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Proceedings Paper

High-brightness power delivery for fiber laser pumping: simulation and measurement of low-NA fiber guiding
Author(s): Dan Yanson; Moshe Levy; Ophir Peleg; Noam Rappaport; Moshe Shamay; Nir Dahan; Genady Klumel; Yuri Berk; Ilya Baskin
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Paper Abstract

Fiber laser manufacturers demand high-brightness laser diode pumps delivering optical pump energy in both a compact fiber core and narrow angular content. A pump delivery fiber of a 105 μm core and 0.22 numerical aperture (NA) is typically used, where the fiber NA is under-filled to ease the launch of laser diode emission into the fiber and make the fiber tolerant to bending. At SCD, we have developed multi-emitter fiber-coupled pump modules that deliver 50 W output from a 105 μm, 0.15 NA fiber at 915, 950 and 976 nm wavelengths enabling low-NA power delivery to a customer’s fiber laser network. In this work, we address the challenges of coupling and propagating high optical powers from laser diode sources in weakly guiding step-index multimode fibers. We present simulations of light propagation inside the low-NA multimode fiber for different launch conditions and fiber bend diameters using a ray-racing tool and demonstrate how these affect the injection of light into cladding-bounded modes. The mode filling at launch and source NA directly limit the bend radius at which the fiber can be coiled. Experimentally, we measure the fiber bend loss using our 50 W fiber-coupled module and establish a critical bend diameter in agreement with our simulation results. We also employ thermal imaging to investigate fiber heating caused by macro-bends and angled cleaving. The low mode filling of the 0.15 NA fiber by our brightness-enhanced laser diodes allows it to be coiled with diameters down to 70 mm at full operating power despite the low NA and further eliminates the need for mode-stripping at fiber combiners and splices downstream from our pump modules.

Paper Details

Date Published: 20 February 2015
PDF: 9 pages
Proc. SPIE 9346, Components and Packaging for Laser Systems, 934603 (20 February 2015); doi: 10.1117/12.2079357
Show Author Affiliations
Dan Yanson, SCD SemiConductor Devices (Israel)
Moshe Levy, SCD SemiConductor Devices (Israel)
Ophir Peleg, SCD SemiConductor Devices (Israel)
Noam Rappaport, SCD SemiConductor Devices (Israel)
Moshe Shamay, SCD SemiConductor Devices (Israel)
Nir Dahan, SCD SemiConductor Devices (Israel)
Genady Klumel, SCD SemiConductor Devices (Israel)
Yuri Berk, SCD SemiConductor Devices (Israel)
Ilya Baskin, SCD SemiConductor Devices (Israel)

Published in SPIE Proceedings Vol. 9346:
Components and Packaging for Laser Systems
Alexei L. Glebov; Paul O. Leisher, Editor(s)

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