Production of ultrashort, ultrahigh-intensity laser pulses using Chirped
Pulse Amplification (CPA) method and higher-order harmonic generation.

Lukasz Brzozowski



When trying to amplify a laser light in a conventional master-oscillator
power-amplifier system a small prototype laser pulse is passed through a
series of optical amplifiers.  If a high-power is to be obtained the
pulse is amplified until one of the nonlinear effects is encountered. The
reason for that is that the index of refraction of materials tends
to display dependence on the intensity for high intensities.  The
nonlinear effects most common are self-focusing, filamentation and
self-phase modulation.  I shall explain from the physical point of
view how those effects originate. Another problem with achieving
high-power pulses with the conventional methods is that high power pulses
inside the amplifier tend to damage the interanal components.  The CPA
methods gets around all those problems by first stretching the short low
energy pulse, then amplifying the long pulse and then compressing the long
high energy pulse to an ultrashort, ultrahigh intensity pulse.  The
advantage of this method is that there never is an ultrahigh intensity
pulse oscillating and amplified.  Thus this presents remedy for the
nonlinear effects mentioned above.  I shall describe what are the
components of a CPA system, how the pulse is stretched and separated into
different frequences and how it is then compressed. The ability to produce
ultrafast, ultrahigh intensity pulses allows the the generation of
high-order UV harmonics.  I shall outline how the number of possible
harmonics produced depends on the intensity and pulse duration of the laser
pulse.


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