Issue 39, 2015
From the journal:

Nanoscale

Efficient subwavelength focusing of light with a long focal depth

He Huang,a   Qing Li,a   Jian Fu,a   James Wu,b   Feng Linc  and  Xingkun Wu*a  

* Corresponding authors

a College of Optical Science and Engineering, Zhejiang University, Hangzhou, China
E-mail: xingkunwu@zju.edu.cn

b Department of Bioengineering, University of Washington, Seattle, WA 98195, USA

c College of Engineering, Nanyang Technological University, Singapore

Abstract

We demonstrate an efficient method for far-field subwavelength focusing by a novel two-component axicon structure. Annular beams generated by a fiber axicon are focused using a micro-cone reflector, creating a quasi-Bessel beam with a high convergence angle of up to 40°. A center focal spot diameter of 0.41λ was achieved at a power efficiency of over 40%, with a focal depth of 9λ and a working distance as long as 35 μm. We further demonstrate that experimental knife-edge measurements mapping the beam focal intensity agree with numerical simulations of the structure. This method shows demonstrable promise in overcoming the optical focusing limit of single-element axicons and great potential for use in high tolerance, high-resolution applications in optical systems.

Graphical abstract: Efficient subwavelength focusing of light with a long focal depth

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Article information

DOI
https://doi.org/10.1039/C5NR04133C
Article type
Paper
Submitted
22 Jun 2015
Accepted
03 Sep 2015
First published
09 Sep 2015

Nanoscale, 2015,7, 16504-16507

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Efficient subwavelength focusing of light with a long focal depth

H. Huang, Q. Li, J. Fu, J. Wu, F. Lin and X. Wu, Nanoscale, 2015, 7, 16504 DOI: 10.1039/C5NR04133C

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