Disk laser

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Structure of a disk laser, 1993. Shown in dark: pump radiation from a laser diode. Bright: laser radiation from the disk laser.

A disk laser (engl .: disk laser ) is one form of the solid state laser wherein the active medium (laser crystal) has the shape of a disc (engl .: disc) has. The energy necessary for the generation of the laser radiation is generated by multiple passage of pump radiation through the laser disk (thickness usually between 80 µm and 200 µm). This disk has a highly reflective coating on its back and also serves as a resonator mirror .

The advantage of the disk geometry of the laser medium is the better cooling of the laser crystal: This is attached to a heat sink with the mirrored surface. Due to the small thickness of the disk, compared to its diameter of sometimes more than one centimeter, the heat is dissipated almost exclusively via the base of the disk. Thus, a temperature gradient can be found almost exclusively perpendicular to the pane surface, but not within the pane plane. This leads to a reduction in the mechanical stresses that arise during operation due to thermal expansion of the pane, which in many other high-power solid-state lasers has a negative effect on the beam quality (focusability).

In contrast to the example figure on the right, the crystal material used in commercial applications so far is ytterbium-doped yttrium-aluminum-garnet (Yb: YAG) with an emission wavelength of 1030 nm. In this case, the optical pumping is carried out with InGaAs laser diodes at a wavelength of 940 nm. The efficiency of a Yb: YAG disk laser is up to 70% based on the irradiated pump power.

The disk laser was developed by Adolf Giesen at the Institute for Beam Tools ( University of Stuttgart ) and made ready for use (primarily cutting and welding metals) at Haas (now part of Trumpf ). The Trumpf company now offers disk lasers which, with a power of up to 16 kW, achieve an electrical efficiency of approx. 25% (50% electrical-optical efficiency of the diode laser and 50% optical-optical efficiency of the disk). The beam parameter product in this case is approx. 8 mm mrad.

Compare also optically pumped semiconductor lasers (also called semiconductor disk lasers).

literature

  • Christian Stolzenburg: Highly repetitive short-pulse disk lasers in the infrared and green spectral range . Herbert Utz Verlag, Munich 2011, ISBN 978-3-8316-4041-6

Individual evidence

  1. K. Ueda, N. Uehara: Laser-diode-pumped solid state lasers for gravitational wave antenna . In: Proceedings of SPIE . 1837, 1993, pp. 336-345. doi : 10.1117 / 12.143686 .
  2. ^ A. Giesen, H. Huegel, A. Voss, K. Wittig, U. Brauch, H. Opower: Scalable concept for diode-pumped high-power solid-state lasers . In: Applied Physics B . 58, No. 5, 1994, pp. 365-372.