the fully diode-pumped Yb:glass laser system POLARIS ... the first generation of high-contrast, 164 fs duration pulses from the laser system POLARIS reaching.
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OPTICS LETTERS / Vol. 38, No. 5 / March 1, 2013
High-intensity, high-contrast laser pulses generated from the fully diode-pumped Yb:glass laser system POLARIS Marco Hornung,1,2,* Sebastian Keppler,2 Ragnar Bödefeld,1,2 Alexander Kessler,1,2 Hartmut Liebetrau,2 Jörg Körner,2 Marco Hellwing,2 Frank Schorcht,1 Oliver Jäckel,1,2 Alexander Sävert,2 Jens Polz,2 Ajay Kawshik Arunachalam,2 Joachim Hein,1,2 and Malte C. Kaluza1,2 1 2
Helmholtz-Institute Jena, Fröbelstieg 3, Jena 07743, Germany
Institute of Optics and Quantum Electronics, Max-Wien Platz 1, Jena 07743, Germany *Corresponding author: marco.hornung@uni‑jena.de Received November 15, 2012; revised January 17, 2013; accepted January 20, 2013; posted January 28, 2013 (Doc. ID 179310); published February 26, 2013
We report on the first generation of high-contrast, 164 fs duration pulses from the laser system POLARIS reaching focused peak intensities in excess of 2 × 1020 W∕cm2 . To our knowledge, this is the highest peak intensity reported so far that has been achieved with a diode-pumped, solid-state laser. Several passive contrast enhancement techniques have been specially developed and implemented, achieving a relative prepulse intensity smaller than 10−8 at t −30 ps before the main pulse. Furthermore a closed-loop adaptive-optics system has been installed. Together with angular chirp compensation, this method has led to a significant reduction of the focal spot size and an increase of the peak intensity. © 2013 Optical Society of America OCIS codes: 140.0140, 140.3295, 140.3480, 320.0320, 320.5520.
Diode-pumped solid-state lasers (DPSSL) have the potential to be compact, energy-efficient, and powerful sources of visible and near-infrared laser radiation [1]. Using Ybdoped active materials suitable for direct diode pumping, such systems reach durations between those of Ti:sapphire systems [2] (τL ≤ 30 fs) and hybrid optical parametric chirped-pulse amplification Nd:glass laser systems [3] (τL ≥ 167 fs). When applying cryogenic cooling schemes, these systems have the potential to generate pulses delivering >150 J energy with 108 at 30 ps) with a duration of 164 fs, which can be focused to peak intensities of 2.4 × 1020 W∕cm2 . To achieve this, several optimization methods were developed and introduced into the system to improve the performance parameters of POLARIS to meet the requirements for experiments on high-intensity laser matter interaction. To our knowledge, this is the highest reported intensity so far generated by a DPSSL. After completing the commissioning of the last amplifier, the expected peak intensity will be increased beyond 1021 W∕cm2 , making POLARIS a scientific tool well suited for sophisticated high-intensity experiments. The research leading to these results has received funding from the European commission’s (EC) 7th Framework Programme (LASERLAB-EUROPE, grant no. 228334) and from the Bundesministerium für Bildung und Forschung (BMBF) (03ZIK445 and 03Z1H531).
x (µm)
Fig. 3. (Color online) Measured spatial and temporal properties of the full amplified laser pulses. (a) Near-field intensity distribution measured in front of the focusing parabola. (b), (d) Transverse far-field profile of the focused laser pulses (d) with and (b) without adaptive optics. (c) Second-order autocorrelation measurement with 1D focused laser pulses. The inset displays the measured sum-frequency signal, where the laser pulse is focused into a beta barium borate crystal.
is larger than I max ∕2. With 164 fs [measured over the full beam profile, cf. Fig. 3(c)] laser pulses delivering up to 4 J on target, a peak intensity of I L 2.4 × 1020 W∕cm2 was achieved. For comparison, we show the focal spot energy distribution in Fig. 3(b), where a plane mirror was used instead of the adaptive mirror while low order aberrations of the wavefront were compensated with the parabolic mirror. Keeping all other parameters constant, the AOS is able to double the peak intensity. The Strehl ratio (I L ∕I C ), defined as the ratio of the achieved peak intensity I L and the calculated peak intensity I C by assuming a flat wavefront, is 0.4. The Strehl ratio is currently limited by residual chromatic aberrations and higher-order wavefront errors. In conclusion, we have shown that the POLARIS system is capable of generating laser pulses of high
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