Near and far field

About: Near and far field is a research topic. Over the lifetime, 15922 publications have been published within this topic receiving 220571 citations.

A Robust UHF Near-Field RFID Reader Antenna

Abstract: A novel broadband antenna for ultrahigh-frequency (UHF) near-field radio frequency identification (RFID) applications is presented. The antenna is composed of a grounded coplanar waveguide (GCPW), a coplanar stripline (CPS), a lumped balun, multiple resistors, and a finite-sized ground plane. The load impedance is equal to the characteristic impedance of the CPS, hence traveling wave can transmit along the CPS. The proposed antenna structure can produce large currents along the CPS so that a strong and uniform magnetic field distribution is excited in the adjacent region around the antenna. The antenna geometry, design concept, simulated, and measured results are carefully discussed throughout the paper. Measurements show that the antenna operating with a commercial reader demonstrates good performance of tag identification with inductive coupling for near-field RFID applications. In addition, the parametric study is conducted to facilitate the design and optimization processes for engineers.

Reversible polarization control of single photon emission

Abstract: We present reversible and a-priori control of the polarization of a photon emitted by a single molecule by introducing a nanoscale metal object in its near field. It is experimentally shown that, with the metal close to the emitter, the polarization ratio of the emission can be varied by a factor of 2. The tunability of polarization decays, when the metal is displaced by typically 30 nm. Calculations based on the multiple multipole method agree well with our experiments and predict even further enhancement with a suitable nanoantenna design.

Superoscillatory diffraction-free beams

Abstract: It is theoretically shown that by superimposing diffraction-free solutions of the Helmholtz equation, one can construct localized diffraction-free beams that pass through predetermined points on subwavelength distances. These beams are based on the phenomenon of superoscillations and thus do not contain any evanescent waves. The effect of an aperture and noise is examined in specific examples where truncated beams with λ/3 subwavelength features can propagate into the far field.

Imaging profiles of light intensity in the near field: applications to phase-shift photolithography.

Abstract: We describe a method of imaging the intensity profiles of light in near-field lithographic experiments directly by using a sensitive photoresist. This technique was applied to a detailed study of the irradiance distribution in the optical near field with contact-mode photolithography carried out by use of elastomeric phase masks. The experimental patterns in the photoresist determined by scanning electron microscopy and atomic force microscopy were compared with the corresponding theoretical profiles of intensity calculated by use of a simple scalar analysis; the two correlate well. This comparison makes it possible to improve the theoretical models of irradiance distribution in the near field. Analysis of the images highlights issues in the experimental design, provides a means for the optimization of this technique, and extends its application to the successful fabrication of test structures with linewidths of ∼50 nm.