Three-Dimensional Resolvable Plasmonic Concentric Compound Lens: Approaching the Axial Resolution from Microscale to Nanoscale

Kai Hao Chang, Yen Chun Chen, Wen-Hao Chang, Po-Tsung Lee*

*Corresponding author for this work

Research output: Contribution to journalArticle

1 Scopus citations

Abstract

We propose the design and working principle of a plasmonic concentric compound lens (CCL) comprising inner circular nanoslits and outer circular nanogrooves. Dual-wavelength operations have been achieved for 650 and 750 nm at nanoscale and microscale focal lengths along with their depth of focus (DOF). By tuning the arrangement of nanogrooves, the axial resolution can be modulated and the narrowest DOF is achieved by a design of gradually decreasing groove width. For the ultrahigh tunability of axial resolution, DOF over 400 nm for both working wavelengths is also achieved. We not only developed an approximate-perturbed-focus model for explaining the performance of DOF but also found an extraordinary way to improve the resolution. The enhanced resonance of central disk as nannoantenna in CCL also has great influence on nanofocusing with different deigns of outer nanogrooves. This work provides new sight of focusing ability governed by the general optical nanogrooves. The optimized CCL shows excellent focusing performance with a lateral resolution down to 0.32λ (λ = 650 nm), which is the best resolving ability achieved thus far in the near field region with a long focal length up to 500 nm.

Original languageEnglish
Pages (from-to)834-843
Number of pages10
JournalACS Photonics
Volume5
Issue number3
DOIs
StatePublished - 21 Mar 2018

Keywords

  • axial resolution
  • depth of focus
  • dual-wavelength
  • Plasmonic lens
  • subwavelength focusing

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