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best wavelenght to ionize air

Alaskan

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I have been wanting a Ti:Sapphire rod for a long time, but the prices are fricken high! I've seen glass sapphire rods on ebay too, but not sure their application, anyone?
 



Seoul_lasers

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I have been wanting a Ti:Sapphire rod for a long time, but the prices are fricken high! I've seen glass sapphire rods on ebay too, but not sure their application, anyone?
We have a local company that grows Ti:Sapphire rods and YAGs. I wonder what I can get from them if I ask nicely. :thinking:
 

Seoul_lasers

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hello everybody,I want to build laser,focus the beam and turn air into plasma.

My problem is,I dont know what is the best wavelenght to do it with.I want a wavelenght that is most efficiently absorbed by air molecules.Please dont show me that chart of atmosferic absorption,its useless becose its about the light from sun that have to travell through all the atmospheric layers,spectral absorption from heigh of 100km to ground is something completly different to laser being used at sea level at distance of 10 cm.

What I learned so far ( correct me if I am wrong )

1. every type of atom ( nitrogen,oxygen,ozone,... ) have its own unique spectral lines,if you hit the atom with laser that have wavelenght like one of its spectral lines,then its going to be absorbed more,the laser is going to travell less distance,it is going to turn into heat in shorter distance

2. pressure and humidity affect the absorption at given freqency,something something about spectral line broadening due to water vapour,I am not sure


I was thinking,since nitrogen makes up the biggest part of air,hitting one of its spectral lines would be the best? I tried to google Nitrogen infrared spectral lines but I didnt find anything
Nitrogen spectra (in excited states such as in a TEA Laser setup) is 337.1nm.
That's a UV-A line emission.
IR is generally emitted by CO2, Yag, Ti:Sapphire, Nd:Yag etc..
As stated earlier in your other Radioactive material assisted laser ionization thread, CO2 can be pulsed in a TEA setup with a pulse forming network.
20-40Kvdc usually does the trick.

This would cause the air to break down easily.

Below are real world examples of pulsed lasers of varying wavelengths
causing air breakdown to occur. (this goes back to what I said earlier in the other thread about air breakdown
occurring more to do with power density rather than wavelength)

TEA CO2


Nd:Yag


@ 532nm with KPT on Nd:Yag


@ 248nm and 193nm using Excimer laser technology

 
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lazeristasUVISIR

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About 20 years ago our lab worked on a ionized light channel. It looked bright and long ~10 m -15 m. A laser was 1054 with ps pulses.
I've read about similar experiments using fs Ti:sapphire lasers and dreams to create channels in atmosphere to discharge thunderstorms. Don't know the current status :whistle:

As to the main question: it boils down to what is available technically - need lots of intensity >> what generates it >> Ti:sapphire and Nd:glass >> not very hobbyist friendly systems. :thinking:

It reminded one funny experience - long time ago I was aligning 2.7 um laser resonator, when it would be well aligned, it was possible to hear laser pulses :)
 
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Fonograph

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I wonder,if you send laser beam through thin optic cable,will the beam exit the cable already highly focused due to the thinnes of the cable so it doesnt even need focus lense? I reed the individual strands can be super thin and also have very big power carrying capacity.So theoreticaly can you send the laser into the optical strand and achieve similiar focusing like with focus lense?
 

Rivem

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I wonder,if you send laser beam through thin optic cable,will the beam exit the cable already highly focused due to the thinnes of the cable so it doesnt even need focus lense? I reed the individual strands can be super thin and also have very big power carrying capacity.So theoreticaly can you send the laser into the optical strand and achieve similiar focusing like with focus lense?
No. The optical properties of those fibers prevent them from carrying a collimated beam. You'd need a collimation lens at the end to get a beam.

That said, if the thin fiber is in direct contact with a target, it can have decent power density right at the termination.
 
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diachi

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That said, if the thin fiber is in direct contact with a target, it can have decent power density right at the termination.
Which can also cause burns to the end of the fiber making it pretty much useless. :beer:
 
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Fonograph

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why are focal lenses so wide? if I need to focus laser from 1mm wide fibre,do I really need 30mm wide lense?
 

diachi

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why are focal lenses so wide? if I need to focus laser from 1mm wide fibre,do I really need 30mm wide lense?
Where are you looking? It's easy to find them down to even 5mm diameter...
 

Fonograph

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but purely theoreticaly,if I have 1mm fiber,all I really need is 1mm wide lense,is that correct? Or is there something going on that I dont understand that makes is that you need wider lense than the width of the beam you want to focus.
 

Seoul_lasers

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why are focal lenses so wide? if I need to focus laser from 1mm wide fibre,do I really need 30mm wide lense?
I guess I am lost as to what you are trying to accomplish here.




Purely for theoretical reasons of course.....
 
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Encap

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I wonder,if you send laser beam through thin optic cable,will the beam exit the cable already highly focused due to the thinnes of the cable so it doesnt even need focus lense? I reed the individual strands can be super thin and also have very big power carrying capacity.So theoreticaly can you send the laser into the optical strand and achieve similiar focusing like with focus lense?
why are focal lenses so wide? if I need to focus laser from 1mm wide fibre,do I really need 30mm wide lense?
but purely theoreticaly,if I have 1mm fiber,all I really need is 1mm wide lense,is that correct? Or is there something going on that I dont understand that makes is that you need wider lense than the width of the beam you want to focus.
For what purpose? To what end? Why? as cyparagon asked in post #8

All the above questions are not questions about anything real -- just vague generalization based questions about daydreams/imaginings about lasers, fiber optics, and lenses.
Nobody is going to spoon feed an entire education on several large and complicated subjects which is not possible on a forum even if someone wanted to.
Do yourself and everyone a favor--take the time to learn enough to be able to attempt asking an informed and intelligent question about something more specific and real.
 
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LSRFAQ

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9g50-100 mJ of 3 to 7 nanosecond pulsed Yag will do it all day. If there is dust in the air for the plasma to form on. Far less power is needed if it's hitting my fingernail or business card.



For this you need a EO q-switch, an Ao style usually is too slow.

Used to be a real problem on some flash lamp pumped systems I worked on, @ 10 Hz rep rates.

Makes a tiny snapping sound, and a faint flash of cold white plasma. It is not an earth shattering nuclear reaction hanging in space.

Mind you these systems have a bullseye gradient oc coating on the master oscillator, making a very high quality beam.



S.
 
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