High Power Laser Science and Engineering, (2014), Vol. 2, e20, 7 pages.
© Author(s) 2014. The online version of this article is published within an Open Access environment subject to the conditions of the
Creative Commons Attribution licence <http://creativecommons.org/licences/by/3.0>.
doi:10.1017/hpl.2014.26
The all-diode-pumped laser system POLARIS – an
experimentalist’s tool generating ultra-high contrast
pulses with high energy
Marco Hornung
1,2
, Hartmut Liebetrau
2
, Andreas Seidel
2
, Sebastian Keppler
2
, Alexander Kessler
1
,
J
¨
org
K
¨
orner
2
, Marco Hellwing
2
, Frank Schorcht
1
, Diethard Kl
¨
opfel
2
, Ajay K. Arunachalam
1
, Georg A.
Becker
2
, Alexander S
¨
avert
1,2
, Jens Polz
2
, Joachim Hein
1,2
, and Malte C. Kaluza
1,2
1
Helmholtz-Institute Jena, Germany
2
Institute of Optics and Quantum Electronics, Jena, Germany
(Received 28 February 2014; revised 25 April 2014; accepted 6 June 2014)
Abstract
The development, the underlying technology and the current status of the fully diode-pumped solid-state laser system
POLARIS is reviewed. Currently, the POLARIS system delivers 4 J energy, 144 fs long laser pulses with an ultra-high
temporal contrast of 5× 10
12
for the ASE, which is achieved using a so-called double chirped-pulse amplification scheme
and cross-polarized wave generation pulse cleaning. By tightly focusing, the peak intensity exceeds 3.5 × 10
20
Wcm
−2
.
These parameters predestine POLARIS as a scientific tool well suited for sophisticated experiments, as exemplified by
presenting measurements of accelerated proton energies. Recently, an additional amplifier has been added to the laser
chain. In the ramp-up phase, pulses from this amplifier are not yet compressed and have not yet reached the anticipated
energy. Nevertheless, an output energy of 16.6 J has been achieved so far.
Keywords: design; high power laser; laser amplifiers; laser plasmas interaction; laser systems; modelling; optimization; ultra-intense; ultra-
short pulse laser interaction with matter
1. Introduction
Chirped-pulse amplification (CPA
[1]
) laser systems with
output powers of several terawatts or even petawatts, which
can be focused to intensities in excess of 10
22
Wcm
−2
are
widely used to study laser–matter interactions. During the
past three decades this field of science has been growing
rapidly and it has been shown that the laser performance
in terms of pulse duration, pulse energy, and temporal
intensity contrast strongly affects the experimental results.
Experiments of particular interest are electron
[2, 3]
or ion
acceleration
[4]
, the laser-based generation of X-rays
[5]
, high-
energy physics
[6]
or laser-based proton radiography
[4, 7]
.
The community interested in these high-intensity phe-
nomena is spread worldwide, operating several dozens
of high-intensity lasers, the majority of which are based
on direct (e.g., for Nd:Glass-systems) or indirect (e.g.,
for Ti:Sapphire-systems, which are pumped by flashlamp-
pumped frequency-doubled Nd:YAG Lasers) pumping of the
active material by flash lamps.
Correspondence to: Dr. Marco Hornung, Helmholtz-Institute Jena,
Fr
¨
obelstieg 3, 07743 Jena, Germany. Email: Marco.Hornung@uni-jena.de
However, for more than one decade strong efforts have
been made to establish diode-pumped solid-sate laser
(DPSSL) technology for generating high-energy femtosec-
ond or picosecond laser pulses
[8]
. The most commonly used
Yb
3+
-doped amplification media have already been used for
the amplification of ns-laser pulses to energies in excess of
10 J, as recently shown in the projects LUCIA (Yb:YAG,
14 J
[9]
), DIPOLE (Yb:YAG, 10 J
[10]
), and MERCURY
(Yb:S-FAP, 55 J
[11]
). Furthermore, a number of projects
have started to investigate and to develop high-energy class
DPSSLs (HECDPSSL) all over the world
[12]
.
At the Helmholtz-Institute and the Institute of Optics and
Quantum Electronics in Jena, Germany, the POLARIS laser
system
[13]
has been developed and commissioned during
the past decade. It has commenced its daily operation.
Within its experimental program, more than 16,000 shots
have been delivered on target during the past two years.
The POLARIS project was started in 1999 in order to
develop a high-intensity HECDPSSL which could be used
in laser–matter interaction experiments. The current key
parameters of POLARIS are: 1030 nm centre wavelength,
up to 6.5 J pulse energy (4 J on target), 144 fs pulse duration,
7.1 μm
2
focal-spot size, and a temporal contrast for the
1
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