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Excimer laser design

by rppearso
Tags: design, excimer, laser
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rppearso
#1
Dec20-11, 11:21 PM
P: 105
Does anyone know if it is possible to design an excimer laser that produces a continuous beam well into the UV frequency range (enough to througly ionize the air in the path of the beam). I have been reading up on excimer lasers and it sound like they operate in pulses, which may be ok for the experement I am trying to set up but would prefer continuous.

Does anyone know of any texts that have detailed designs of excimer lasers. I have heard that the flash tube has to be capable of handling up to 5 bars of pressure and high temperatures due to the nessicary frequencies of the elecrical pulses that are fed to the gas. I could design (hopefully) an oscelator to get the high frequency electrical signal but I was reading that the electrical contacts run the lenght of the flash tube in order to ionize the gas so this would be something that would need to be in the design spec of the glass tube.

Also can you buy XeF or the other nessicary gases, are they outragiously expensive? I am guessing that you can mix Xe and F in the flash tube and after the first use they will bond from the elecrical excitation since thats the only way to bond a noble gas as they are chemically inert. I am worried that you either cant buy these gases or they are cost prohibitivly expensive also are they toxic enough to kill you if the gas is released of if you screw up some how?

I was looking into just buying a UV laser but what I found was cost prohibitivly expensive (~30 grand). I was going to contact a glass company to see what it would cost to have the flash tube made but want to have specific design specs to make sure I get what I need before I spend any money.
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RocketSci5KN
#2
Dec21-11, 02:03 PM
P: 163
I don't think there is any chance for you to make an excimer laser... When I was in high school, I tried to make various lasers from the Amateur Scientist articles in Scientific American periodicals. Check all old issues for a N2 laser pre 1980 - this was a pulsed UV laser that you could make, but it does involve high voltages, so be very careful. The gain was high enough IIRC, that mirrors were not needed.
rppearso
#3
Dec21-11, 05:50 PM
P: 105
Quote Quote by RocketSci5KN View Post
I don't think there is any chance for you to make an excimer laser... When I was in high school, I tried to make various lasers from the Amateur Scientist articles in Scientific American periodicals. Check all old issues for a N2 laser pre 1980 - this was a pulsed UV laser that you could make, but it does involve high voltages, so be very careful. The gain was high enough IIRC, that mirrors were not needed.
I dont think anything is impossible, its just a matter of finding suppliers to make the glass quartz flash tube and reflection of UV is not impossible. I need to push through with a design because my over all experiment/invention is dependant upon having a UV laser that operates well within the UV range. I read up on the N2 lasers which operate right on the edge of the UV range and im not certian if that is adaqute to create a beam that highly ionizes air.

Gordianus
#4
Dec22-11, 08:49 AM
P: 217
Excimer laser design

Excimer lasers rank among the most complex ones. Several companies manufactured them but very few succeeded. As far as I know population inversion has only be obtained in a pulsed discharge because the input power density is very large.
Of course, nothing forbids you to spend time and money in such a development. I'd suggest reading:Excimer Laser Technology
sophiecentaur
#5
Dec22-11, 08:58 AM
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I feel I should point out the health and safety issues with lasers. I have heard that the UV from N2 lasers is particularly nasty. At one time, people used to take the dangers more seriously. Now, with the easy availability of very low powered laser pointers, people have forgotten just what they can do to you.
It's one of those activities that need a lot of expertise to undertake safely, I think.
rppearso
#6
Dec23-11, 03:29 PM
P: 105
Quote Quote by sophiecentaur View Post
I feel I should point out the health and safety issues with lasers. I have heard that the UV from N2 lasers is particularly nasty. At one time, people used to take the dangers more seriously. Now, with the easy availability of very low powered laser pointers, people have forgotten just what they can do to you.
It's one of those activities that need a lot of expertise to undertake safely, I think.
The safety issues do concern me, the flash tube would have to be shielded and the shielding should have an internal aluminum coating to reflect the radiation back into the tube. I have found a place that sells high pressure glass tube I just have to figure out how to "weld" an end cap on and place the electrodes. Also it is key to get the dimer or excimer at modest pressurs of around 50 psig to get higher gas density which means I have to install a valve on the tube and find a way to get a hand pluger pump with a small pressure gauge where I can close the valve as soon as the tube reaches pressure and disconnect the pump. I have read that getting the population inversion to pump fast and drop energy states slowly is a function of the combinations of gas that you use, I have read that Ar2 have got wave lengths as small as 125 nm. The power supply would have to be GREAT in order to keep the excited states populated as stimulated emission is causing them to drop down.

I will definitly check that text refernece out. Another challenge is the electrodes inside the laser, I am guessing they would have to be made out of pure platnum or irridium to prevent deradation at high current and temperatures, maybe tunsten/titanium?

I am a chemical engineer with a PE and simultaniously working on a masters in EE while researching lasers. So im not a yokle in a garage lol.

Also how do you measure the wave length of a laser once you have built it?
sophiecentaur
#7
Dec23-11, 05:28 PM
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Quote Quote by rppearso View Post
The safety issues do concern me,
Well, I think they should concern you. It would be better, rather, if you had replied that you would take them into account - which is what happens in properly run laboratories. There may be other people than yourself involved and it would hardly be fair not to consider them. They may not be aware of the situation.
In fact, if you are planning to operate in a ligit lab then there are legal issues if you don't take the right precautions. It's not smart to act like a cowboy - 'qualifications' or not.

A non-yokel would probably have heard of a spectrometer.
Dmytry
#8
Dec24-11, 09:19 AM
P: 505
Fluorine is very nasty and reacts with all kinds of stuff including the electrodes, pumps, tubes, et cetera. Also, the population inversion requires very high power, which may be unsustainable for continuous operation due to things melting. I don't think anyone makes continuous excimer lasers.

Are you by chance building a zap ray? ;) The kind that ionizes path through air with the laser then puts high voltage through it.

With regards to eye safety of very short pulse lasers (like nitrogen), there's secondary effects such as hydrodynamic shock inside eyeball, which greatly increase damage over what would be expected for given energy.
rppearso
#9
Jan27-12, 12:54 AM
P: 105
Quote Quote by Dmytry View Post
Fluorine is very nasty and reacts with all kinds of stuff including the electrodes, pumps, tubes, et cetera. Also, the population inversion requires very high power, which may be unsustainable for continuous operation due to things melting. I don't think anyone makes continuous excimer lasers.

Are you by chance building a zap ray? ;) The kind that ionizes path through air with the laser then puts high voltage through it.

With regards to eye safety of very short pulse lasers (like nitrogen), there's secondary effects such as hydrodynamic shock inside eyeball, which greatly increase damage over what would be expected for given energy.
That is what I would hope to build, I have worried about things melting. Would the glass litterally melt? Will Fluorine react with irriduim, it is a metal know for its non corrosivity and non reactivity. For power if I cant do it with a dedicated generator then I was thinking of a 6 cylinder run out air craft engine attached to a generator.

Maybe the laser would need to be cooled.

Also I have concerns with the resistance of ionized air and how much damage would actually be incured at say 10-20 miles away, would suck to invest a bunch of time and money to have the experement be an epic fail.

It is unlikely this will be done in a "lagit" lab but rather in my garage, dealing with fluorine and clorine I may have to put in a fume hood.

high velocity weapons have been around so long that its like fighting with swords.
RocketSci5KN
#10
Jan27-12, 05:18 PM
P: 163
Sorry, but the fact that you are unable to correctly spell Iridium and Chlorine prove that you don't have the educational background to even attempt a project such as this. Besides, no one AFAIK has built a high power CW Excimer laser. If the high voltages don't kill you, the extremely toxic gases might. Go take some college level classes in Laser theory, chemistry and high voltage electronics - they will save your life.
rppearso
#11
Jan28-12, 06:31 PM
P: 105
Quote Quote by RocketSci5KN View Post
Sorry, but the fact that you are unable to correctly spell Iridium and Chlorine prove that you don't have the educational background to even attempt a project such as this. Besides, no one AFAIK has built a high power CW Excimer laser. If the high voltages don't kill you, the extremely toxic gases might. Go take some college level classes in Laser theory, chemistry and high voltage electronics - they will save your life.
I am not planning on doing this for a few years and I am taking the requisite EE classes and plan to get a masters in EE eventually (with an area of special interest in devices and lasers and a class or 2 in advanced electromagnetics with the requisite math), I checked out excimer laser technology on interlibrary loan so will go through that as well. I am a chemical engineer but that does not mean I know every interaction between every single element, I will eventually google it and read up on it but I was hoping to get more academic info from this forum than boarder line flames. Spelling aside I am well on my way to doing this one way or another. We need a game changer in modern warfare, not a bunch of debbie downers saying we cant.

My BIG question is, lets assume that a continuous UV beam could be produced (or at least pulses long enough to send electricitiy through) would the resistance through the air be too great for there to be enough current say 10-20 miles out to knock down a plane in one shot, just turn it into a fire ball, can capacitors get that great of a voltage to create such currents? If not then its not really relavent even if you could produce a continuous UV beam.

Hopefully the boarder line flames will get dialed back a bit in order to have a lagit academic discussion. I understand there are safety issues but thoes can be delt with so long as the project and the end results are feasable.
sophiecentaur
#12
Jan29-12, 06:00 AM
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One of these days, when I have become a competent artist, I may paint the Sistine Chapel. Meanwhile I'll accept what the experts have to tell me about Art.
I suggest you get the appropriate education before you launch out on too many SciFi ideas - or before you can show that they are not just fiction.

If you think that a Laser is a good potential 'Ray-Gun' weapon, perhaps you could reflect on the actual (incredibly low) Efficiency of the Laser process. A laser that uses an electrical power supply is pretty much out of the question for this reason. Otoh, a chemical laser can be and has been shown to produce a vaguely useful portable source of laser radiation. The 'inefficient' bit of the process is carried out 'back at the ranch' and the energy is stored in chemical form and much more highly concentrated.
berkeman
#13
Jan29-12, 06:15 PM
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Quote Quote by rppearso View Post
I am not planning on doing this for a few years and I am taking the requisite EE classes and plan to get a masters in EE eventually (with an area of special interest in devices and lasers and a class or 2 in advanced electromagnetics with the requisite math), I checked out excimer laser technology on interlibrary loan so will go through that as well. I am a chemical engineer but that does not mean I know every interaction between every single element, I will eventually google it and read up on it but I was hoping to get more academic info from this forum than boarder line flames. Spelling aside I am well on my way to doing this one way or another. We need a game changer in modern warfare, not a bunch of debbie downers saying we cant.

My BIG question is, lets assume that a continuous UV beam could be produced (or at least pulses long enough to send electricitiy through) would the resistance through the air be too great for there to be enough current say 10-20 miles out to knock down a plane in one shot, just turn it into a fire ball, can capacitors get that great of a voltage to create such currents? If not then its not really relavent even if you could produce a continuous UV beam.

Hopefully the boarder line flames will get dialed back a bit in order to have a lagit academic discussion. I understand there are safety issues but thoes can be delt with so long as the project and the end results are feasable.
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