Ultrafast Laser Physics

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SESAM damage

SESAM damage is not an issue or a limitation if the SESAM is designed and grown correctly. Why? See below.

SESAMs for ultrafast thin disk lasers operate at multi-kW intracavity powers and tens of µJ intracavity pulse energies and therefore require large saturation fluences, low non-saturable losses, and high damage thresholds.
We present in the paper below the first detailed study on SESAMs for high power oscillators, identifying damage mechanisms and developing optimized design guidelines. We characterize nonlinear reflectivity and damage at unprecedentedly high fluences with a modelocked 1030-nm high energy thin-disk laser. We compare 15 quantum-well (QW) SESAMs with different absorber sections and top-coatings.

Surprisingly, our data shows that catastrophic damage at high fluences does not seem to be related to the specific design of the absorber section (such as strain, number of QW layers, thickness, or indium content). Instead, damage seems to occur due to heating of the lattice by Inverse Saturable Absorption (ISA).

We clearly can demonstrate that the damage fluence Fd scales proportionally to the absorbed energy by ISA for all tested SESAMs. Furthermore, we present guidelines on how to design samples with high saturation fluences, reduced ISA and high damage thresholds. Using multiple QWs and a suitable dielectric topsection, we achieved SESAMs with saturation fluences > 200 μJ/cm2, nonsaturable losses < 0.1% and reduced ISA. Our best sample could not be damaged at the maximum available fluence of 0.21 J/cm2, corresponding to a peak intensity of 370 GW/cm2.

Ref. [323] C. J. Saraceno, C. Schriber, M. Mangold, M. Hoffmann, O. H. Heckl, C. R. E. Baer, M. Golling, T. Südmeyer, U. Keller
“SESAMs for high-power oscillators: design guidelines and damage thresholds” – Invited Paper
IEEE J. Selected Topics in Quantum Electronics (JSTQE), vol. 18, No. 1, pp. 29-41, 2012 (published online 13. Jan. 2011) DownloadDownload (PDF, 1.1 MB)

Additional improvements for SESAM mode locking:

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