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

2. 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.”

3. 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

4. Kansas Light Source Sample setup Pulse Source Stretcher Gratings
Amplifier
Pulse Source
Stretcher
Final Beam
Gratings
Compressor

5. Kansas Light Source 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

6. 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

7. Kansas Light Source
What are gratings?

8. KLS Upgrade Darwin 527 nm Pump Laser Legend: M – Mirror L – Lens
Ion Pump M6 M4 L3 L6 M2 M3 L2 L1 M5
BS1 L4 L5
Darwin 527 nm
Pump Laser
Legend:
M – Mirror
L – Lens
BS – Beam Splitter M1

9. KLS Upgrade 1mm spot size Pump Beam 25.4mm Crystal Diverging Lens
Collimating Lens
Converging Lens

10. KLS Upgrade From Amplifier 1 Final Beam Compressor Darwin 527 nm
RM1
M13
PM1
PM2
RM2 M6
RM4 M4
Ion Pump M7 L3 L6
Pockel’s Cell
RM3
Telescope M2 M3 L2 L1
From Amplifier 1
M10 M5
BS1 L4 L5 M9 P2 G1 G2 P1
Compressor
Final Beam M8
Darwin 527 nm
Pump Laser
Legend:
M – Mirror
L – Lens
RM – Retro Mirror
PM – Pump Mirror M1

11. Pump Laser System
Darwin 527 nm
Pump Laser M4 M2 L1 L2 M3 M6 M5
BS1 L4 L5 M1 L6 L3
Ion Pump
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.

12. Pump Laser System Disaster: Pump Laser broke down More Problems:
Delay: Next week
More Problems:
Sapphire Crystal cut wrong
Delay: End of August
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.

13. 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

14. Compressor Construction
Grating Alignment Criteria: grooves must be perpendicular to the table
= Iris
Mirrors
Laser
Grating
Same height
for alignment

15. Compressor Construction
Periscope Alignment Criteria: beam entering parallel, exits parallel

16. Compressor Construction
VND
Periscope
Final Beam
CCD CAM
Beam Height = 5”
Gratings
Periscope
Beam Height = 5”
Beam Height ≈ 3.85”

17. 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

18. 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

19. Compressor Construction
Optimizing 2nd order dispersion: P2 G2 P1 G1
Point of white light and noise M9

20. 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

21. Compressor Construction

22. 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: fs
Spectral Width: 44.84nm l t

23. THANK YOU!! Dr. Chang, Dr. Weaver, Dr. Corwin
SUROP – Dr. Shanklin, Amelia Asperin
KLS Group

24. Sources
Diffraction Gratings Brochure. Optometrics Corporation. 28 July PDF File. < gratingbrochure.pdf>
Kansas Light Source. 10 February Kansas State University. 23 July < .html>.
Paschotta, Dr. Rüdiger. Chirped Pulse Amplification. 06 June RP Photonics Consulting. 23 July < /chirped_pulse_amplification.html>.
Pulse Compression Gratings. Newport Corporation. 23 July < lone=Diffraction-Gratings&id=5271&lang=1033>.
Siegman, Anthony E. Lasers. University Science Books. Sausalito, California: 1986.

25. 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

26. Kansas Light Source Methods of measuring spot size
Create ratio, it remains constant
Ratio : mm/pixel
492 pixels
510 pixels
CCD Cam Screen
8.47 mm

27. Compressor Construction

28. Compressor Construction