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Proceedings Paper

Simultaneous frequency stabilization and high-power dense wavelength division multiplexing (HP-DWDM) using an external cavity based on volume Bragg gratings (VBGs)
Author(s): Stefan Hengesbach; Sarah Klein; Carlo Holly; Ulrich Witte; Martin Traub; Dieter Hoffmann
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Paper Abstract

Multiplexing technologies enable the development of high-brightness diode lasers for direct industrial applications. We present a High-Power Dense Wavelength Division Multiplexer (HP-DWDM) with an average channel spacing of 1.7 (1.5) nm and a subsequent external cavity mirror to provide feedback for frequency stabilization and multiplexing in one step. The "self-optimizing" multiplexing unit consists of four reflective Volume Bragg Gratings (VBGs) with 99% diffraction efficiency and seven dielectric mirrors to overlay the radiation of five input channels with an adjustable channel spacing of 1-2 nm. In detail, we focus on the analysis of the overall optical efficiency, the change of the beam parameter product and the spectral width. The performance is demonstrated using five 90 μm multimode 9xx single emitters with M2≤17. Because of the feedback the lateral (multimodal) spatial and angular intensity distribution changes strongly and the beam parameter product decreases by a factor of 1.2 to 1.9. Thereby the angular intensity distribution is more affected than the width of the beam waist. The spectral width per emitter decreases to 3-200 pm (FWHM) depending on the injection current and the reflectance of the feedback mirror (0.75%, 1.5%, 4%, 6% or 8%). The overall optical multiplexing efficiency ranges between 77% and 86%. With some modifications (e.g. enhanced AR-coatings) we expect 90-95%.

Paper Details

Date Published: 4 March 2016
PDF: 15 pages
Proc. SPIE 9733, High-Power Diode Laser Technology and Applications XIV, 97330K (4 March 2016); doi: 10.1117/12.2212550
Show Author Affiliations
Stefan Hengesbach, Fraunhofer-Institut für Lasertechnik (Germany)
Sarah Klein, RWTH Aachen Univ. (Germany)
Carlo Holly, Fraunhofer-Institut für Lasertechnik (Germany)
Ulrich Witte, Fraunhofer-Institut für Lasertechnik (Germany)
Martin Traub, Fraunhofer-Institut für Lasertechnik (Germany)
Dieter Hoffmann, Fraunhofer-Institut für Lasertechnik (Germany)


Published in SPIE Proceedings Vol. 9733:
High-Power Diode Laser Technology and Applications XIV
Mark S. Zediker, Editor(s)

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