Tight focusing of laser light using a chromium Fresnel zone plate

V. V. Kotlyar, S. S. Stafeev*, A. G. Nalimov, M. V. Kotlyar, Liam O'Faolain, E. S. Kozlova

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

35 Citations (Scopus)
2 Downloads (Pure)

Abstract

Using near-field scanning microscopy, we demonstrate that a 15-µm zone plate fabricated in a 70-nm chromium film sputtered on a glass substrate and having a focal length and outermost zone's width equal to the incident wavelength λ = 532 nm, focuses a circularly polarized Gaussian beam into a circular subwavelength focal spot whose diameter at the full-width of half-maximum intensity is FWHM = 0.47λ. This value is in near-accurate agreement with the FDTD-aided numerical estimate of FWHM = 0.46λ. When focusing a Gaussian beam linearly polarized along the y-axis, an elliptic subwavelength focal spot is experimentally found to measure FWHMx = 0.42λ (estimated value FWHMx = 0.40λ) and FWHMy = 0.64λ. The subwavelength focal spots presented here are the tightest among all attained so far for homogeneously polarized beams by use of non-immersion amplitude zone plates.

Original languageEnglish
Pages (from-to)19662-19671
Number of pages10
JournalOptics Express
Volume25
Issue number17
Early online date7 Aug 2017
DOIs
Publication statusPublished - 21 Aug 2017

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