DAZZLER vs LCSLM

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DAZZLER vs LC-SLM custom pulse shaping _at_ SPARC

• SPARC Photo-injector Laser Team
• C.Vicario, M. Petrarca, S. Cialdi, A. Ghigo

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SPARC laser system

• A TiSa TW-class laser is used to drive the SPARC
  RF-gun.
• The flat top pulse shape is achieved using two
  steps
• the Dazzler or LC-SLM for amplitude and phase
  modulation in IR before the amplifier
• UV pulse shaper for amplitude modulation to get
  shorter rise time

Opt. Lett. 31, 19 (2006) 2885-2887
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Dazzler LC-SLM
Into amplifier
60 cm

From oscillator
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Features

• DAZZLER
• Compact
• Easy alignment
• Contemporary phase and amplitude modulation
• Losses within 50
• Resolution 0.3 nm
• Slow optimization

• LC-SLM
• Not-compact
• Tricky alignment
• Phase or amplitude modulation
• Losses within 50
• Resolution better than 0.1 nm
• Fast optimization

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The UV time profiles performed by the the two
shapersDAZZLER
LC-SLM

Rise and fall time 2.6 ps
Rise and fall time 2 ps
To obtain faster rise and fall time values
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Shaping device CUSTOM UV pulse shaper
-The UV stretcher was designed to lengthen the
laser pulse up to 20 ps. -In the Fourier plane
an amplitude filter, such as an iris, can be
applied to cut the tails of an almost square
spectrum produced bu the DAZZLER or LC-SLM, the
obtained spectrum profile is transferred into the
time profile by the stretcher -In the apparatus
an on-line spectrometer is integrated.
Picture of the apparatus
Spectrom CCD
Filter plane
Focusing lenses
input
output
Grating pair
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CUSTOMPulse shaping without the DAZZLER
When a proper sharp cut is applied to the natural
UV Gaussian laser spectrum a flat top profile in
time is produced. 1 results are comparable to the
two stages pulse shaping. 2 the minimum rise time
limited by the bandwidth (see figure)? 3 The UV
stretcher have 20 higher energy losses but are
much more cheap and simple respect to the other
IR pulse shapers The rise and fall time are
reduced to 1.5 ps.
Cut
No-cut
Simulated rise time vs input bandwidth
Spectra
Time
Appl. Opt. 46, 22 (2007) 4959-4962
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Electron experimental results
The flat top pulse shape allowed the observation
of the double-minimum emittance evolution at
SPARC.
UV LASER cross correlation measurement
Accepted for publication in PRL