[Laser] Laser comm stuff

[J. Forster]

Your findings roughly parallel mine of the early 70s. I used a PMT, preamp, and
spectrum analyzer (Tek 7L5) to look at a slightly overcast sky through a local
telescope with the possible objective of filtering out or gating the PMT to
eliminate street light interference with photoelectric astronomy.

The harmonics were visible up to hundreds of Hz. In those days Hg was the most
used type. The light output does not follow the line exactly because there is a
bit of an afterglow.

Also, interestingly, the phase varies depending on where you are pointing
because power is 3 phase.

-John