Kansas Light Source Upgrade

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Kansas Light Source Upgrade
Scott Palmiter Mentor Dr. Zenghu Chang Lab
Partner Jason Tackett
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Kansas Light Source

• What is the KLS?
• Ultrafast High Intensity Laser Facility
• Provides very short pulses
• Pulse Duration 25fs
• On the order of molecular oscillations
• Wavelength 790nm (Infrared)
• Pulse Energy 2.5mJ
• Used for studying the fastest dynamics in atoms,
  molecules and other matter under the influence of
  strong electric fields.

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Kansas Light Source

• How does the KLS work?
• Seed pulses with 1nJ at 10fs are stretched to
  100ps
• Avoids damage to amplifying crystal
• With each successive pass through the crystal,
  the beam gains energy up to 2.5mJ
• 14 total passes
• Amplified beam is compressed to 25fs

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Kansas Light Source

• Sample setup

Gratings
Compressor
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Kansas Light Source

• How does the 790nm beam gain energy?
• The pump laser excites the atoms in the
  TiSapphire crystal to a higher excited state
  creating a population inversion
• As the infrared beam passes through the media, it
  stimulates the atoms and lowers their energy
  states. As the atoms change energy states,
  photons are ejected and picked up by the passing
  beam

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Kansas Light Source

• How does the 790nm beam gain energy?
• Each pass has more photons, and subsequently
  causes the ejection of more photons, amplifying
  the beam

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Kansas Light Source

• What are gratings?

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KLS Upgrade
M6
M4
L6
L3
M2
M3
L2
L1
M5
BS1
L4
L5
Darwin 527 nm Pump Laser
Legend M Mirror L Lens BS Beam Splitter
M1
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KLS Upgrade
1mm spot size
Pump Beam
25.4mm
Crystal
Diverging Lens
Converging Lens
Collimating Lens
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KLS Upgrade
M12
M11
RM1
M13
PM1
PM2
RM2
M6
RM4
M4
Ion Pump
M7
L6
L3
RM3
Telescope
M2
M3
L2
L1
From Amplifier 1
M5
M10
BS1
L4
L5
Final Beam
M8
Darwin 527 nm Pump Laser
Legend M Mirror L Lens RM Retro Mirror PM
Pump Mirror
M1
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Pump Laser System

• Began building the lens-mirror system to achieve
  1mm spot size at future location of crystal.
• Practiced enlarging, collimating, and converging
  to desired size.

• Learned convention of measuring spot size.

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Pump Laser System

• Disaster Pump Laser broke down
• Delay Next week
• More Problems
• Sapphire Crystal cut wrong
• Delay End of August
• Ion pump not manufactured yet
• Delay End of August
• Manufacturing problems with pump mirrors and
  retro mirrors, telescope mirrors
• Everything but one telescope lens has arrived,
  end of Aug.

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Compressor Construction

• Major components
• Gratings
• Periscopes
• Steps to complete
• Align components
• Use uncompressed beam to optimize and test
• Use the FROG to estimate resulting pulse width

Final Beam
P2
G2
P1
WP
G1
Amplified Beam
M9
Legend M Mirror P Periscope G Grating WP
Half wave plate
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Compressor Construction

• Grating Alignment Criteria grooves must be
  perpendicular to the table

Same height for alignment
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Compressor Construction

• Periscope Alignment Criteria beam entering
  parallel, exits parallel

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Compressor Construction
Periscope
VND
Final Beam
CCD CAM
Beam Height 5
Gratings
Periscope
Beam Height 5
Beam Height 3.85
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Compressor Construction

• Checking Polarization
• Must make sure polarization of incident beam on
  the gratings is correct
• Check by finding the setting on half wave plate
  that would give us maximum intensity
• Easiest with zero order

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Compressor Construction

• Optimizing 2nd order dispersion
• Finding correct distance between gratings
• Using a very small focal length lens (30mm),
  white light is generated and the oscillations in
  the in the air caused by the laser create noise
• Find the brightest light and loudest noise level

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Compressor Construction

• Optimizing 2nd order dispersion

P2
G2
P1
Point of white light and noise
G1
M9
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Compressor Construction

• Optimizing 3rd order dispersion
• Checking parallelism between the gratings
• The spectrum of the compressed beam should be
  circular

P2
G2
P1
G1
M9
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Compressor Construction
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Compressor Construction

• FROG (Frequency Resolved Optical Gating)
  Estimation
• Gives a 2D array combining information of time
  and wavelength called a spectrograph

Resulting estimations Pulse Width 29.91
fs Spectral Width 44.84nm
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THANK YOU!!

• Dr. Chang, Dr. Weaver, Dr. Corwin
• SUROP Dr. Shanklin, Amelia Asperin
• KLS Group

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Sources

• Diffraction Gratings Brochure. Optometrics
  Corporation. 28 July 2006. PDF File.
  lthttp//www.optometrics.com/prod/spectro/gratings/
  gratingbrochure.pdfgt
• Kansas Light Source. 10 February 2006. Kansas
  State University. 23 July 2006.
  lthttp//jrm.phys.ksu.edu/lasers .htmlgt.
• Paschotta, Dr. Rüdiger. Chirped Pulse
  Amplification. 06 June 2006. RP Photonics
  Consulting. 23 July 2006. lthttp//www.rp-photonics
  .com /chirped_pulse_amplification.htmlgt.
• Pulse Compression Gratings. Newport Corporation.
  23 July 2006. lthttp//www.newport.com/store/genpro
  duct.aspx? loneDiffraction-Gratingsid5271lang
  1033gt.
• Siegman, Anthony E. Lasers. University Science
  Books. Sausalito, California 1986.

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Kansas Light Source

• Methods of measuring spot size
• Create a ratio of length to pixels.
• Multiply be number of pixels the beam takes up.
• Ratio changes every time the CCD is moved

View of CCD
Known distance
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Kansas Light Source

• Methods of measuring spot size
• Create ratio, it remains constant
• Ratio 0.01195 mm/pixel

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Compressor Construction
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Compressor Construction