transmissivity is extremely low. Here we show that despite these fundamental constraints it may be possible to transport and redirect a complex electromagnetic image through a tiny subwavelength hole with diameter considerably smaller than the diameter of the image, without losing the subwavelength details. The proposed concepts hold promise for an unprecedented manipulation of the electromagnetic and optical fields in the nanoscale with potential applications in imaging and sensing