Planar chiral optical metamaterials

Papakostas, Aris (2007) Planar chiral optical metamaterials. University of Southampton, Doctoral Thesis.

Abstract

Planar chiral metamaterials have been manufactured by patterning metallic and dielectric materials on silicon substrates. The metallic samples consisted of a tri-layer of Ti/Au/Ti (20nm/100nm/20nm) on double polished silicon wafers, onto which a patterns of chiral arrays has been transferred using electron beam lithography and ion beam milling, Similar, dielectric samples have beam fabricated using a thin layer (300nm) of UVIII photoresist.

We have investigated the polarization properties of first-order diffracted beams of these planar chiral metamaterials and examined any special optical manifestation of planar chirality for structures of different geometrical chirality using the “rotating waveplate” polarimetric technique. We have observed polarization azimuth rotation and changes in ellipticity in the first-order diffracted beams. At some particular angels of glazing incidence we have observed conversions of linearly polarized light to perfectly circular and vice versa.

Polarization changes of about 10^o for azimuth rotation and ellipticity have been observed, for the first order diffracted beams at normal incidence in reflection, while changes of 15^o have been observed in transmission at 1520nm wavelengths, for metallic structures. At glazing incidence the polarization changes increased up to 30^o. Finally we have investigated whether two-dimensional chiral structures have the same symmetrical properties as the three-dimensional chirality and in this work we have investigated the non-reciprocity properties.

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