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Physics and AstronomyAstronomy

Unconventional Laser Guide Stars and Wavefront Correction of Blue Starlight

Authors: Robert W. Hellwarth; UNIVERSITY OF SOUTHERN CALIFORNIA LOS ANGELES DEPT OF ELECTRICAL ENGINEERING
 
Abstract: In this project we established by theory and experiment (1) that a 1/ 4 Joule, 20 ns, ultraviolet laser pulse could create (near 20 km altitude) a return signal to the transmitting telescope that would appear, for 20 ns, to have a brightness temperature of millions of degrees, and thus serve as a guide star for high-order corrections of blue starlight, (2) that a much lower energy (approx. one hundred microjoules) femtosecond laser pulse could create an upward-traveling pulse near the tropopause with its wavelength shifted from the driving pulse, (3) that exact, finite-energy, pulse solutions of Maxwell's equations can have an electric (or magnetic) field with zero y-component everywhere in space, (4) that Maxwell's equations place no limit on the smallness of extinction experienced by a focused pulse of finite energy passing through finite crossed polarizers, and (5) that wavefront correctors based on photo-refractive spatial-light-modulators are unlikely to have their speed-of- response improved.

Limitations: APPROVED FOR PUBLIC RELEASE
Description: Final rept.
Pages: 10
Report Date: 28 MAY 2002
Contract Number: F49620-98-1-0374
Report Number: A269704
Keywords relating to this report:
*ADAPTIVE OPTICS
*LASER GUIDANCE
CELESTIAL GUIDANCE
CORRECTIONS
LASER APPLICATIONS
LIGHT MODULATORS
LIGHT PULSES
MAXWELLS EQUATIONS
RAMAN SCATTERING
STARLIGHT
ULTRAVIOLET LASERS
WAVEFRONTS
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