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Journal of Directed Energy
Volume 4, Number 1
The papers listed below constitute Volume 4, Number 1 of the Journal of Directed Energy.
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The History of Thin-Disk Laser Development
Adolf Giesen, German Aerospace Center, Institute of Technical Physics
This paper describes thin-disk laser history starting with the industrial laser environment in Germany in the
1970s. The background of the invention is discussed along with the German political and research
environment. Thin-disk laser design and performance are then discussed in detail. Results for
continuous-wave and pulsed operation as well as for amplification of short (nanosecond) and ultra-short
(picosecond, femtosecond) pulses demonstrate the potential of thin-disk laser design. Advantages for
using various laser materials are explained, as well as applicability of the thin-disk laser concept
to optically pumped semiconductor structures. Finally, an overview is presented of German research and
development practices and of patenting and licensing policies. The last section describes industrial
applications of thin-disk laser technology.
KEYWORDS: Solid-state laser, Thin disk laser
Thermal Modeling of the Thin Disk Laser
Jochen Speiser, German Aerospace Center, Institute of Technical Physics
This paper discusses the needs and requirements of modeling the thin disk laser with a focus on thermal
modeling. Results concerning high power extraction (>10 kW with one disk), including thermal behavior,
stress, and thermal lenses are presented. Challenges of modeling high energy storage in a thin disk
amplifier are discussed. An approachfor modeling the influence of amplified spontaneous emission on the
transient behavior of the inversion is described. In addition, an approach to find scaling limits due
to amplified spontaneous emission is briefly described and results are presented.
KEYWORDS: Solid-state laser, Thin disk laser, Numerical modeling, Scaling limit
Fabrication and Processing Technologies for Thin-Disk Laser Elements
Nicholas G. Traggis, Neil R. Claussen, Christopher S. Wood, and Ove Lyngnes, Precision Photonics Corporation
With the continued advancement of high power, solid-state laser technology, a thorough understanding of
optical fabrication techniques and how they impact spectral performance, thermal management, and damage
threshold is required. Given their very unique form factor, thin disk lasers offer particular challenges
in fabrication. This paper presents a review of fabrication technologies for thin-disk laser elements.
In particular, we review current technologies for polishing, assembly, thin film coating, mounting, and
KEYWORDS: Epoxy-free, Adhesive-free YAG, Ion beam sputtering, Laser damage threshold, Soldering, Thin disk, Solid-state laser
Characterization of a Multikilowatt, Yb:YAG, Ceramic Thin-Disk Laser
Ahmed Lobad and Don Stalnaker, Boeing LTS Inc.; L.A. (Vern) Schlie, Integral Laser Solutions; and T. Sean Ross and William P. Latham, AFRL/RD, Directed Energy Directorate
The operation of a 1030-nm, single thin-disk laser, which produced 6.5 kW of laser output power with 57% slope
efficiency is reported. The Yb: YAG ceramic gain element is 200 Ám thick, and bonded to a l-mm thick,
undoped ceramic YAG cap. The gain element is pumped by diode lasers at 940 nm. The maximum incident pump
intensity was 5.2 kW/cm2, yielding an output intensity of 2.6 kW/cm2 of multi mode laser radiation.
Rigrod analysis suggested that the laser operates with inhomogeneous gain saturation. Enhanced spatial
hole burning in the active-mirror gain element is responsible for this effective inhomogeneous
saturation. Full modulation of the intracavity intensity within the gain at the high reflector leads to
poor gain extraction close to the intensity null regions and reduced effective gain length. The
independence of the pump threshold and output intensities on the pump spot size indicates that the axial
gain is not clamped by the transverse amplified spontaneous emission for up to a pump spot diameter of
18 mm. Observed thermal lensing contributions include thermal expansion-induced disk flexure, pump
edge-induced temperature profile, and strong thermal imprint of the cooling nozzle due to the direct jet
impingement on the high-reflection coated side. Weak absorption of the 1030-nm intracavity intensity in
the undoped cap led to excess heating that limited the extracted intensity.
KEYWORDS: High-power lasers, Yb:YAG, Thin disk laser
Development of High-Brightness Thin Disk Lasers
Alan Ullman, Mark Curtin, Gregory Needham, Harry Wang, and Louis Zeldin, The Boeing Company, Directed Energy Systems
Testing of a multidisk thin-disk laser has been conducted using a unique multipass resonator that provides
aberration and mode controlas well as high gain. The disk modules used were derived from commercial thin
disk lasers. The laser consistently produced a power level of 28 kW, beam quality of 2.7, and an
optical-to-optical efficiency of 43%. No adaptive optics are required to achieve these results. Based on
these results, a modified resonator should achieve single-mode operation with optical-to-optical
efficiency of 55% and beam quality of less than 2.0 without adaptive optics. Disk scaling studies have
shown that amplified spontaneous emission can be controlled to a disk size consistent with 100 kW or
greater power levels.
KEYWORDS: High brightness laser, High power lasers, Mode control, Thin disk laser, Unstable resonator
Volume 4, Number 1, Journal of Directed Energy
Last updated: 6 September 2017