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From: agn@unh.cs.cmu.edu (Andreas Nowatzyk)
Newsgroups: sci.electronics
Subject: Re: Looking for cheap visible red laser diodes
Keywords: laser diode red
Message-ID: <7377@pt.cs.cmu.edu>
Date: 21 Dec 89 00:55:06 GMT
References: <2290@sactoh0.UUCP> <1237@mit-amt.MEDIA.MIT.EDU> <1975@eric.mpr.ca>
Organization: Carnegie-Mellon University, CS/RI
Lines: 33

>Mark A. Haun asks for cheap, VISIBLE laser diodes
>Adam Glass gives source for a 7-25W IR laser diode
>David LeBlanc is puzzled by the 25W spec

25W IR laser diods are for real, and if you read through the rest of
the posted specs, you'll find that the other data (lasing current and
voltage drop) are in line. The 25W part is not a typo. In fact, you can
buy IR laser diode arrays with more than 1KW output.

Such devices are not used in fiber optic communications or CD players
(obviously). Applications for high power laser diods include range finders,
pump lasers (to drive another laser), SHG's (double the frequency to
get visible light lasers), active night vision systems, WORM disk drives,...

However, IR lasers are not visible. There are visible red diode lasers,
but they are a quite recent development and therefore costly. Chances to
find them in a surplus store are small and they are much less fun then a
HeNe laser tube because the beam is very wide: 30-40 degree are typical.
So you need some good optics to make a nice beam and coherence length isn't
up there either (hence you see less interference patterns, have more trouble
with making good holograms, etc.).

Also, diode lasers are very sensitive to electrostatic discharges and are
easily destroyed. HeNe tubes are much more robust (electrically).

Finally, 7-25W lasers are downright dangerous, especially since you don't see
the beam (actually cone in this case: due to their small size, diode lasers
don't produce low divergence beams without external optics).
-- 
   --  Andreas Nowatzyk  (DC5ZV)

   Carnegie-Mellon University	     agn@unh.cs.cmu.edu
   Computer Science Department       (412) 268-3617