Laser pointers, cat toys, et all.
The cheap laser diode devices.
Yesterdays high tech is todays toy. These things have
become so common, and cheap, that they no longer really even bear mention,
and certainly are hardly worth the trouble of writing about. The current
generation of laser pointers, pens, cat toys, etc. put out 1 mw or so.
They are gaurantedd to be on sale at any flea market, gun show computer
show, or fair. They are commonly available for under $10, though really
high class models can be had for $25 or so, and professional pen pointers
can cost near $100, and are available with multi color/multi beam options.
All of these devices use laser diodes, an invention
of the eighties. These diodes were intitially meant for use in home devices,
particularly CD players. Most put out a red beam and are vacity lasers,
with microscopic cavities.