🚀 go-pugleaf

I once got some poorly-translated data sheets on laser diodes from
Sharp, of Japan.  These were made primarily for CD players.

What turned me off about them was that they were four-terminal devices.
They include a phototransistor.  I guess you're supposed to adjust the
power in response to the emitted light level.  They didn't include any
application notes, so I wasn't sure how I was supposed to use these things.

For all I know, just putting a battery across one of these things might
put it into a positive feedback loop, where its resistance drops to zero
and it blows itself out.  (I'm not saying that's what happens.  It's because
I didn't know how to handle these things that I was afraid to buy one.)

So my question is:  how do you use these things?  All I want to do is
build a small laser, so I can throw a red spot on a far wall.  Who makes the
most powerful device, and what does it cost?