Abstract
The influence of the core diameter and the fiber length on the beam quality of the transmitted beam was investigated theoretically and experimentally for highly multimode step-index fibers with a numerical aperture of 0.22 using a fully monolithic setup. We show that it is possible to maintain a nearly diffraction-limited beam quality ( M $^{2}\boldsymbol{\approx }$ 1.3) through 100 m long multimode fibers. For a core diameter of $60\,\boldsymbol{\mu}$ m and a fiber length of 380 m one can still deliver a beam with an M $^{2}$ value of 2.1. The high-power suitability of this approach was shown by transmitting 1 kW of power through a 100 m long fiber with a core diameter of $60\,\boldsymbol{\mu}$ m without the onset of stimulated Raman scattering while maintaining a nearly diffraction-limited beam quality ( M $^{2} \boldsymbol{\approx }$ 1.3).
Highlights
F OR laser materials processing optical fibers offer a flexible solution for transporting the laser beam from the laser source to the work piece
The splice parameters after each run of experiments were adapted until the best parameters were found to minimize power loss, light propagating in the fiber cladding, and the beam quality factor M 2 of the transmitted beam
The beam transmitted through the fiber was analyzed with respect to power, beam quality, and the optical spectrum
Summary
F OR laser materials processing optical fibers offer a flexible solution for transporting the laser beam from the laser source to the work piece. The fiber delivery of high-brightness solid-state laser radiation is limited by to the onset of nonlinear effects. The output of industrial high-power cw fiber lasers typically exhibits a broad spectral bandwidth [1], the dominant nonlinearity in the delivery fibers is stimulated Raman scattering (SRS) [2]. To overcome SRS and enable the fiber-optic transmission of high-power laser beams over long distances the core size must be enlarged, making the fiber multimode. Manuscript received January 22, 2019; revised May 16, 2019; accepted June 4, 2019. Date of publication June 13, 2019; date of current version August 16, 2019.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
