Near-field Localization in Plasmonic Superfocusing: a Nanoemitter on a Tip
The effective focusing of light to sub-wavelength dimensions has been a long standing desire in optics, yet proven challenging even resorting to a multitude of new strategies based on near-field effects, surface plasmon polaritons, and metamaterials1-7. The propagation of surface plasmon polaritons (SPP) on a conical tip to obtain nanoconfined light as proposed theoretically has recently emerged as a particularly promising candidate5-10. On the basis of our previous work, having established coupling of SPPs onto gold metal tips and their radiationless transport11, here, using a refined geometry we provide direct evidence of plasmonic nanofocusing into a localized excitation at the apex. As demonstrated by employing scattering-type scanning near-field optical microscopy (s-SNOM) efficient convergence of the optical fields into the 20 nm size apex volume is shown, exceeding the diffraction limit by more than one order of magnitude. The resulting nanoemitter is a point-like axial dipole with corresponding spectral and angular radiative characteristics. The associated linear and nonlinear field concentration as enabled by the unique 3D topology of the conical tip opens up exciting new applications in nano-optics, facilitating ultra-high spatio-temporal optical imaging, attosecond XUV generation, or antenna-based sensing and energy harvesting.
- Research Organization:
- Pacific Northwest National Lab. (PNNL), Richland, WA (United States). Environmental Molecular Sciences Lab. (EMSL)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- AC05-76RL01830
- OSTI ID:
- 972523
- Report Number(s):
- PNNL-SA-65996; 26701; KP1704020; TRN: US1001603
- Journal Information:
- Nano Letters, 10(2):592–596, Vol. 10, Issue 2
- Country of Publication:
- United States
- Language:
- English
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