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7W 450 nm handheld build

RedCowboy

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I have built several, it's not prohibitively difficult as long as you are patient, you just have to line everything up by aligning on a distant point, I use a board @ 15 feet and it works well, my point at infinity looks amazing and lighting paper/cardboard @ 50 feet is no problem and even without the beam expander the corrected beam looks much better, much more the way a laser beam should.......this unit is meant to be a 2 x 44 build, that's the reason there's so much empty space, but I was testing the mount for heat transfer so I didn't take a lot of build pics or post about it but here's a corrected 5W 7A75 I did a while back


SANY5058.JPGSANY5047.JPG

p.s. The idea was to PBS combine 2 x 44 and I have a wave plate to rotate the 2nd beam then correct the combined beam with a 6X C-lens pair but I think I want to correct each beam 1st via. 6X c-lens pairs then PBS combine the corrected beams and it's all going to align perfectly with a beam expander mounted at the output. Do you think that would be the better way to go ( correcting each beam 1st ) it would reduce the energy density at the PBS as the beams would be expanded to their final size, if I tried to PBS combine straight out of my G2's the beams would still be pretty small/tight at the cube which could be a problem, I should test one but they were expensive and hard to get cubes that are able to take 2 x 44's so I think I want to correct each beam 1st, also I like to correct the beam as soon as possible as the fast axis divergence is so aggressive.
 
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Buffo

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Nice work, Cowboy!

Clearly you have your own mill. That certainly helps when building custom units like these. Although I have to admit that the very large head assembly shown in your pictures is a bit at odds with the whole "handheld" motif! :) It makes the pointer look like a mace! But yeah, if you want to cram a pair of diodes in there, plus secondary correction optics, plus a waveplate and PBS - well, you're going to need plenty of space, and all that extra mass on the front is going to totally unbalance the thing.

One suggestion to make it more compact would be to use stronger lenses (shorter focal length). I've also seen solutions that use 3 lenses, as it seems that it's easier to find very short focal length converging cylindrical lenses compared to diverging cylindrical lenses. So you end up with two diverging lenses (one after the other) and then one big converging lens. But I've never actually attempted a 3-lens build myself. (I have assembled modules with anamorphic prisms too, but they need even more space than a pair of cylindricals.)

Regarding the decision to correct before or after the PBS cube, that's tricky. If you can't get accurate data from the manufacturer regarding what sort of power density the optical coating can handle, then it may be wise to do the correction before the cube even though this adds cost and complexity. It would also give you the best beam quality though, as you mentioned.

Truthfully, if this were my project I probably would do the correction first, before the cube. But I'd also look into different optics to try to reduce the path length. I've pulled the lids on several commercial modules that use cylindricals for fast-axis correction of multimode blues and greens and I've seen 3-lens solutions that only took up 12 mm of linear space. Granted, I don't know what diodes they were using, but it had to be something in the 2-3 watt range for each diode.

Addressing the elephant in the room for a moment: what the heck are you going to do with a 14 watt hand-held? :oops:

Adam
 

RedCowboy

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I like a long duty cycle but I have built both big and small.

I don't have a lathe yet but I do a lot without it, what I can't make I have made however you can do a lot with a drill press and slide vise.

My optics are affordable which is a bigger factor than saving a little bit of space ATM not that there's all that much to trim.

I am big on laser safety, everyone remember to wear those attenuation glasses..........7W or 14W is not really a big difference as far as the need to lase safely but I would love to have 1400W in a hand held even if it's only a wand and a backpack full of laser, batteries and a radiator. :p as for what for.....for lasing enjoyment. :cool: Safely of course.

 
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Buffo

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Hmmmm... Drill press + slide vise as a surrogate for a lathe? Now that's what I call adaptation! :)

I've actually considered buying a mini-mill a few times in the past, but I've always decided against it at the last minute. To be fair I probably don't have the time to learn everything I would need to learn in order to use one properly anyway. Plus I can totally see myself losing a finger or two due to my own stupidity.

Regarding safety, you are correct of course. Once you are well into Class IV territory there isn't a huge difference between 7 watts and 14 watts. Both are more than capable of causing serious injury and starting fires. But the reptilian part of my brain is still intrigued by the idea of 14 watts in a hand-held package. (Admit it: we all want a light saber!)

I remember one of the UK guys built a portable CO2 laser about 8 years ago that had a backpack to house the batteries and the PSU. I think it only made 10 or 12 watts, but given that the beam was invisible it was rather terrifying. The head was about 20 inches long so it was more like a laser rifle than a pointer, but even so it was a cool concept. But with modern multi-mode diodes it's totally feasible to build a hand-held *visible* laser in the same power range - no backpack required. (Crazy to think how far the technology has come in such a short time...)

Adam
 

RedCowboy

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Near IR frightens me a lot more than the 10K range of co2 but a lot of the 2nd hand fiber stuff should be in the 1550nm " eye safe " range IINM so that will be good......Safety 1st as always.

I would not buy a mini mill unless a fantastic bargain, look for a good pre owned full size unit, that's my 2 cents anyway.
 
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Buffo

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I don't have space for a full-size mill. Truthfully even a mini-mill would be something I'd have to drag out and set up in the driveway on a temporary basis when I wanted to use it. But it's just not in the cards right now - too many other things competing for my time!

Maybe when I retire I'll have myself a workshop in the back yard that I can fill with tools... Sigh.

My biggest concern with CO2 is the fact that the beam is invisible. At least with near IR you can use a digital camera to "remote-view" the beam. With 10,640 nm you go looking for the beam with a toothpick... (Much like you go looking for a superheated steam leak with a broomstick!)

Adam
 

RedCowboy

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You could use a beam combiner to add a visible beam to your invisible beam like they do in cnc applications.

 

Buffo

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RedCowboy said:
You could use a beam combiner to add a visible beam to your invisible beam like they do in cnc applications.
That's a smart idea. I think if I ever did build my own laser cutter I'd want to incorporate some sort of visible steering / aiming beam.

Adam
 




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