Efficient subwavelength focusing of light with a long focal depth. Issue 39 (23rd September 2015)

• Record Type: Journal Article
• Authors: Huang, He; Li, Qing; Fu, Jian; Wu, James; Lin, Feng; Wu, Xingkun
• Is Part Of: Nanoscale. Volume 7:Issue 39(2015)
• Page Start: 16504
• Page End: 16507
• Publication Date: 2015-09-23
• Subjects: Nanoscience -- Periodicals; Nanotechnology -- Periodicals; 620.505
• DOI: 10.1039/c5nr04133c
• Languages: English
• ISSNs: 2040-3364

Abstract

Abstract : We demonstrate an efficient method for far-field subwavelength focusing by a novel two-component axicon structure. 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 0.41 λ was achieved at a power efficiency of over 40%, with a focal depth of 9 λ 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.