A while back, I spotted on Amazon something that was just too good to pass up: a 10-pack of red laser modules for, if memory serves, $2.71 including (slow) shipping. Naturally, I just had to order two.
Well, the postman just delivered a small plastic envelope containing my 20 little modules. I took one out and hooked it up to the lab power supply.
Feed it around 20mA @ 4V (it does have an internal resistor, so just connecting it across a lithium cell would be fine) and it lights up, leaking quite a bit of red light around the back of the housing while putting a nice bright vaguely-roundish red dot on the wall.
Yes, they're actual lasers, not just LEDs with lenses. The speckle pattern is a good clue.
For just over two bits per.
Now, should I suddenly develop a need for a tiny laser module (or several), I have some in my goodie box.
Added: These. Price has come down (!) slightly in the past month.
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