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Solid-state lasers

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Solid-state lasers

Unread postAuthor: saefroch » Mon Apr 04, 2011 2:17 pm

Laser technology was mentioned previously here, and I thought I'd try to expand on it. This is really NSGR, but I figure this forum is one of the few places there could be a really intelligent discussion of them. I've got a few questions to possibly start a discussion...

1) Has anyone done work with building solid-state lasers before?

2)
Wikipedia wrote:Many of the common dopants are rare earth elements, because the excited states of such ions are not strongly coupled with thermal vibrations of the crystalline lattice (phonons), and the lasing threshold can be reached at relatively low brightness of pump.
I understand that lasing is based on bumping electrons up to a higher energy state, then using the emission spectrum. What I'm curious to know is why seemingly all solid-state gain media are highly crystalline or glassy solids doped with rare-earth metals?

3)Has there ever been any investigation into using a chemical reaction to optically pump a laser?
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Unread postAuthor: ramses » Mon Apr 04, 2011 4:32 pm

There are chemically pumped lasers, but I don't know of any that use light produced by chemicals to pump a laser. Typically, the time of the burst of light that energies the laser is extremely short. I remember discussion about too long of a pulse being ineffective; the extra energy does not actually contribute to the laser light.
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Unread postAuthor: saefroch » Mon Apr 04, 2011 6:56 pm

Do you happen to recall why the long burst does not contribute to light/energy output? I know that some YAG and gas lasers are run for long periods of time, and are presumably pumped during usage...
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Unread postAuthor: ramses » Tue Apr 05, 2011 8:12 pm

I was thinking of dye lasers.here's a link I'm not completely sure if this also applies to YAG or gas lasers. I know gas lasers can be ran (run?) CW, at least if electrically stimulated.

Actually, the same site' YAG page uses a conventional flashlamp that probably discharges in about 1 millisecond, (as reported on the dye page, and my own experience). As seen here, ~50mg of magic dust can combust pretty much completely within 1/1200 of a second. I'm not sure I'd be inclined to expend magic dust within an inch of a YAG rod, however. :roll:
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Unread postAuthor: mobile chernobyl » Tue Apr 05, 2011 9:23 pm

Interesting - I had pondered utilizing the effect you get when you rapidly compress a noble gas utilizing a majik dust to pump a laser rod.

EDIT - Interesting little wiki about this effect: "The photography of explosions and shock waves is made easy by the fact that the detonation of the argon flash lamp charge can be accurately timed relative to the test specimen explosion and the light intensity can overpower the light generated by the explosion itself"


You'd need to focus the light onto the rod however and containing the pressure/focusing the light may be a challenge and most certainly sacrificial so It's not something I'd be able to pursue anytime soon.

Nice to see someone else is thinking about it lol
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Unread postAuthor: saefroch » Tue Apr 05, 2011 10:41 pm

I wasn't really thinking of majik dust here, but just that almost any sort of metal with a capacitor dumped onto it will generate more total electromagnetic energy that just dumping it onto even a noble gas in an attempt to generate a specific spectrum.

In any case, I'm sure you could dump more than 100J into a solid state laser using some sort of chemical interaction, and much less capacitance. Actually, the head of the physics department where I'm going built a large fernell mirror and managed to convert 89% of incoming sunlight into heat energy on water. I suppose it may be possible to build a similar fernell mirror with much smaller panes to direct the light emitted from a chemical reaction, and if it is not producing any gaseous product, I don't see why the mirror wouldn't survive.

(bit iffy on the below, mods feel free to delete)
My original idea was to just pump a vast amount of energy though a solid magnesium turning by shorting a capacitor, which might be workable because Mg seems to have one clearly defined major emission band at about 520nm. Then the idea occurred to me to add an oxidizer or something to make the reaction go faster or be more energetic, but that may be destructive to the device, but it may be possible to pump some extra oxygen into the local atmosphere, no?
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Unread postAuthor: ramses » Wed Apr 06, 2011 3:47 pm

The mirror might be doable. doesn't sound like much fun to construct, though.

With regard to photographing explosions, it has been done with about 10 joules discharged into normal air at atmospheric pressure
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Unread postAuthor: saefroch » Wed Apr 06, 2011 5:37 pm

So far, I think I can handle building a capacitor bank and probably a mirror device of some sort, and maybe even the laser tube itself, but I'm a bit lost on how (if at all) I could construct a gain medium. Probably the most logical option would be to just try to pump an old Nd:YAG, but if the Mg idea is to work, ideally the gain medium would have an absorption band around 585nm, and nothing I can find has such.

Is it possible at all to have a gain medium doped with Mg to absorb the emission of an Mg reaction? If that's even possible, is there any way for an amateur without advanced facilities to make a gain medium? The doping shouldn't be too much of an issue, but the glass/crystal....
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Unread postAuthor: ramses » Thu Apr 07, 2011 8:52 pm

Dye cells can be made. Basically, it's a solution of some organic dye. The issue becomes, then, flash duration. As that link said, dye lasers like a quick burst, which is not possible with reasonable combustion. (Without magic dust). I'm not sure about Mg doping for MG spectrum. If anything, you'd want to dope with MgO, since that would be most likely be a big part of your emission spectrum.

Most of what I have is theoretical knowledge, which I acquired before scrapping the idea of making a laser.
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