Journal
NANO LETTERS
Volume 16, Issue 7, Pages 4635-4640Publisher
AMER CHEMICAL SOC
DOI: 10.1021/acs.nanolett.6b01958
Keywords
All-dielectric nanodisks; third harmonic generation; anapole mode; electric field enhancement
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Funding
- EPSRC Reactive Plasmonics Programme [EP/M013812/1]
- EPSRC Mathematical Fundamentals of Metamaterials Programme [EP/L024926/1]
- Leverhulme Trust
- ONR Global
- Royal Society
- Lee-Lucas Chair in Physics
- Engineering and Physical Sciences Research Council [EP/P02520X/1, 1413825, EP/M013812/1, EP/L024926/1, EP/I004343/1] Funding Source: researchfish
- EPSRC [EP/I004343/1, EP/L024926/1, EP/M013812/1] Funding Source: UKRI
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We present an all-dielectric germanium nano system exhibiting a strong third order nonlinear response and efficient third harmonic generation in the optical regime. A thin germanium nanodisk shows a pronounced valley in its scattering cross section at the dark anapole mode, while the electric field energy inside the disk is maximized due to high confinement within the dielectric. We investigate the dependence of the third harmonic signal on disk size and pump wavelength to reveal the nature of the anapole mode. Each germanium nanodisk generates a high effective third order susceptibility of chi((3)) = 4.3 x 10(-9) esu, corresponding to an associated third harmonic conversion efficiency of 0.0001% at an excitation wavelength of 1650 nm, which is 4 orders of magnitude greater than the case of an unstructured germanium reference film. Furthermore, the nonlinear conversion via the anapole mode outperforms that via the radiative dipolar resonances by about 1 order of magnitude, which is consistent with our numerical simulations. These findings open new possibilities for the optimization of upconversion processes on the nanoscale through the appropriate engineering of suitable dielectric materials.
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