Optical amplifiers: Highest peak power and excellent stability
Record parameters for amplified ultrashort pulses
Date:
July 6, 2020
Source:
Forschungsverbund Berlin
Summary:
Optical amplifiers based on chirped pulse amplification (CPA)
are used to generate high intensity pulses. In the CPA scheme, a
weak temporally stretched seed pulse is amplified to high energy
in a laser amplifier and finally re-compressed resulting in an
ultrashort pulse of very high intensity.
FULL STORY ========================================================================== Power-scalable ultrafast laser sources in the midwave-infrared (MWIR) are
a key element for basic research and applications in material processing
and medicine. Optical amplifiers based on chirped pulse amplification
(CPA) are used to generate high intensity pulses, a technique awarded with
the Nobel Prize in physics in 2018. In the CPA scheme, a weak temporally stretched seed pulse is amplified to high energy in a laser amplifier
and finally re- compressed resulting in an ultrashort pulse of very
high intensity. Applying this concept a new system was developed at MBI delivering few-ps pulses at 2 mym wavelength with peak power beyond 10
GW (10 billion watt) at a 1 kHz repetition rate. The emitted pulses are characterized by excellent stability and brilliant beam quality. The
results are reported in the latest issue of Optics Letters (Optics
Letters 45, 3836 (2020)).
==========================================================================
The main amplifiers of the 2-mym CPA system are based on Ho:YLF crystals
and consist of a highly stable regenerative amplifier and two booster amplifiers.
All of them are operated at room temperature and pumped by continuous-wave
Tm: fiber lasers with a total power of 270 W. Starting from a 2-mym supercontinuum source the seed pulses are stretched and pre-amplified and subsequently fed into the Ho:YLF amplifier chain.The re-compressed pulse
energy of the Ho:YLF CPA amounts to 52.5 mJ and reveals an excellent pulse-to-pulse stability of <0.23% rms. The long-term pulse stability
together with the beam quality, measured to be better than a M2 of
1.2. The emitted spectrum centered at 2050 nm with a bandwidth of 3.5 nm
(FWHM) supports a ~1.7 ps Fourier-transform limited pulse duration. After amplification the pulses are re-compressed in a Treacy-type grating
arrangement with an efficiency >93%. The recorded autocorrelation
trace exhibits a FWHM of 4.1 ps. This corresponds to a duration of the
main pulse of 2.4 ps (FWHM) with an estimated energy content of 85%, translating into 17 GW peak power. The latter and the pulse energy of
50 mJ represent the highest values ever achieved for few-ps pulses at
2 mym wavelength yet.
This source is currently being applied as pump in a system for the
generation of few-cycle pulses around 5-mym with multi-millijoule
energies. Applications in nonlinear optics, spectroscopy and materials processing are underway.
========================================================================== Story Source: Materials provided by Forschungsverbund_Berlin. Note:
Content may be edited for style and length.
========================================================================== Journal Reference:
1. Lorenz von Grafenstein, Martin Bock, Dennis Ueberschaer, Azize
Koc,, Uwe
Griebner, Thomas Elsaesser. 205  mym chirped pulse
amplification system at a 1  kHz repetition rate--
24  ps pulses with 17  GW peak
power. Optics Letters, 2020; 45 (14): 3836 DOI: 10.1364/OL.395496 ==========================================================================
Link to news story:
https://www.sciencedaily.com/releases/2020/07/200706113926.htm
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