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Optimization of Sodium Guide Star Return using Polarization and/or Modulation Control

Award Information
Agency: Department of Defense
Branch: Air Force
Contract: FA9451-19-P-0671
Agency Tracking Number: F19A-008-0200
Amount: $149,999.00
Phase: Phase I
Program: STTR
Solicitation Topic Code: AF19A-T008
Solicitation Number: 19.A
Solicitation Year: 2019
Award Year: 2019
Award Start Date (Proposal Award Date): 2019-07-15
Award End Date (Contract End Date): 2020-07-15
Small Business Information
2041 Tapscott Avenue
El Cerrito, CA 94530
United States
DUNS: 967821724
HUBZone Owned: No
Woman Owned: No
Socially and Economically Disadvantaged: No
Principal Investigator
 Simon Rochester
 (510) 206-6586
Business Contact
 Dmitry Budker
Phone: (510) 541-5500
Research Institution
 The Regents of the University of California
 Kate Lewis Kate Lewis
c/o Sponsored Projects Office 1608 Fourth Street, Suite 220
University of California, Berkeley, CA 94710
United States

 (510) 643-5997
 Nonprofit College or University

Large ground-based telescopes require adaptive optics (AO) to correct for distortions introduced by atmospheric turbulence. In order to function, the AO system must track a bright point source. Although a natural star may be used, full sky coverage requires an artificial beacon created with a laser. The most common type of laser guide star (LGS) employs the mesospheric layer of sodium atoms at an altitude of ~90 km; a laser at 589 nm excites the Na atoms on the D2 line and the subsequent fluorescence is observed. Because of the small collection solid angle afforded by a ~1 m diameter telescope at a distance of ~90 km, returned photons from the Na LGS are at a premium. A possible way to optimize a Na LGS is amplitude or polarization modulation of the laser beam. For several reasons, photon return is enhanced by optical pumping of the Na atoms. However, the presence of the geomagnetic field can limit the effectiveness of optical pumping by inducing Larmor precession, which effectively depolarizes the atoms. Synchronous pumping via modulated light can counteract this effect, thus enhancing photon return. We propose to investigate, using computer simulations, various modulation schemes for enhancing return.

* Information listed above is at the time of submission. *

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