685nm laser-in-a-box

Have I mentioned I like putting lasers in boxes instead of round hosts?

So here's my newest addition to the wavelength collection. A 685nm laser-in-a-box!

Also happens to be my first laser built from scratch, with the "module" recovered from a dead 405nm mini pen and a point to point soldered LM317 driver. The only part purchased specifically for this was the diode.

First I tested the driver on a breadboard, with a 22Ohm resistor and a pot to set the current. The 22Ohm should set it at 57mA, which is within spec of the diode. Haven't tried to push harder, at this current the diode already gets warmish and I don't have proper heatsinking.


Here it is on the box. Dropped the pot, since it is already quite low powered I won't want to set it lower anyways. Notice I didn't have a proper tool to press the diode on the (bizarre) module, so I just hot glued it in place. Probably has very poor thermal contact but works. Hardest part of the build was glueing that plastic separator for the batt compartment!


With battery and lid closed. I really like how it is transparent.


Here's it pointed at the Ophir (the paper is just to keep it centered on the sensor). As all boxes it can stand on the side and also on the "tail" (no pic of that).



It's quite stable at 30mW, despite the crappy lens of the recovered module. Have I mentioned it's also focusable? Unfortunately at that power level it isn't very useful. Not a "flashlight" and won't even light a match. Will smoke black rubber but that's it.

Here's proof that it isn't just a 650nm laser:

Three lasers through a diffraction grating. On the bottom are the main, undiffracted dots. On the top are the first order diffractions of each laser: the 30mW 685nm on top, a 650/660nm 3.5mW pointer on middle and a 4.5mW 635nm pointer on bottom.

What about the color difference? It looks very similar to the 3.5mW 650/660nm pointer in both brightness and color. That said I'm now convinced there's indeed a *very* small color difference to 650/660nm. It looks slightly more crimson, but I can only catch the difference on very diffuse and white surfaces. Here's a shot on a marble bench:

635nm on top, 650/660nm on middle, 685nm on bottom. The 685nm does *not* look slightly pinkish in real life.

That's all, folks! Hope I haven't bored you to death with this weakling

Hey, great DIY... I really love the look of "hand made" lasers. Like the traditional Altoids Tin diy!

Just noticed its a strange module. Do you know the package of the diode?

+1... :beer:

Nice color comparison shots :beer: good review

Thanks, guys!

The diode is a standard 5.6mm. I didn't have an aixiz module around so I just reused the module from a dead "mini new wish pen" 405nm. Was easy popping the dead diode out but I had to hot glue the new one on the correct position because I didn't have a proper press tool (TBH I don't think a regular press tool would work, the hole is too narrow).

The module came with a shitty plastic lens and spring, so I reused that as well. Works decently at this power level.

Extracting the diode can be done using a common, radio antenna. You can see how I did that in my Aurora SH-032 thread

link here

Anyways I have an aixiz heatsink laying around here. For a small fee you could send me the diode and I could press it correctly into an aixiz, without the module heatsinking (operating as a bare diode) it won't last long...

That's a good idea, noted!

This diode was too cheap, probably not worth even the cost of sending to you and back again I got 3 in the pack for $13, I'll see if I get at least one in a proper module. I have to get the proper tools sometime, anyways!