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Magnetic probe for material characterization at optical frequencies

Tomasz Antosiewicz (Institutionen för teknisk fysik, Kondenserade materiens teori) ; P. Wróbel ; T. Szoplik
Proceedings of SPIE - The International Society for Optical Engineering. Metamaterials VI, Prague, 20-21 April 2011 (0277-786X). Vol. 8070 (2011),
[Konferensbidrag, refereegranskat]

Rapid development of novel, functional metamaterials made of purely dielectric, plasmonic, or composite structures which exhibit tunable optical frequency magnetic responses creates a need for new measurement techniques. We propose a method of actively measuring magnetic responses, i.e. magnetic dispersion, of such metamaterials within a wide range of optical frequencies with a single probe by exciting individual elementary cells within a larger matrix. The probe is made of a tapered optical fiber with a radially corrugated metal coating. It concentrates azimuthally polarized light in the near-field below the apex into a subwavelength size focus of the longitudinal magnetic field component. An incident azimuthally polarized beam propagates in the core until it reaches the metal stripes of constant angular width running parallel to the axis. For a broad frequency range light-to-plasmon coupling is assured as the lattice constant changes with the radius due to constant angular width. Bound plasmonic modes in slits between the metal stripes propagate toward the apex where circular currents in stripes and displacement currents in slits generate a strong longitudinal magnetic field. The energy density of the longitudinal magnetic component in the vicinity of the axis is much stronger than that of all the other components combined, what allows for pure magnetic excitation of magnetic resonances rather than by the electric field. The scattered signal is then measured in the far-field and analyzed.

Nyckelord: Integrated optics devices, Magnetooptical materials, Metamaterials, Scanning microscopy, Surface plasmons



Denna post skapades 2011-09-13. Senast ändrad 2014-03-19.
CPL Pubid: 146132

 

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Institutioner (Chalmers)

Institutionen för teknisk fysik, Kondenserade materiens teori (1900-2015)

Ämnesområden

Teknisk fysik

Chalmers infrastruktur