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Thread: Gain Medium

  1. #11
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    ... Adam (buffo) asked me to drop in for some "related crosslinking"

    You can easily bild a "visible laser setup" with higher powered blue (445nm) diodes with powers of 2W, 3,5W or 6W -- will be enough to engrave and cut cardboard, some millimeters plywood or coloured/dyed plastics, but not enough for metal.

    On the other hand - even the invisible IR lasers will create a visible (mostly white) plasma spot when engraving/cutting metal.

    What's your budget?

    I'm DIY (and proffessional/comercial too) laser-aplications since maybe 25 years, beginning with CO2-lasercutters, diode-modules and fiber-lasers -- either on CNC-setups or with XY-galvoscanners - so enough basic know-how around

    Viktor

  2. #12
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    buffo pinged me about this thread.

    i built a 60W cnc co2 laser cutter a while back. it is by no means portable or safe for the general public. the fundamentals are pretty basic, but they run on roughly 20kv, have water flowing through the tube, and the beam is invisible. plus, there's endless amounts of fiddling to keep things in alignment, clean, and level. it's absolutely a labor of love, and i don't regret it in any way. if you plan on bringing a cutter around public use, I would absolutely encourage you to go with a commercial and fda / cdrh legal system.... you do not want a lawsuit.

    having said that, i'm happy to answer any questions you might have. here's a little footage of my system in action.

    suppose you're thinkin' about a plate o' shrimp. Suddenly someone'll say, like, plate, or shrimp, or plate o' shrimp out of the blue, no explanation. No point in lookin' for one, either. It's all part of a cosmic unconciousness.

  3. #13
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    ... for CO2-lasercutters with powers below 100Watts (good for wood, acrylic/plastics and most organics) there are sealed RF-CO2-lasers, which are powered with 24 or 48 Volts, so not this problems with high votages ... and too much easier to control (or DIY drivers) and shorter in length than the glass tubes.

    A new 30Watt RF CO2-laser will cost something around USD 5k, a refurbished (refilled) with the same lifespan like a new one (3000 to 5000 hours), will cost half of this ...

    Viktor

  4. #14
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    sure.. i'd love to go with an rf tube, but that would double the cost of my machine.

    Quote Originally Posted by VDX View Post
    ... for CO2-lasercutters with powers below 100Watts (good for wood, acrylic/plastics and most organics) there are sealed RF-CO2-lasers, which are powered with 24 or 48 Volts, so not this problems with high votages ... and too much easier to control (or DIY drivers) and shorter in length than the glass tubes.

    A new 30Watt RF CO2-laser will cost something around USD 5k, a refurbished (refilled) with the same lifespan like a new one (3000 to 5000 hours), will cost half of this ...

    Viktor
    suppose you're thinkin' about a plate o' shrimp. Suddenly someone'll say, like, plate, or shrimp, or plate o' shrimp out of the blue, no explanation. No point in lookin' for one, either. It's all part of a cosmic unconciousness.

  5. #15
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    ... yes, the price is a bummer, compared to USD 300 for a glass tube with PSU :-/ ... but 10x the life-time, smaller footprint, air-cooled instead of water and much easier pulse-control is a totally different game

    For this was my question for his budget plan ...

    Viktor

  6. #16
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    absolutely. they are better in all aspects except price. i hit ebay now and then in search of a rf head to drop into my cutter.

    Quote Originally Posted by VDX View Post
    ... yes, the price is a bummer, compared to USD 300 for a glass tube with PSU :-/ ... but 10x the life-time, smaller footprint, air-cooled instead of water and much easier pulse-control is a totally different game

    For this was my question for his budget plan ...

    Viktor
    suppose you're thinkin' about a plate o' shrimp. Suddenly someone'll say, like, plate, or shrimp, or plate o' shrimp out of the blue, no explanation. No point in lookin' for one, either. It's all part of a cosmic unconciousness.

  7. #17
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    ... another interesting type are fiber-lasers - the prices are in a similar range as for the RF-CO2-lasers, but much better suited for metal (not so good for wood and organics).

    Have some at home to "play with" - either 50W to 85W as CW-types (with pulsing/modulation it stays at the same peak power), or 16Watt or 20Watt pulsed (pulse peak powers up to 10 Kilowatts!).
    They are good for marking and can be used for cutting thin sheets of metal (e.g. 0.3mm brass or 0.5mm steel) - here testing with brass:
    https://vimeo.com/214745770

    Viktor

  8. #18
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    Hi Adam,

    ... did read your post more detailed:

    Quote Originally Posted by buffo View Post
    ... In fact, VDX has been cutting metal at thicknesses similar to this using his Blu-Ray cutter.
    My "blue" laserdiode modules are based on the 445nm or 448nm diodes with 2W or 3,5W max. power, not the 405nm "Blu-Ray" diodes, which I've got until now only with max. 300mW of power (but there are some with 1W on the market too).

    The "metal cutting" I've done, was made with pulsed fiberlasers (1064nm or 1070nm) - either 20W or 60W averaged (up to some ten Kilowatts pulse peak power).

    Have some salvaged 975nm-IR-diodes with 0,1mm-fibers attached to them (from broken fiber-lasers, where they are used for pumping) - have types with 5W, 9W, 25W and 30W.
    Can focus them on a spot of 0,1mm diameter, what's enough to engrave or cut some dark plastics or solder or braze, but not enough for engraving or cutting metal - here I'll estimate minimum 40 Watts to start with engraving ... or >200 Watts for welding or cutting ...

    Viktor

  9. #19
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    Not much surprises me anymore, but I am awed by the response I've gotten here. One and all, thank you for taking the time to provide so much information and detail. It's gonna take me a while to absorb all this. Fortunately I'm doing this as a hobby; I've got the inclination to do the homework and there aren't any deadlines.

    I have a bit of familiarity with fiber optic cabling (mainly its applications in digital signalling and networking; my engineering specialization is IT). I recently wondered "what would happen if you attached a fiber optic cable to a Blu-ray laser diode?" (which I'm certain is a whole topic in of itself). That led me to "does the end-to-end length of the cable have any effect on what comes out on the far end?". These brain-wanderings have proven serendipitous; as I was skimming this thread, the phrase "fiber laser" caught my eye. On top of that, I note two things: Nd:YAG rods come in a variety of lengths and diameters, and there are a number of similarities between Nd:YAG lasers and fiber lasers.

    My googling got me as far as "fiber optic cable laser collimation lenses" when I realized just how far the rabbit hole I am: time to pop the ejection seat and ask the Lexicon! I apologize if any of these questions are "asked and answered" in previous posts on this thread; I clearly have much theory to learn and, with the way my brain is wired, having concrete answers to specific questions is of immense value to me when learning theory (Professor Feynman strikes again!).

    Defining "output" as "what happens when you point it at a piece of wood":

    1. In a fiber laser, what effect does the length of the "gain cable" have on the output?

    2. In an Nd:YAG laser, what effect does the length and diameter of the rod have on the output?

    3. Assuming a "PlayStation 3-compatible TOSLINK of average materials quality" fiber optic cable, and assuming you put the beam emitted by http://www.wickedlasers.com/arctic directly into the core of said cable, what would be the output?

    Once again, thank you all for indulging me - it is greatly appreciated.


    (Edit: definition of "output".)

  10. #20
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    ... the length of the "lasering" fiber in the fiber-laser is defined mostly due cooling, same for length and diameter with laser rods in the Nd:YAG lasers -- they can only accept a specific amount of energy per volume (length), or they change optical and mechanical properties or simply burn/evaporate away.

    Try to translate this German article, which is comparing diode vs. fiber-laser an giving some basic infos - https://www.or-laser.com/de/news/dio...e-einfuehrung/

    Biggest problem while coupling/inserting a laser beam into a fiber are reflexion losses at entry and while feeding inside - mostly entry -- this can be up to some ten percents, if not proper AR coated and not fine enough focussed beam.

    I have some fiber-coupled IR-diodes with 50 microns core diameter, but common are 105 microns (for up to 150Watt!), as it's easier to get the energy in ... or even bigger (200 or 400 microns) for super high energies in the Kilowatt range.
    Look at the images in post #39, showing the focussing of diode emitters into fibers:
    https://photonlexicon.com/forums/sho...ghlight=opened


    - and here two other threads showing some "fiber-tinkering":
    https://photonlexicon.com/forums/sho...ighlight=975nm
    https://photonlexicon.com/forums/sho...ighlight=808nm

    Viktor
    Last edited by VDX; 05-16-2018 at 22:56.

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