EditAttachPrintable
r27 - 08 May 2009 - 18:25:02 - CelineDorgevilleYou are here: TWiki >  CfAO Web  > SodiumLaserGuidestars

Sodium Laser Guidestar Page

Sodium wavelength lasers are critical to the next generation of adaptive optics for ground-based astronomical telescopes. Important issues are:

  • Understanding the physics of the sodium layer / laser photon interaction in order to optimize the usable wavefront reference return signal
  • Considerations of cost, size, and power consumption in order to make it feasible to field such lasers at mountaintop astronomical observatories
  • Controlling Rayleigh backscatter and "fratricide" which is a noise source to the wavefront sensing
  • Obtaining high laser wavefront quality and engineering the laser projection system to form the smallest possible guide star spot on the sodium layer

Summary of Sodium Laser Guide Stars now "On-the-Sky" - Please use standard Guidelines in reporting return measurements

(in no particular order)
Numbers in the table are approximate or typical. See the references for more details.

Facility Principal Investigators Laser Maker and Type Return / Watt (Details) Average Power Spot Size (apparent) Pulse & Spectral Format Web Link
Lick Mt. Hamilton Claire Max, Don Gavel LLNL Tunable Dye 10 ph/s/cm2/W 12 W 2 arcsec 100 ns, 11 kHz, 2 GHz EO modulated LGS project at LLNL and instrumentation pages at Lick and SPIE paper
Starfire Optical Range Bob Fugate, Craig Denman SOR Solid state, resonant sum-frequency generator 100 ph/s/cm2/W seasonal average 50 W seeing limited 1.4-3 arcsec (site has r0=7.8cm avg) CW 10 kHz line SPIE article and Craig Denman's talk at the Nov 2006 LaserWorkshop
W. M. Keck Observatory Peter Wizinowich LLNL Tunable Dye 10 ph/s/cm2/W 12-15 W 1.8" x 2.3" (average stacked) 100 ns, 25 kHz, 2 GHz EO modulated K2LGSAO web, LGS Photometry and SPIE'06 paper (Table 1)
Palomar Richard Dekany, Ed Kibblewhite, Antonin Bouchez University of Chicago Solid state sum-frequency mode-locked 60-80 ph/s/cm2/W 6-8 W 1.8" FWHM arcsec in 1.0 arcsec V-band seeing 1 ns micropulse inside 300 microsec bursts at 300 Hz repetition rate instrumentation page at COO and note on guide star return flux
Subaru Masanori Iye, Yutaka Hayano solid state sum-frequency To be measured 5.4 W at output of laser To be measured ~0.8 ns pulses, 143MHz rep rate, mode-locked (quasi-CW) 1.7GHz bandwidth press release
Gemini North Francois Rigaut, Celine D'Orgeville Lockheed-Martin Coherent Technologies diode-pumped solid state 1.06+1.32micron sum-frequency laser 27photons/cm^2/s/W (laser power projected to the sky, i.e. out of the LLT) with linear polarization (observed ~30% increase with circular polarization at zenith) Photon return measurement made in May 2005, during season of lowest sodium abundance, with ~9W projected to the sky (Note: as of May 2009, ~12 W at the ouput of the laser, ~11W projected to the sky (BTO+LLT throughput ~90%) 1.3 arcsec 0.7 ns pulses, 76 MHz rep rate, mode-locked (quasi-CW), 550MHz bandwidth Altair LGS instrument page and laser commissioning news
Very Large Telescope Domenico Bonaccini Calia Max Planck Institutes Tunable Dye 54 ph/s/cm2/W 10 W 1.25 arcsec CW 3x10 MHz separated by 110MHz press release from VLT, laser specs from MPIE, SPIE article on first light

New Laser Development

Institution Principal Investigators Sponsor Laser Type Progress Reference
Lockheed-Martin Coherent Technologies Allen Tracy, Allen Hankla AODP Sum frequency solid state, 1319nm+1064nm into PPSLT, modular pulse format 1.5 W / 10 W goal SPIE article
Lawrence Livermore National Laboratory Dee Pennington, Jay Dawson AODP and CfAO Sum frequency fiber, 1583nm+938nm into PPSLT, modular pulse format, 500 MHz linewidth 3.5 W / 5-10 W goal SPIE article
Lockheed-Martin Coherent Technologies LMCT: Ian Lee; Keck: Sean Adkins; Gemini: Celine d'Orgeville Keck I and Gemini South Telescopes Sum frequency solid state, 1319nm+1064nm into LBO, 0.7 nm pulse every 12 ns quasi CW As of May 2009: 40W Keck laser and 50W GS laser demonstrated in the lab, still pending simultaneous demo of other required specs (beam quality, wavelength, power and wavelength stability) SPIE article
European Southern Observatory Domenico Bonaccini Calia ESO Doubled 1178 nm fiber-Raman, modulated CW (to 1 GHz) or Q switched micropulse Demonstrated modulated CW, 4.2 W @ 589 nm Fall 2007 Workshop presentation

Interesting Topics

Discuss these in the blogs below

  • Measurements and comparisons
    • Photometric method and designation of laser return (e.g. photons/sec/cm^2/Watt compared to that of a spectrophotometric star through a narrow band filter referred to the top of the telescope)
    • Laser beam quality (e.g. M^2, apparent FWHM on the sky)
    • Laser output power (e.g. power measured at the output of the laser, power measured or inferred at the output of the launch telescope, is all the power is at the D2 line?, etc.)
    • Methods of independently determining sodium column density (e.g. atoms/m^2)
  • Crucial component development
    • Sum-frequency power crystals – technology advancement, consortium runs, etc.
    • Fibers for high power beam transport to launch telescope – e.g. photonic crystal fibers at Subaru and VLT

Meetings

Contacts List

Name Institution e-mail
Richard Dekany Caltech Optical Observatories rgd@astro.caltech.edu
Don Gavel UC Santa Cruz gavel@ucolick.org
Ed Kibblewhite University of Chicago edk@oddjob.uchicago.edu

Blogs

Please enter your comments and suggestions below. Use the Edit button, scroll to the bottom, type in your blog entry, append your name and date, then click Save. That's all there is to it!

toggleopenShow attachmentstogglecloseHide attachments
Topic attachments
I Attachment Action Size Date Who Comment
pptpps CfAO_Retreat_March_2007.pps manage 8910.5 K 26 Mar 2007 - 17:15 DomenicoBonacciniCalia ESO LGSF status March 2007
Edit | Attach | Printable | Raw View | Backlinks: Web, All Webs | History: r27 < r26 < r25 < r24 < r23 | More topic actions
 
This site is powered by the TWiki collaboration platformCopyright © by the contributing authors. All material on this collaboration platform is the property of the contributing authors.
Ideas, requests, problems regarding TWiki? Send feedback