Mp. Jelonek et al., CHARACTERIZATION OF ARTIFICIAL GUIDE STARS GENERATED IN THE MESOSPHERIC SODIUM LAYER WITH A SUM-FREQUENCY LASER, Journal of the Optical Society of America. A, Optics, image science,and vision., 11(2), 1994, pp. 806-812
We generated resonant-fluorescent artificial guide stars in the Earth'
s mesospheric sodium layer with an 840-Hz, 10-mJ sum-frequency laser o
perating at 589 nm and have conducted experiments to characterize the
guide stars for use as beacons for atmospheric compensation with adapt
ive optics. We made high-resolution images with a 1.5-m telescope and
CCD camera with exposures from 0.1 to 10.1 s of spots as small as 1.64
times the diffraction limit. We also used an intensified charge-injec
tion-device camera to record live video at frame rates of 30 Hz. Using
a photomultiplier tube with both the 1.5-m telescope and a 14-in. tel
escope, we collected temporal data and calculated the sodium-layer col
umn densities of 2-3 x 10(13)/m(2) from long pulse measurements. We ha
ve observed the phenomenon of optical pumping of the sodium layer by p
ropagating circularly polarized light at peak power densities incident
on the layer of 1.0 mW/cm(2). Propagating circularly polarized light
gives a 41-48% increase in fluorescent return signal over linearly pol
arized light. Artificial guide stars are suitable for atmospheric comp
ensation with the use of adaptive optics.