3D laser nano-printing on fibre paves the way for super-focusing of multimode laser radiation


Multimode high-power laser diodes suffer from inefficient beam focusing, leading to a focal spot 10–100 times greater than the diffraction limit. This inevitably restricts their wider use in ‘direct-diode’ applications in materials processing and biomedical photonics. We report here a ‘super-focusing’ characteristic for laser diodes, where the exploitation of self-interference of modes enables a significant reduction of the focal spot size. This is achieved by employing a conical microlens fabricated on the tip of a multimode optical fibre using 3D laser nano-printing (also known as multi-photon lithography). When refracted by the conical surface, the modes of the fibre-coupled laser beam self-interfere and form an elongated narrow focus, usually referred to as a ‘needle’ beam. The multiphoton lithography technique allows the realisation of almost any optical element on a fibre tip, thus providing the most suitable interface for free-space applications of multimode fibre-delivered laser beams. In addition, we demonstrate the optical trapping of microscopic objects with a super-focused multimode laser diode beam thus rising new opportunities within the applications sector where lab-on-chip configurations can be exploited. Most importantly, the demonstrated super-focusing approach opens up new avenues for the ‘direct-diode’ applications in material processing and 3D printing, where both high power and tight focusing is required.

Publication DOI: https://doi.org/10.1038/s41598-018-32970-6
Divisions: Engineering & Applied Sciences > Aston Institute of Photonics Technology
Additional Information: This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. Te images or other third party material in this article are included in the article’s Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/. © The Author(s) 2018
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Related URLs: http://www.natu ... 598-018-32970-6 (Publisher URL)
PURE Output Type: Article
Published Date: 2018-10-02
Accepted Date: 2018-09-17
Authors: Sokolovskii, Grigorii S.
Melissinaki, Vasileia
Fedorova, Ksenia A. (ORCID Profile 0000-0002-2765-9951)
Dudelev, Vladislav V.
Losev, Sergey N.
Bougrov, Vladislav E.
Sibbett, Wilson
Farsari, Maria
Rafailov, Edik U. (ORCID Profile 0000-0002-4152-0120)



Version: Published Version

License: Creative Commons Attribution

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