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High energy amplification of ultrafast pulses in a planar waveguide geometry (Conference Presentation)
Author(s): Kimberly E. Tkalcec; Rolf B. Birch; Howard J. Baker; M. J. Daniel Esser
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Paper Abstract

We present an energy-scalable ultrafast Yb:YAG MOPA system for material processing applications. The system consists of a dual-side-pumped Yb:YAG planar waveguide (PWG) amplification stage that is seeded by a commercial laser, pre-amplified by a dual-end-pumped Yb:YAG single crystal fibre (SCF). The SCF is pumped by two 80 W fibre-coupled laser diodes and amplified the seed (344 fs pulses, 10 MHz, 140 nJ) to 1.4 µJ in a single-pass configuration. Thermal lensing, astigmatism and depolarisation within the SCF was analysed and compensated for by careful selection of beam-shaping optics. The 12 mm wide by 13 mm long PWG crystal has a 150 µm core of 2 at.% Yb:YAG, bonded top and bottom to sapphire cladding of 1 mm thickness. The core is side-pumped using two 540 W phase-corrected diode stacks such that a uniformly distributed high gain was achieved. The advanced crystal design suppresses intra-crystal parasitic oscillations and the PWG geometry significantly alleviates thermal lensing. The seed is multi-passed through the PWG crystal and the mirror parameters were carefully chosen to optimise gain extraction. The seed path is scalable up to 7 passes through the crystal for which 8.7 µJ per pulse was achieved at a pump power of 860 W for sub-ps pulses at 10 MHz. Current investigations include suppression of unwanted parasitic oscillations between the multi-pass mirrors to improve the output beam quality. Future work is aimed at the inclusion of kHz burst modes of sub-ps pulses at 1MHz repetition frequency.

Paper Details

Date Published: 13 March 2019
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Proc. SPIE 10896, Solid State Lasers XXVIII: Technology and Devices, 108960S (13 March 2019); doi: 10.1117/12.2510184
Show Author Affiliations
Kimberly E. Tkalcec, Heriot-Watt Univ. (United Kingdom)
Rolf B. Birch, Heriot-Watt Univ. (United Kingdom)
Howard J. Baker, Heriot-Watt Univ. (United Kingdom)
M. J. Daniel Esser, Heriot-Watt Univ. (United Kingdom)


Published in SPIE Proceedings Vol. 10896:
Solid State Lasers XXVIII: Technology and Devices
W. Andrew Clarkson; Ramesh K. Shori, Editor(s)

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