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Proceedings Paper

High-efficiency wavelength and polarization selective grating-waveguide structures for Yb:YAG thin-disk lasers
Author(s): Martin Rumpel; Marwan Abdou Ahmed; Andreas Voss; Thomas Graf
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Paper Abstract

We report on Grating Waveguide Structures (GWS) with a high diffraction efficiency used in Littrow configuration to select (and tune) the wavelength of an Yb:YAG thin-disk laser. The structures are composed of a multilayer HR coating, on which an additional low index layer (SiO2) and high index layer (Ta2O5) was deposited. A binary grating with a period of 580 nm is etched on top of the structure with a groove depth of 87 nm for GWS 1 and 72 nm for GWS 2. The simulation results show that the diffraction efficiency in the -1st order can reach a value of 99.99% for TE polarization, whereas it is only about 20% for TM polarization at 1030 nm. The grating was fabricated by standard interference lithography followed by a dry etching process to the desired groove depth. The spectroscopic measurement exhibited a diffraction efficiency of 99.6% for GWS 1 at 1030 nm and 99.7% for GWS 2 at 1048 nm. The devices were placed as end-mirror into the resonator of a Yb:YAG thin-disk laser. An output power of up to 110 W could be obtained from the laser in fundamental-mode operation (M2 ≈ 1.2) with GWS 1, corresponding to an optical efficiency of ηoo = 36.2%. In multi-mode operation (M2 ≈ 6) a power of 325 W with ηoo = 53.2% could be extracted. The spectral bandwidth of the emitted beam was measured using an Optical Spectrum Analyzer (OSA) to be less than 20 pm in fundamental-mode. We also showed a continuous wavelength tuning range of 46 nm for GWS 1 and of 38 nm for GWS 2. With a commercially available Stokes polarimeter the degree of linear polarization (DOLP) was measured to be higher than 98.6% over the whole power and wavelength tuning range.

Paper Details

Date Published: 15 May 2012
PDF: 9 pages
Proc. SPIE 8433, Laser Sources and Applications, 84331D (15 May 2012); doi: 10.1117/12.922233
Show Author Affiliations
Martin Rumpel, Univ. Stuttgart (Germany)
Marwan Abdou Ahmed, Univ. Stuttgart (Germany)
Andreas Voss, Univ. Stuttgart (Germany)
Thomas Graf, Univ. Stuttgart (Germany)

Published in SPIE Proceedings Vol. 8433:
Laser Sources and Applications
Thomas Graf; Jacob I. Mackenzie; Helena Jelínková; John Powell, Editor(s)

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