Thank you tremendously, Steve! I was hoping someone like you might enlighten us.
Could you perchance elaborate on outdoor scientific lasing requirements with the FAA? This area interests me greatly as I have done a lot of free space optical / lightwave communications and other such non lasershow activities (and yes, I'm FCC licensed).
640 Terahertz (light) is a grey area. Yes, the FCC allows it under a guise in the wording, ARRL recognizes it, but FCC and FAA do NOT have a memorandum on this. So, Skyscatter/Cloudscatter is out of the question without filing with FAA. Direct paths between buildings or mountaintops are another matter.
FAA's rule, if a helicopter can get into the beam, you should file. If your in navigable airspace you should file.
Common sense, if your following your spirit of your license and running minimum usable power/QRP , Your on a tripod, and your not using more then say 50 mW, I would not worry about it. Most laser distance records were set using CW and milliwatts anyways.
However if you start getting to the point where the NOHD is more then a hundred yards, etc, Its time to start thinking seriously about complying with the rules. Keep in mind you have the sensitive flight zone and critical flight zone exposure distances to think about as well. Google "lasers in airspace, FAA" and the calculations will pop up, I'm thinking its 7400.2 G for the latest revision,
If your running power levels (watts) where scatter is visible some distance away from the laser, keep in mind pilots are obliged to report you if they can see the beam.
Upcollimation to reduce power per unit area is a very good idea.
Consider using LEDs, you'll get more range, as laser beams are subject to horrible interference effects beyond a few kilometers. Incoherent light actually wins in this case.
Some of the current world records for light communications was set with Luxeon Stars, with Fresnel Lenses, not with lasers. Over a few kilometers, lasers really "suck" for lightwave communications with any bandwidth , unless your in a vacuum or using fiber optics.
The current laser record was set with a Hecad, but bandwidth over the long path was found to fall to near ON/OFF, a few Hertz at best.
If you have a incident, your probably wide open for prosecution on this, callsign issued or not.
Alternatives for Laser, See:
http://www.google.com/url?sa=t&rct=...=hkGJTsB3zyCvt7ZR4bfjAw&bvm=bv.69837884,d.aWw
Modulatedlight.org
Steve