CO 2 Laser
CO2 Laser Amplifier
To reach a power level needed for laser accelerator studies,
the sliced picosecond CO2 laser pulse is amplified 104-105
times. A 3-atm CO2 amplifier with the active volume of 120x5x2
cm3 pumped by a UV-preionized 150-kV transverse electrical
discharge serves for that purpose. The amplifier optical setup consists
of two parts: regenerative and multi-pass. With a help of two quarter-wave
Pockels cells the injected laser pulse is trapped inside the regenerative
cavity and is extracted after the controlled number of double passes (normally
five). The output energy is limited by the damage threshold of the Pockels
crystal to ~10 mJ. However, this brings the output only part ways towards
the desired power level. The four extra passes through the amplifier are
arranged in a double-X configuration using a 4-mirror set-up, as shown
in Figure. We must address the problem of preventing parasitic self-lasing
caused by the extremely high gain conditions. This problem is solved by
placing a saturable absorber cell and a plasma switch in the way of the
regeneratively amplified beam before redirecting it for the next four
passes through the amplifier. The dense plasma of the laser spark, created
at the focal point of a telescope inside the plasma switch, blocks the
passage of parasitic radiation recycling through the amplifier. The plasma
breakdown also shortens the width of the amplified pulse.
Ultimately, after 4 additional passes through the same
amplifier we measure an output laser energy of 1 J. A single-shot autocorrelator
indicates that the laser pulse width is 100 ps, which corresponds to the
spectral-bandwidth-limited minimum pulse duration sustainable by the 3-atm
CO2 amplifier. The corresponding peak power is 10 GW.
Last Modified: December 3, 2007
Please forward all questions about this site to:
Vitaly Yakimenko
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