Build thread: 4.4W 445nm dual diode laser

Hey LPF,

I started this project a quite while ago after admiring Wannaburns 3.5W handheld for so long. Everything is starting to come together and I figured other people would like to see it come together and offer advice.

The original plan was to use two binned M140 diodes with "G" lenses through a PBS cube using a waveplate to maintain the beam orientation then to use prisms for correction. This involved a lot of expensive optics, so a lot of the power would be lost in the beam combining/correction. I also ran into issues when testing the prisms, it was difficult to align it so that the beam came out centered and perpendicular to the host.

Concept:
The plan now is to knife edge the two beams together and use cylindrical optics for the correction. Since I started this the 9mm diodes have also come out, with very good results so I changed the diodes I was going to use to two 9mm diodes. I already have the diodes, and I would test them, but my power supply has been having issues and I don't want to risk killing a 100$ diode.
I estimate that I will get about 2.5W out of each diode running them at ~2A. The losses from the mirrors will be about 5% each and the losses from the cylindrical optics has yet to be tested, I estimate about 15%. This will give me a loss of 25% on one diode, and 15% on the other. This amounts to an estimated 625mW on the lower power diode and a 375mW loss on the higher power diode, totaling 1W loss giving 4W of output. I will test the diodes and position them based on the results such that the one with the lower output will be bounced on the mirrors.

Batteries/Drivers
The power source for this all will be 3x 18650 Panasonic 3100mAh cells in a triple 18650 holder for a total of 12V. The drivers for this all will be two blitz bucks. I was originally going to use a single Flexmod P3 for the interlock and 7 second start up delay features, but it generates unnecessary heat.
Each diode will be driven independently by a blitz buck driver so that I can run them at different currents depending on how efficient each diode is.


A 3D rendering of the heat-sink and optics portion of the host, setscrews holes and threads for a cap to cover up the heatsink/optics not shown.

Edit:


:thanks: for looking.

Re: Concept: 4W corrected 445nm handheld

Id try and eliminate one of those mirrors by repositioning the diode, it will save you some
loss.. Also you may want to incorporate brass into the bench for the optics or variations
in temp will affect alignment.

It may sound odd that a few deg can make a difference, but I have seen this in mine...
A trench down the middle with a brass block filling it does wonders :beer:


I guess this means I have to go for a 3 LD when you finish this project :undecided:

Re: Concept: 4W corrected 445nm handheld

JLSE said:

Id try and eliminate one of those mirrors by repositioning the diode, it will save you some
loss.. Also you may want to incorporate brass into the bench for the optics or variations
in temp will affect alignment.

It may sound odd that a few deg can make a difference, but I have seen this in mine...
A trench down the middle with a brass block filling it does wonders :beer:


I guess this means I have to go for a 3 LD when you finish this project :undecided:

Click to expand...

Thanks for the advice! I guess I could rotate the other diode so it goes directly into the knife edge mirror.

I didn't even think of warping due to heat... Thanks! You saved me from learning that one the hard way :beer:

Re: Concept: 4W corrected 445nm handheld

What optics you intend to use ?

Re: Concept: 4W corrected 445nm handheld

DrSid said:

What optics you intend to use ?

Click to expand...

The correction optics from Dr Lava's GB.

http://laserpointerforums.com/f55/cylindrical-correction-optics-445-638-a-52925.html#post739703
http://hacylon.case.edu/ebay/laser_diode/Lenses.php

Re: Concept: 4W corrected 445nm handheld

You have them already ? I've been looking for some feedback on them. Also I heard Dr.Lava has some shipping troubles lately.

Re: Concept: 4W corrected 445nm handheld

I didn't even bother to ask Dr Lava, I just PM'd everyone from the group buy (two at a time because of LPM limits ) and asked if anyone wanted to sell theirs.

I do already have them and I will post the results soon :beer:

Re: Concept: 4W corrected 445nm handheld

That is an epic project and I can't wait to see how it turns out!

Will it be possible to achieve the same beam width and divergence of a single diode laser?

Re: Concept: 4W corrected 445nm handheld

ElectroMagneticFreak said:

That is an epic project and I can't wait to see how it turns out!

Will it be possible to achieve the same beam width and divergence of a single diode laser?

Click to expand...

Probably. It's kind of hard to test that at the moment, but once it's done I'll do the divergence calculations, it might even end up being better than a single diode 445nm laser, I am hoping to achieve a square beam.

Re: Concept: 4W corrected 445nm handheld

JLSE said:

Id try and eliminate one of those mirrors by repositioning the diode, it will save you some loss.

Click to expand...

A good mirror only loses 1-2%, doesn't it? That's less than the margin of error for virtually all power meters anyway. Is it really worth it? Additionally, it's much easier to aim a mirror than it is to aim an entire module.

Re: Concept: 4W corrected 445nm handheld

Wonder if a pbs might be more beneficial? You'll end up with a + shaped beam but the laser will be much more intense (by an magnitude of 100'w of milliwatts) at the centre of that + versus a knife edged || style beam. Adding a cut down 1/2 wave plate would further increase the power - the beam will be the same size as a single corrected diode, with roughly the same power as a dually

You wave plate the right diode, and bounce it off the mirror and replace the left mirror with the pbs. If you are happy with the + configuration, omit the wave plate.

Re: Concept: 4W corrected 445nm handheld

Perhaps, wave plates are expensive though I'll see how it goes once I have the host made.

Re: Concept: 4W corrected 445nm handheld

I guess the point of correction is to improve divergence of fast axis. + beam cannot be corrected this way, and it wont be same. It will diverge badly in two directions, instead of one, compared to single uncorrected diode.

Re: Concept: 4W corrected 445nm handheld

Cyparagon said:

A good mirror only loses 1-2%, doesn't it? That's less than the margin of error for virtually all power meters anyway. Is it really worth it? Additionally, it's much easier to aim a mirror than it is to aim an entire module.

Click to expand...

Well loss depends on the mirror's used and the ease of aligning only one
opposed to 2. Also drilling out that 2nd hole off center lengthwise allows more room for error.

That 2nd hole will most likely be done on a mill, and the longer it is, the harder it
becomes to keep on dead center. You can use the mirror to correct angle, but
if that hole is slightly elevated, it works against the idea of parallel beams..

I have tried many configurations and found the best results as described
with the modules mounted in an L shape.

Aside from that, it also cuts down the overall diameter of the head, My duals
are 25mm O/D vs 2 modules side by side @ 35mm or so.

The working area for combining alone is 25mmx25mm, total length with the same
cylindrical optics is 53mm. Keep in mind I minimize lengths of the lens nuts, and
modules to get the dimensions right down.


@ARG,

Be sure to account for all measurements like module depth, protrusion of the lens
nut etc. There is going to be some things I cant think of as I havent tried this
with the 9mm diodes, and they require a longer module etc.

Best bet is mock this up, and focus on your collimators and positioning. A small
error will cost you much time especially if you are having this made for you.
If the machining is in house, its not too bad, you can change things on the fly.
Otherwise its extra wait time and $.

Re: Concept: 4W corrected 445nm handheld

JLSE said:

@ARG,

Be sure to account for all measurements like module depth, protrusion of the lens
nut etc. There is going to be some things I cant think of as I havent tried this
with the 9mm diodes, and they require a longer module etc.

Best bet is mock this up, and focus on your collimators and positioning. A small
error will cost you much time especially if you are having this made for you.
If the machining is in house, its not too bad, you can change things on the fly.
Otherwise its extra wait time and $.

Click to expand...

Yeah, I counted on inaccuracy's in my measurements so I added 5mm onto most area's so that space wont be a problem. It only made it 15mm longer, so why not.

Machining is being done by a company and I'm going to get a couple of different styles made. I wish I had the tools to make this myself :undecided: Edit: Machining was done by Ehgemus in the end.

Re: Concept: 4W corrected 445nm handheld

@ arglaser

Why are you choosing M-140's? You couls also use 2x binned 9mm 445? that would be insane!

good luck on your build really interested in the progress of this build!

greetings,,