Building A CO2 Laser In A Hardware Store

Over on the Projects site, [ThunderSqueak] is pushing the bounds of what anyone would call reasonable and is building a CO2 laser from parts that can be found in any home improvement store.

Despite being able to cut wood, paper, and a bunch of other everyday materials, a carbon dioxide laser is actually surprisingly simple. All you need to do is fill a tube with CO2, put some mirrors and lenses on each end, and run an electric current through the gas. In practice, though, there’s a lot of extra bits and bobs required for a working laser.

[ThunderSqueak] will need some sort of cooling for his laser, and for that he’s constructed a watercooling jacket out of 2″ PVC. In the end caps, a pair of brass pipe fittings are JB Welded in place, allowing a place for the mirror assembly and lenses.

The mirror mounts are the key component of this build, but the construction method is surprisingly simple. [ThunderSqueak] is using a few brass barbed hose fittings, with washers stuck on one end. The washers are drilled to accept a trio of bolts that will allow the mirrors to be perfectly parallel; anything less and the CO2 won’t lase.

The build isn’t complete yet, but having already built a few lasers, there’s little doubt [ThunderSqueak] will be able to pull this one off as well.


67 thoughts on “Building A CO2 Laser In A Hardware Store

    1. I am very admired for your interest, but the machine inside the CO2 laser is not only CO2, but also the parallelism requirement for the lens installation is very high, you have to calculate the length of the cavity and the curvature of the mirror, as well as the output. The transmittance of the window.

    1. Length of the tube (and thus power) is limited by the power supply and by the cooling…this can be cheated by using multiple tubes at the expense of a more fiddly optics assembly ;-)

  1. “Fill the tube with CO2” is kind of understating it. You need to get a mix of CO2, nitrogen, and helium. And while CO2 lasers are famously tolerant when it comes to the final gas mix, the whole shebang has to be maintained at low pressure and generally babied along to begin lasing.

      1. Your own link says “Forget about lasing breath without helium.”
        Using exhaled breath you need helium. Using pure CO2 doesn’t work since you don’t have nitrogen. Doing any of these still requires pulling a vacuum. Getting useable energy out of it requires helium, CO2, nitrogen, the pump, and a decent length.

        “If you know what you’re doing” it’s not that hard. But we’re not talking about people who know all the tricks, are we? I said “Filling the tube with CO2 is understating things.”

    1. Also the helium that is found in department stores is supposedly anything but pure. It is usually diluted with air. I have not hooked a bottle to my mass spec to look, I should someday.

      1. Still, that’d provide the nitrogen, you’d just need a way to suck the oxygen out. Would it be possible to burn some pure charcoal (ie not bbq stuff) in this gas, to leave just He, N, and CO2? Maybe graphite even? Just guessing.

        Failing that I dunno, diving suppliers or maybe a science supplier?

        1. A nitrogen laser is very dangerous produces some bad ass UV – as in skin cancer levels. Can anyone explain why the He,CO2,N2 mixture is needed and what the correct proportions are ? Curious more than anything else.

          1. I am going off memory and I might be out of order here but if I remember right Nitrogen gets ionized, transfers it charge to the co2. The charge from the CO2 is transferred helium, when this happens an photon is emitted and then then the helium looses it charge when it hits a wall.

            You might want to look it up, it has been a while even though I work on the CO2 lasers at work, in fact I am changing cavity optics on the 1600w Mitsubishi at work tomorrow.

          2. From my laser design engineering school classes, the trouble is the excitation bands don’t line up. Let’s say you want wavelength X out of your laser. However, you’re pumping the gain medium with wavelength F from a xenon flash bulb source. CO2 doesn’t excite in the F band. So, you excite another gas which gets excited at F and releases photons at G. Eventually, you get a F -> G -> X -> Y cascade setup. The whole thing is a lot more complex than that as you’ll face other troubles like your CO2 wants to break down, but other gases will buffer it better, stabilizing the whole deal. There are problems with spacial, temporal, and spectral stability and homogeneity of the beam, but it’s been a while since those classes, so I can’t elaborate.

          3. Despite the name, CO2 is only the third gas in the CO2 laser cocktail. For a 100W tube (about 1.5m long), that’s roughly 75% He, 15% N, and 10% CO2. The ratio varies depending on the size and design of the laser. Other trace gases are added as well including Ar and water vapor. A common problem is the that CO2 degenerates into CO, and that messes up the ratio. So the trace gases (and tube structure) are designed to efficiently reconstitute the CO2.

            In use, Nitrogen molecules are excited (typically thru an electrical discharge, but also RF excitation is common). One of the vibrational modes of the CO2 molecule is close to the excited N2 energy level and the Nitrogen gives up its energy to the CO2. When the CO2 decays from this excited state, the desired 10.6um photons stimulate other excited CO2 molecules to decay as well (this is the “stimulated emission” that is part of the LASER name). [9.6um is another common CO2 transition, and some lasers are designed for that wavelength instead.]

            CO2 lasers are very efficient, but not *that* efficient. For comparison, HeNe lasers are less than 1% efficient, while CO2 lasers are typically 15~20% efficient. For a 100W laser tube, you pump it with 600W of electrical energy, to get 100W of 10.6um photons. The remaining 500W is wasted heat, and many lasers use a water shroud integral to the tube, to dissipate the wasted heat. The He gas that is part of the mixture is used to transfer the heat out of the gas and to the tube walls, where the water jacket carries away the heat.

        2. That would also produce NOx, which decompose in the laser into O2 and N2…

          A more reliable way is to stuff a pyrex tube with iron chips/shavings and pass the gas mix through while heating the tube to >400°C, it will also take care of some of the moisture ;-)

      1. You can get it from Airgas too, I think I paid ~$80 for a 40 cuft bottle when I built mine. We get premix for the Mitsubishi laser at work and the Bystronic we have mixes it’s own from three ultra high purity bottles.

  2. Only CO2 LASER I ever got to mess with was a 150W baby in an engraving machine. It didn’t use electric current per se – but RF energy to excite that tube. Full water jacket and separate cooling system. I know because someone forgot to turn on the cooler before they started the job. The LASER ate itself. Ha ha ha ha!

  3. I’m very doubtful that it will ever work. I did repair 1,5KW Co2 Lasers. The greatest problem will be to get it hermitically sealed (you need a vacuum pump and a gauge), it will be easier if you keep the pump running and fill the gases constantly, then the problem of high voltage arcs (1mm/KV) and pre-ionization (10mm/KV).
    I don’t say it’s impossible, but you should get higher standards.

    Anyway here the most amazing girl, who did build herself 2 lasers and lot more:

    Sorry it’s in German, but it’s so interesting and you could learn a lot from it.

    1. People have good success with epoxy for sealing, and a fridge compressor easily does 100 torr. Since the DIY tubes are seldom sealed you can dump monstrous amounts of power into the gas, breaking down the CO2 into CO but getting decent a rather hot beam out of them.

      Cooling and recirculating the gas is hard, since the plumbing becomes monumentally more complex. You can however probably do enough with copper break lines and solder.

  4. “is pushing the bounds of what anyone would call reasonable”
    I built one in high school… 20 years ago…

    Scientific American had how to build one in their Amateur Scientist column in the late 60’s or 70’s. Then there was the plans in the “Build your laser, phaser, ion-ray gun” book.

    Its just not economical to build one now. With cheap chinese 40w tubes being just over $100 it is pointless to build a flowing gas CO2 that will end up costing you way more.

    1. Hm, what was the phaser? I suppose the ion-ray was just an ioniser? HV source to spray electrons? Even with something to focus it, I’m not sure how much use an electron beam would be in air. Maybe you could give stuff static charges over the small distance before the beam’s dissipated in the air.

      Still, what an awesome-sounding book. And they wonder why not as many kids go into science and engineering these days. Cancelling the manned space program hasn’t helped much either. What would Captain Kirk do with an Arduino?

      1. …Well I did just drill a hole through the panel of an old CRT monitor, keeping everything else intact. I could find out what it does in air but it would probably arc and melt the filament in seconds. It’ll turn into a Bell jar with integrated electron beam vapor deposition for making GaAs optics for my own CO2 laser.

        1. Wow! You’re going to fire electrons as some gallium arsenide and let it deposit to make crystals? That’s a brilliant thing to do with an old monitor. I hope HaD will run something on it, that’s a real hack. From 1930s vacuum-tube electron-beam technology to the sort of stuff that’s cutting-edge in microchip production.

          1. The research I read says it’s possible… so if I can take the front panel off a big CRT and have it hold together when evacuating it again I can use the original electronics to create a beam. On my first try just today with a small CRT I didn’t remove the implosion band before applying heat, so the tube cracked. I figured I’d need the band for structural purposes so I tried removing it through heat expansion. Well, I got some high quality glass to sinter out of the attempt, I suppose. I could also see what the electron gun does in air now…
            My project is located here:

  5. as there are no DUMB questions, here’s a dumb question…

    If he needs to excite the tube to get the atoms to jump state, how do you do that while cooling the tube with water? High Voltage plus water normally equals steam or worse…..the writeup didn’t say…

    1. Pure water is actually an insulator. That being said, pure water is also very difficult to find seeing as it can dissolve many many different chemicals and compounds.

      The water jacket sourrounds the inner tube where the high voltage and gas resides. The HV doesn’t come in contact with the water at all. Even if it did, you’d just get a bit of arcing, voltage alone won’t make water heat up one bit, that’s all about the current and to make steam you’d need a LOT of it, so much that you’d be splitting it into hydrogen and oxygen first.

      1. Older high-power YAG systems (flash-lamp pumped) typically flow the cooling water directly over the flash lamp (or at least in contact with both ends of the tube, electrodes and all). To prevent a short, the cooling system uses a de-ionizing filter to make sure the water has as little conductivity as possible.

  6. Something from the early days of the Buildlog laser cutter forums was that folks were cutting circular sections out of old hard drive platters and using these for mirrors in their cutters instead of the ZnSe mirrors one often uses. I’m not sure what you’d do for the half silvered mirror, though.

    1. Basically the same thing, except you drill a small hole in the middle, and over that place (seal) a polished piece of rock salt “window”. Generally, you attach the window using silicone or something similar (because you will need to remove it once it fogs from soaking up moisture).

  7. Please be careful. I repair high powered (1KW – 8KW) industrial lasers for a living. They will mess you up before you know what hit you.
    Commercial Co2 lasers are typically energized by huge RF generators, which you cannot buy at the hardware store. I think.
    Deionized water: fresh steam distilled water typically has a conductivity around 2uS/cm, which is very low. It’s $1/gallon. You have to change it frequently or run it through a deionizing filter to keep it neutral.

  8. “All you need to do is fill a tube with CO2, put some mirrors and lenses on each end, and run an electric current through the gas. In practice, though, there’s a lot of extra bits and bobs required for a working laser.”


  9. Yikes O.o;; I didn’t expect this to be put up here as I built it a while ago and just decided to put up the information on so others could take a look at it. I have other pictures and information of it in action and pics of the tube while it is active that I still need to put up. Also, pronoun above is wrong, should be she ^^;;

    The laser gas is composed of helium, co2, and nitrogen. I have several set of optics for it as well currently. The DIY ones do work but are no where as efficient as using proper ZnSe optics or Ge lenses and mirrors.

    Lately my interest is on my other project, a base 3 (ternary) computer built from scratch. I plan on putting up the build log at–Ternary-Computer-from-scratch


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