Large optical field enhancement for nanotips with large opening angles

We theoretically investigate the dependence of the enhancement of optical near-fields at nanometric tips on the shape, size, and material of the tip. We confirm the strong dependence of the field enhancement factor on the radius of curvature. In addition, we find a surprisingly strong increase of fi...

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Bibliographic Details
Published inNew journal of physics Vol. 17; no. 6; pp. 63010 - 63026
Main Authors Thomas, Sebastian, Wachter, Georg, Lemell, Christoph, Burgdörfer, Joachim, Hommelhoff, Peter
Format Journal Article
LanguageEnglish
Published Bristol IOP Publishing 10.06.2015
Subjects
Dependence
lightning rod effect
Mathematical analysis
nano-optics
nanotips
Near fields
optical field enhancement
Physics
plasmon resonance
Radius of curvature
Surface charge
Tungsten
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Summary:We theoretically investigate the dependence of the enhancement of optical near-fields at nanometric tips on the shape, size, and material of the tip. We confirm the strong dependence of the field enhancement factor on the radius of curvature. In addition, we find a surprisingly strong increase of field enhancement with increasing opening angle of the nanotips. For gold and tungsten nanotips in the experimentally relevant parameter range (radius of curvature at laser wavelength), we obtain field enhancement factors of up to for Au and for W for large opening angles. We confirm this strong dependence on the opening angle for many other materials featuring a wide variety in their dielectric response. For dielectrics, the opening angle dependence is traced back to the electrostatic force of the induced surface charge at the tip shank. For metals, the plasmonic response strongly increases the field enhancement and shifts the maximum field enhancement to smaller opening angles.
ISSN:1367-2630
1367-2630
DOI:10.1088/1367-2630/17/6/063010