Simple Homemade TEA Laser (2007) | Hacker News Reader

Simple Homemade TEA Laser (2007)

sparkbangbuzz.com

76 pointshamilyon235 comments

Open articleView on HN

(2007)

This is really clever! But it looks incredibly dangerous and probably emits an enormous amount of RF noise.

The article never says what "TEA" stands for:

https://en.wikipedia.org/wiki/TEA_laser

Tranversely Excited Atmospheric

Thanks for looking it up!

Since I am more familiar with rockets than with lasers, my first association with 'TEA' was 'triethylaluminum' [0] which can be used to ignite rocket engines. See also [1].

Now that we know what to look for, it does state that but it is a few paragraphs (too far) into the text:

If I understand it right, TEA stands for Transverse Excitation at Atmospheric pressure.

Writing a name out in full when using it for the first time and denoting the abbreviation that will be used further in the text might be a good idea in general.

[0] https://en.wikipedia.org/wiki/Triethylaluminium

[1] https://en.wikipedia.org/wiki/Triethylborane#Rocket

Triethylaluminum was also my first thought, so my initial reaction was "wait, you're putting what in a homemade project?"

Asking for a friend, would such a thing disrupt the connection between his neighbor's phone and said neighbor's Bluetooth speaker when he puts it next to his fence in the garden?

A spark gap generator would probably work better for that, but jamming is illegal.

Yeah I told that friend, but he feels that constantly providing background music for your neighbor's lives should also be illegal. He's looking for a more secluded house as well.

> constantly providing background music for your neighbor's lives should also be illegal

In most areas, it is often illegal, violates an ordinance, or is considered a tort.

I think this is a spark gap device. That's how it pumps the atoms in the air. Of course it's a pretty complicated way to make a spark.

"It's my arc-welder, officer."

Could you reach over / through the fence and hit the bluetooth connection button? You could probably change the volume, music, or play something offensive then. When they take it back indoors of course.

Years ago an engineer friend of mine had an upstairs neighbor who would play the same radio station at high volumes for long periods of the day, often well into the wee hours. Pleas for change had no effect.

So my friend bought and built an FM transmitter kit. He put it in his apartment in the closest spot to the guy's stereo. And then he broadcast beautiful silence on that radio station's frequency. The neighbor tried other stations for a while, but it just wasn't the same.

I wonder if a Bluetooth version of that is possible.

Uh, no. Not legally, at least.

My friend's approach wasn't legal either, so I was more asking about the technical possibility. I know Bluetooth is supposed to be more secure, but I have to wonder if random consumer electronics gear like a speaker really takes that seriously.

In a past life I had borderline crazy downstairs neighbours. They would usually wake us up by screaming at one another but on this particular occasion the radio was blasting at a ridiculous level. I actually don't think they home and perhaps it was an alarm set on the radio which had turned it on.

Thankfully after about 30 minutes of my flatmate and I getting really pissed off (it was like in the same room loud, not just a minor annoyance) I remembered that I had an old car FM transmitter for an MP3 player, after borrowing the batteries from the TV remote, cycling through the stations I was overjoyed to discover that one of the stations was close enough to the radio frequency to blot out the station it was tuned to. The reason I think they weren't home is I turned it on and off a few times but they didn't attempt to turn the radio to another channel or anything like that. I went to sleep with it on.

Technically the FM transmitter was legal at that point but using it to deliberately block someone else's radio is almost definitely illegal.

LOL. Your "friend" might be better off with a bluetooth jammer.

Probably less noisy than a car engine with traditional ignition coil. Not to mention all the PCs with glass cases.

Oh, yes indeed. And to properly shield it costs an order of magnitude more than the laser itself.

I always get really nervous every time I see the words "homemade" and "laser" in the same sentence.

I had to take a laser safety workshop in college and the stories of accidental blindings still haunt me. Those were from people who worked with lasers for a living, so god knows what people messing around with them in their garage can do.

A very cool project, but this author is much to blase about safety IMHO. UV lasers can blind you -- or, even more to the point, other people -- in an instant if you aren't careful. And they can do so across long distances. You should treat them with the same respect and caution that you would a firearm.

Here’s how to read this post.

“Any atmospheric pressure linear spark with a field greater than about 10kV/cm will show stimulated emission from nitrogen.”

This type of laser design is a well-known curiosity. It is not useful or reliable, and always winds up on a shelf somewhere, or in the trash.

I'm really happy it was posted here, since I've never heard of this effect. Do you have some further reading on the "not useful or reliable" aspect? This site, for example, lists multiple applications for them: http://technology.niagarac.on.ca/people/mcsele/lasers/Lasers...

It's especially interesting to me because (as the article points out), it doesn't require any really exotic equipment or skills to build one. I'm a little surprised no one built one long before helium-neon lasers.

If you are more of a video person, here is 5 minute video from styropyro of him explaining and building one: https://www.youtube.com/watch?v=1psxE4NlECQ

I found his videos just yesterday! I was watching a video about an extremely high powered laser he ended up burning stuff with, and was incredibly tempted to get my hands on one till he noted how they try to keep that stuff away from hobbyists lol.

It's not that hard to get ahold of reasonably high-powered lasers. IIRC, one of the ones he used was ordered direct from China, sold as a tattoo remover.

If you decide to experiment with them, please be very careful, and buy proper eye protection from a reputable supplier. There are a lot of garbage goggles out there that don't actually filter out the parts of the spectrum that they claim to. I've seen this myself with some alleged UV goggles that were the same shade of green as my actual UV goggles, but didn't filter UV light. IIRC, in the tattoo remover video, he finds the same thing with the useless "safety" goggles that that laser included.

If you have proper laser safety goggles for the type of beam you're working with, you probably won't be able to see the beam, which takes some of the fun out of it. Years ago, I saw a video of a folded-optic welding helmet that put HDR imagery on displays inside the helmet, so the eyes weren't even exposed. That would be an ideal approach for lasers, IMO, but I can't even find the video now, let alone DIY plans or an inexpensive commercial product.

It's the 21st century, but you still can't get the replacement eyes that 80s cyberpunk novels promised us. It's very easy to lose some or all of one's sight when experimenting with lasers. Back around 2010, I was about 3/4 of the way through building a laser pistol out of a DVD writer diode and some custom electronics when I realized that even in the best case scenario, it wasn't worth risking my eyesight, so I abandoned it before going from the breadboard phase to the "fits into a pistol form factor" version.

Very cool. Reminds me of the times in middle/high school when I used to hunt down computer repair shops and scavenge old or spoilt dvd/cd drives to build lasers. The diodes harvested from drives that could write to disks were powerful enough to burn through black tape and even light matches! All you needed was an LM317T voltage regulator and a housing for the diode if my memory serves my correctly. Fun times, as long as you stayed safe :)

Death Ray Lasers are what we called those in high school. They were fascinating projects because they managed to bring together the computer geeks and the gear heads in shop class.

Because everybody likes setting things on fire with lasers!

TEA laser is a new term for me. It resembles the Nitrogen UV laser I have wanted to build since I was a teenager and found the article in Scientific American's "Amateur Scientist" column.

"An Unusual kind of gas laser that puts out pulses in the ultraviolet" Scientific American, Amateur Scientist (June 1974)

This guy references it with regard to his TEA laser as well:

https://www.cornellcollege.edu/physics-and-engineering/pdfs/...

This seems like a fun project, but I don't really understand what's going on here.

I see a bright light, a lot of metal and electronics, and then what appears to be a laser point. Scientifically, what's going on here?

Long thins strip of air between aluminum electrodes is electrically excited to produce ultraviolet light, but because it's very long and thin, it starts lasing action (photons travelling along the length of the channel induce air to emit more photons in phase and travelling in the same direction) which produces laser beam. It's essentially ultraviolet laser from projector transparency sheets, some tinfoil and high voltage source.

From what I understand, there is a discharge along the length of the electrodes which would excite the medium (air) in the gap. Now photons are being emitted randomly in all directions. This means also in direction along the gap. This is important since these photons will interact with more of the excited medium and thereby stimulate emission of additional photons, leading to 'lasing'. As long as there are excited molecules (or atoms) left, this is a self-amplifying process. (Lasers are basically clever contraptions to keep these excited states populated)

Notice that there is no resonator with mirrors at each end as you would see in other lasers.

It is also a UV laser which means you can not see the beam without it interacting with a substance that can convert UV to visible light. That's dangerous because you could inadvertently look into the beam (via reflections from somewhere in the lab!) and take eye damage.

sign outside a physics lab:

"Don't look at laser through remaining good eye"

And there I was hoping this would be about using tea as a gain medium to make a laser. Green tea is slightly fluorescent, right?

Yeah, the title is "Simple Homemade T.E.A. Laser", not "Simple Homemade Tea Laser", and that seems like a weird change to make.

How I would go about this: if you are not interested in learning about dye lasers yourself, I would find a specialist working with dye lasers on Twitter and ask them to settle "an argument with a friend" that green tea does not work as gain medium. Then wait and hope that you have nerd-sniped them. With a bit of luck you can read a paper about the topic one day. ;)

Reply on news.ycombinator.com