scholarly journals Numerical Investigation of the System-Matrix Method for Higher-Order Probe Correction in Spherical Near-Field Antenna Measurements

2012 ◽  
Vol 2012 ◽  
pp. 1-8 ◽  
Author(s):  
Thorkild B. Hansen
Keyword(s):  
Condition Number ◽  
Matrix Method ◽  
Near Field ◽  
Higher Order ◽  
Normal Matrix ◽  
Identity Matrix ◽  
System Matrix ◽  
Higher Order Modes ◽  
Near Field Scanning ◽  
Least Squares Approach

The system-matrix method for higher-order probe correction in spherical near-field scanning is based on a renormalized least-squares approach in which the normal matrix closely resembles the identity matrix when most of the energy of the probe pattern resides in the first-order modes. This method will be “stressed-tested” in the present paper by employing probes for which up to 49% of the pattern energy resides in the higher-order modes. The condition number of the resulting normal matrix will be computed, and its “distance” from the identity matrix displayed. It is also shown how the condition number of the normal matrix can be further reduced.

scholarly journals Dye-doped spheres with plasmonic semi-shells: Lasing modes and scattering at realistic gain levels

2013 ◽  
Vol 4 ◽  
pp. 974-987 ◽  
Author(s):  
Nikita Arnold ◽  
Boyang Ding ◽  
Calin Hrelescu ◽  
Thomas A Klar
Keyword(s):  
Cross Section ◽  
Near Field ◽  
Field Enhancement ◽  
Higher Order ◽  
Silver Layer ◽  
Far Field ◽  
Spectral Features ◽  
Polystyrene Spheres ◽  
Higher Order Modes ◽  
Lasing Modes

We numerically simulate the compensation of absorption, the near-field enhancement as well as the differential far-field scattering cross section for dye-doped polystyrene spheres (radius 195 nm), which are half-covered by a silver layer of 10–40 nm thickness. Such silver capped spheres are interesting candidates for nanoplasmonic lasers, so-called spasers. We find that spasing requires gain levels less than 3.7 times higher than those in commercially available dye-doped spheres. However, commercially available concentrations are already apt to achieve negative absorption, and to narrow and enhance scattering by higher order modes. Narrowing of the plasmonic modes by gain also makes visible higher order modes, which are normally obscured by the broad spectral features of the lower order modes. We further show that the angular distribution of the far-field scattering of the spasing modes is by no means dipole-like and is very sensitive to the geometry of the structure.

scholarly journals k-space imaging of the eigenmodes of sharp gold tapers for scanning near-field optical microscopy

2013 ◽  
Vol 4 ◽  
pp. 603-610 ◽  
Author(s):  
Martin Esmann ◽  
Simon F Becker ◽  
Bernard B da Cunha ◽  
Jens H Brauer ◽  
Ralf Vogelgesang ◽  
...  
Keyword(s):  
Spatial Frequency ◽  
Optical Microscopy ◽  
Frequency Domain ◽  
Near Field ◽  
Higher Order ◽  
Far Field ◽  
Radiation Patterns ◽  
Background Ratio ◽  
Higher Order Modes ◽  
Spatial Frequency Domain

We investigate the radiation patterns of sharp conical gold tapers, which were designed as adiabatic nanofocusing probes for scanning near-field optical microscopy (SNOM). Field calculations show that only the lowest order eigenmode of such a taper can reach the very apex and thus induce the generation of strongly enhanced near-field signals. Higher-order modes are coupled into the far field at finite distances from the apex. Here, we demonstrate experimentally how to distinguish and separate between the lowest and higher-order eigenmodes of such a metallic taper by filtering in the spatial frequency domain. Our approach has the potential to considerably improve the signal-to-background ratio in spectroscopic experiments at the nanoscale.

Study of TiN nanodisks with regard to application for Heat-Assisted Magnetic Recording

MRS Advances ◽  
2016 ◽  
Vol 1 (5) ◽  
pp. 317-326 ◽  
Author(s):  
Jacek Gosciniak ◽  
John Justice ◽  
Umar Khan ◽  
Brian Corbett
Keyword(s):  
Titanium Nitride ◽  
Data Storage ◽  
Near Field ◽  
Polarized Light ◽  
Higher Order ◽  
Plasmonic Material ◽  
Order Resonance ◽  
Resonance Modes ◽  
Higher Order Modes ◽  
Transmission Measurements

ABSTRACTIn recent years titanium nitride is being considered as a very promising plasmonic material for data storage applications as it exhibits a pronounced plasmonic dipolar resonance and has high thermal stability. However, there is a lack of research where higher order resonance modes are examined. We address this here by performing angle dependent spectral transmission measurements nanodisks arrays made from titanium nitride. The measurements show strong polarization dependence with s-polarized light causing excitation of the quadrupole and higher order resonance plasmonic modes. These higher order modes are required for the state-of-the-art designs of near-field transducers. This, together with its outstanding thermal properties, makes TiN a favourable material for data storage applications.

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