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.

Optical Antenna Properties of Scanning Probe Tips: Plasmonic Light Scattering, Tip−Sample Coupling, and Near-Field Enhancement

Abstract: The optical near-field distribution and enhancement near the apex of model scanning probe tips are calculated within the quasistatic approximation. The optical tip−sample coupling sensitively depends on both the tip and sample material. This, in addition to the tip−sample distance and apex geometry, is found to affect the spatial resolution that can be obtained in scattering near-field microscopy (s-SNOM). A pronounced structural plasmon resonant behavior is found for gold tips, which redshifts upon tip−sample approach on the length scale given by the tip radius. This near-field tip−sample coupling also allows for surface plasmon excitation in the sample. With the critical dimensions of the tip apex in the range of 10 to several 10s of nanometers, the results are found to be in good agreement with experiment and more rigorous theoretical treatments.

Laser-Generated Cavitation in Absorbing Liquid Induced by Acoustic Diffraction

Abstract: Conversion of energy from a heat pulse to acoustic stress is theoretically and experimentally studied in detail. The heat pulse was generated by laser radiation delivered via an optical fiber into an absorbing liquid. The experimental results indicate that tensile stress and cavitation are induced in front of the fiber tip at a distance far below the optical penetration depth of the laser radiation. The occurrence of tensile stress in the acoustic near field of a submerged fiber is explained by acoustic diffraction of the thermoelastic expansion wave. Good agreement between experimental results and theoretical calculations based on a three-dimensional model was found.

SPASYN-an electromagnetic relative position and orientation tracking system

Abstract: Two relatively remote independent body coordinate frames are related in both position and orientation (six degrees of freedom) using precise electromagnetic field measurements. Antenna triads are fixed in each body frame. Variously polarized excitations in one body are correlated with signals detected in the remote body. Near-field and far-field processing strategies are presented with applications.

Near-field manipulation of spectroscopic selection rules on the nanoscale

Abstract: In conventional spectroscopy, transitions between electronic levels are governed by the electric dipole selection rule because electric quadrupole, magnetic dipole, and coupled electric dipole-magnetic dipole transitions are forbidden in a far field. We demonstrated that by using nanostructured electromagnetic fields, the selection rules of absorption spectroscopy could be fundamentally manipulated. We also show that forbidden transitions between discrete quantum levels in a semiconductor nanorod structure are allowed within the near-field of a noble metal nanoparticle. Atomistic simulations analyzed by an effective mass model reveal the breakdown of the dipolar selection rules where quadrupole and octupole transitions are allowed. Our demonstration could be generalized to the use of nanostructured near-fields for enhancing light-matter interactions that are typically weak or forbidden.