I've wanted to build a TEA laser for a while now, and I've finally gotten the parts and the time. Here is the building process along with everything else useful I've found for building your own laser.
First, the necessary disclaimer:
I am not responsible for you, or anything you do. If you hurt yourself I may offer you condolences, but please don't try to sue me for anything.
If you follow the safety advice given and use common sense, you should be fine.
Also, I am obviously not the first person to come up with this idea. The sources I've used the most are:
Nyle Steiner's pages (http://www.sparkbangbuzz.com/tealaser/tealaser7.htm)
The Joss Research Institute (http://www.jossresearch.org/lasers/),
Sam's Laser FAQ (http://www.repairfaq.org/sam/lasercn2.htm),
The Professor's Homebuilt Lasers website (http://www.repairfaq.org/sam/lasercn2.htm), and
Before following this instrucable, it would probably be a good idea to look at some of these excellent resources.
Step 1: Before you start...
What is a TEA laser?
In short, TEA stands for Transversely Exited Atmospheric pressure laser. While a true nitrogen TEA laser uses a nearly pure nitrogen environment at atmospheric pressure as a lasing medium, the laser I built uses plain old air which has enough nitrogen in it to lase. A TEA laser works by using high-voltage coronal discharge to excite nitrogen in the channel between the electrodes to the point at which it lases. For more details, a good explanation can be found here: http://220.127.116.11/people/mcsele/lasers/Mechanism.htm (The Professor's Homebuilt Lasers Site).
Why build a TEA laser?
Other than the self-satisfaction of having built a laser, there are a handful of ways to motivate yourself. For one, building this laser can acquaint you with skills that are useful in other parts of life. Doing projects like this one forces you to think in a creative way and learn to solve different problems. Even learning to work safely with high voltage electricity can be a stepping stone to other more interesting projects.
This particular type of laser can be built with stuff you have lying around at home, and it doesn't require special tools or skills to build. The only part that was tricky to get was the power supply, which I'll cover in a subsequent step.
These are all the questions that my tired brain could come up with. Feel free to submit your own and I will try my best to answer them.
Step 2: Safety!
-- Despite its simplicity, this laser could potentially be dangerous. Even though it probably won't be capable of starting a fire (unless something gets in the way of the spark gap), the peak power can be significantly more than that of a red laser pointer. The output wavelength is around 337 nm (ultraviolet) which means that you should take precautions to avoid overexposing yourself to UV radiation. As with all lasers, letting the beam get anywhere near your eyes is a very bad idea. Safety glasses are a must when working with high voltage, and for this project UV blocking welding goggles might be even better.
-- This project deals with high voltage. That means that there are multiple opportunities to zap yourself (perhaps even lethally) if you are not careful. Before adjusting something, always unplug everything and discharge any capacitors. If you have a weak heart or you have a pacemaker, be super careful or consider skipping this project. Make sure to insulate everything properly and practice common sense. As an extra barrier, use a pair of rubber gloves.
-- The spark gaps in this project could cause interference that might screw up electronics nearby, and the high-voltage power supply could also damage stuff plugged into the same circuit. Consider running the laser on its own outlet circuit away from anything that you don't want to fry. You might also want to remove cell phone-like devices from your pockets, just in case.
-- Ventilation is a good idea. The spark gaps produce lots of ozone that you really don't want to inhale. Plus, I find that fresh air always makes me think better.
Step 3: Tools
– Scissors. These are useful for cutting foil, paper, plastic sheet, and wire.
– A permanent marker. For marking out measurements. I personally like to use a sharpy.
– A ruler or measuring tape. For making the measurements.
– Tape. This keeps everything together.
– Sandpaper or a file. This is essential for smoothing the electrode rails.
– Various tools also help a lot; a pair of needle nose pliers is incredibly useful.
Step 4: Safety Supplies
– Thick rubber/nitrile gloves. I got zapped once. Getting zapped hurts. A lot. Now I wear these.
– Safety goggles. I haven't lost an eye yet, and these have certainly prevented potential lose-an-eye situations. They also filter out a bit of UV, which helps to prevent welder's eye.
– Screwdriver. This is handy for discharging the capacitor when you are about to adjust stuff. Use it by placing the metal part of the screwdriver across the spark gap, or in any other way that connects the top and bottom plates of the laser.
– Power strip. I used this to safely turn the laser/power supply on and off. The power button on my supply was awfully close to some other parts that floated at high voltage, so I decided to use this as a switch. The strip also has a fuse and circuit breaker in it that can help to prevent all kinds of electrical accidents.
– Fire extinguisher. Just a good idea in any experimental situation, especially those that work with electricity or fire.
Step 5: Supplies
– A high voltage power supply. Preferably DC (although AC will work if you can rectify it). This needs to be able to charge the capacitor plates up to at least 4 Kv. I used the insides from an old air ionizer, but many of the hv supplies featured on this site will work too. I've even read about a guy that used a Wimhurst machine to power his laser.
– A solid, insulated piece of something flat to build your laser on. Wood works, but glass or fiberglass would be better. I built mine on a wooden desk, which probably wasn't the best idea. The dimensions of the base should be big enough to leave space around the circuit, depending on how big you make your laser.
– Lots of aluminum foil. These will become your capacitor plates. Regular kitchen foil works fine. Thinner stuff works better but is harder to cut and tape without tearing.
– Plastic sheeting. This will become the dielectric of the capacitor. Anything thin and very insulating should work. I've heard of transparency sheets, Mylar, political signs, “For Sale” signs, and documents sheet covers used for this purpose. I used Mylar here.
– Thick copper wire or a resistor. This is used as a DC path across the top plates. Either works; the wire can be made into an inductor, or the resister can be taped directly onto the setup. However, I find that the wire tends to be better because the resistor heats up after a while.
– Angle aluminum (1/8" thick) or something else conductive with an even, straight edge. This becomes the rail electrodes that run parallel to the discharge channel. You will need 2 equal lengths for each electrode. My electrodes were 10 inches long. Make sure you sand out any burrs on the edges, and file or sand corners until they are rounded (see picture).
– A spark gap assembly. This functions as a high voltage switch. The design is limited by your creativity. I used US coins; 2 quarters and 2 pennies worked just fine. If you decide to use a different method, it's would be a good idea to make the gap adjustable.
– Something fluorescent. This will be the target of the laser. Since the beam is invisible to the human eye, something that will fluoresce under UV is necessary to convert the beam into visible light. I used a pink post-it note, although even regular white printer paper will work.
– Rocks. These are used as weights to hold stuff down to insure good connections. Fishing weights and other dense objects work too, but rocks are easier to find.
Step 6: Planning
I've seen designs as small as a CD and as long as a whole room. The dimensions of the laser depend strongly on how long your electrodes are. The laser isn't horribly picky; I made my electrodes 10 inches long and then estimated the rest of the measurements from there. If you decide to wing it too, you should have no problem if the capacitor to electrode size ratio stays roughly the same.
If you want to build yours exactly like mine, here are the numbers:
Electrodes (angle aluminum) -- 10 inches each
Bottom capacitor plate -- 12" by 12"
Top capacitor plates -- 10" by 5" each
Dielectric -- 17.5" by 11.5"
If you decide to experiment and find a size that works even better, I'd love hear what you've found.
Step 7: Construction
Measure out your electrodes (the angle aluminum) and cut them if they're not already the right length. Try to avoid bending or denting the aluminum as this could lead to poor electrical connections later.
Step 8: Making the capacitor
2. Tape down the dielectric on top of the bottom capacitor plate as shown. Let the dielectric completely cover 2 sides of the bottom capacitor plate (with a margin to prevent arcing) and leave one side of the plate exposed. This bare area gives you a place to attach the spark gap. On the remaining side, leave a tiny lip of foil uncovered to give you a place to attach your power supply. Alternately, you could cover 3 sides and clip your power on the same side as the spark gap.
3. Lay down the two top capacitor plates as shown (use tape if needed). Leave approx. a 1-2 mm gap between the two top plates.
Your capacitor is now finished. Check for creases or air spaces and try to even them out. The closer the foil is to the plastic, the better.
Step 9: Making the DC path
For those using a resistor: You're done! Yay!
Both methods work equally well at forming a DC path that resists changes in current.
Step 10: Assembly - Putting it all together!
1.Tape your inductor or resistor down, being careful not to damage the foil.
2. Put your electrodes on the top capacitor plates. Leave about a 1.5 mm space between the two for starters (You'll probably have to adjust this later). The photos show what spacing worked for me, but there's a good chance your spacing will be slightly different.
3. Put down the spark gap. Leave a 3 mm space to start, but like the electrodes you'll probably have to adjust this. Once again, the pictures show what worked for me, but you'll need to experiment.
4. Put weights on the parts that are just sitting on the laser (ie. the electrodes). This will help to maintain good contact and prevent nasty arcs from forming. I used an industrial relay and a few rocks that I had lying around, but of course anything weighty will work.
5. Making sure that your power source is unplugged, clip/tape/attach the leads from your power supply to the laser as shown. You might want to put some weights here as well.
6. Test your connections with a multimeter (if you have one). It prevents lots of trouble later.
Step 11: Throwing the switch
Now would be the time to put your safety stuff on. Gloves are a must if you want to adjust gap distances without long pauses in between. To get an idea of what you should be seeing, watch the video. Sorry for the horrendously cruddy pictures; I lifted them from a video since I haven't taken any picture of the laser in complete darkness. Check here later for more pictures!
EDIT: More pictures coming soon, along with instructions for building this laser with a neon sign transformer or OBIT!
Step 12: WHY DOESN'T IT WORK!?!?!
Here are some tips to help you adjust your laser.
If you see bright sparks at one end of the laser: Move the rails on that side farther apart, or file/sand the rails to get rid of dents/burrs.
If you see bright sparks along the laser, but it doesn't lase: Move the rails farther apart equally, or reduce the length of your rails. I had this problem when my rails were 15 inches long.
If you see bright skinny arcs across the rails: Move the rails closer together.
If you hear a large CRACK and you get no more pulses: There's a good chance you've put a hole in your dielectric. If it happens again after changing the sheet, try reducing the spark gap distance or increasing the thickness of the sheet.
If everything seems right but you get no laser action: Try changing the spark gap distance.
If you are frustrated out of your mind: Take a break! I took a one year break on this project after failing at it for a while. Hopefully these tips will help you avoid excessive frustration.
If you have any questions, or you're pleased with your success, post it!
Also, if you enjoyed this instructable, please vote for it! I've entered it into the Make it Glow and Mad Science contests.