Unconventional Laser Guide Stars and Wavefront Correction of Blue Starlight

• Main Author: Hellwarth, Robert W
• Format: Report
• Language: English
• Subjects: ADAPTIVE OPTICS; Astronomy; CELESTIAL GUIDANCE; CORRECTIONS; GUIDE STARS; LASER APPLICATIONS; LASER GUIDANCE; LASER GUIDE STARS; Lasers and Masers; LIGHT MODULATORS; LIGHT PULSES; MAXWELLS EQUATIONS; Optics; RAMAN SCATTERING; STARLIGHT; ULTRAVIOLET LASERS; WAVEFRONTS

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.