Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Kansas Light Source Upgrade Scott Palmiter Mentor: Dr. Zenghu Chang Lab Partner: Jason Tackett 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.” 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 Kansas Light Source • Sample setup Pulse Source Stretcher Amplifier Final Beam Gratings Compressor 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 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 Kansas Light Source • What are gratings? KLS Upgrade M6 M4 Ion Pump L3 L6 M2 M3 L2 L1 M5 BS1 Legend: M – Mirror L – Lens BS – Beam Splitter M1 L4 L5 Darwin 527 nm Pump Laser KLS Upgrade 1mm spot size Pump Beam 25.4mm Crystal Diverging Lens Collimating Lens Converging Lens KLS Upgrade M12 M11 RM1 M13 PM1 PM2 RM2 M6 RM4 M4 Ion Pump M7 L3 L6 Pockel’s Cell RM3 Telescope M2 M3 L2 L1 M10 From Amplifier 1 M5 BS1 L4 L5 P2 Final Beam Legend: M – Mirror L – Lens RM – Retro Mirror PM – Pump Mirror G2 P1 Compressor M8 G1 M9 M1 Darwin 527 nm Pump Laser Pump Laser System • Began building the M4 lens-mirror system to L3 achieve 1mm spot size at future location M3 of crystal. L2 L1 • Practiced enlarging, collimating, and converging to desired size. • Learned convention Ion of measuring spot Pump size. M6 L6 M2 M5 BS1 M1 L4 L5 Darwin 527 nm Pump Laser 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. Compressor Construction • Major components: – Gratings – Periscopes Final Beam • Steps to complete: – Align components – Use uncompressed beam to optimize and test – Use the FROG to estimate resulting pulse width P2 G2 P1 WP G1 M9 Legend: M – Mirror P – Periscope G – Grating WP – Half wave plate Amplified Beam Compressor Construction Grating Alignment Criteria: grooves must be perpendicular to the table Mirrors = Iris Same height for alignment Laser Grating Compressor Construction Periscope Alignment Criteria: beam entering parallel, exits parallel Compressor Construction VND Final Beam CCD CAM Beam Height = 5” Gratings Periscope Beam BeamHeight Height=≈5” 3.85” Periscope 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 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 Compressor Construction Optimizing 2nd order dispersion: P2 G2 P1 G1 Point of white light and noise M9 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 Compressor Construction Spectra of Amplified Beam Before and After Compression 1.2 1 Intensity 0.8 0.6 After Before 0.4 0.2 0 -0.2700 750 800 Wavelength (nm) 850 900 Compressor Construction FROG (Frequency Resolved Optical Gating) Resulting estimations: Estimation: Pulse Width: 29.91 fs – Gives a 2D array combining information of time and Spectral Width: 44.84nm wavelength called a spectrograph t l THANK YOU!! • Dr. Chang, Dr. Weaver, Dr. Corwin • SUROP – Dr. Shanklin, Amelia Asperin • KLS Group Sources 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=DiffractionGratings&id=5271&lang=1033>. Siegman, Anthony E. Lasers. University Science Books. Sausalito, California: 1986. Kansas Light Source Methods of measuring spot size View of CCD Known distance – Create a ratio of length to pixels. – Multiply be number of pixels the beam takes up. – Ratio changes every time the CCD is moved Kansas Light Source Methods of measuring spot size – Create ratio, it remains constant – Ratio : 0.01195 mm/pixel CCD Cam Screen 492 pixels 510 pixels Compressor Construction Spectrum Before Compression 1200 Intensity 1000 800 600 400 200 0 -200700 750 800 Wavelength (nm) 850 900 Compressor Construction Spectrum After Compression 300 250 Intensity 200 150 100 50 0 -50700 750 800 Wavelength (nm) 850 900