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. 2017 Jun 30;7:4485. doi: 10.1038/s41598-017-04490-2

Figure 1.

Figure 1

(a) optical fibre probe design composed by the SM fibre and the MM segment; (b) Fresnel phase/zone plate characteristic ring structure; (c) Fresnel zone plate on the tip of the optical fibre (coated with 20 nm Pt film); (d) Fresnel phase plate on the tip of the optical fibre (no film).