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1
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2
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- 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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3
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- 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
- Amplified beam is compressed to 25fs
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4
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5
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- How does the 790nm beam gain energy?
- The pump laser excites the atoms in the Ti:Sapphire 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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6
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- 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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7
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8
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9
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10
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11
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- 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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12
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- Disaster: Pump Laser broke down
- More Problems:
- Sapphire Crystal cut wrong
- Ion pump not manufactured yet
- Manufacturing problems with pump mirrors and retro mirrors, telescope
mirrors
- Everything but one telescope lens has arrived, end of Aug.
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- Major components:
- Steps to complete:
- Align components
- Use uncompressed beam to optimize and test
- Use the FROG to estimate resulting pulse width
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14
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- Grating Alignment Criteria: grooves must be perpendicular to the table
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15
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- Periscope Alignment Criteria: beam entering parallel, exits parallel
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16
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17
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- 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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18
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- 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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19
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- Optimizing 2nd order dispersion:
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- Optimizing 3rd order dispersion:
- Checking parallelism between the gratings
- The spectrum of the compressed beam should be circular
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21
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22
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- FROG (Frequency Resolved Optical Gating) Estimation:
- Gives a 2D array combining information of time and wavelength called a
spectrograph
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23
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- Dr. Chang, Dr. Weaver, Dr. Corwin
- SUROP – Dr. Shanklin, Amelia Asperin
- KLS Group
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24
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- Diffraction Gratings Brochure. Optometrics Corporation. 28 July 2006.
PDF File. <http://www.optometrics.com/prod/spectro/gratings/
gratingbrochure.pdf>
- Kansas Light Source. 10 February 2006. Kansas State University. 23 July
2006. <http://jrm.phys.ksu.edu/lasers .html>.
- Paschotta, Dr. Rüdiger. Chirped Pulse Amplification. 06 June 2006. RP
Photonics Consulting. 23 July 2006. <http://www.rp-photonics.com
/chirped_pulse_amplification.html>.
- Pulse Compression Gratings. Newport Corporation. 23 July 2006. <http://www.newport.com/store/genproduct.aspx?
lone=Diffraction-Gratings&id=5271&lang=1033>.
- Siegman, Anthony E. Lasers. University Science Books. Sausalito,
California: 1986.
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25
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- 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
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26
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- Methods of measuring spot size
- Create ratio, it remains constant
- Ratio : 0.01195 mm/pixel
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27
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28
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Notes