Lightning in the lab: Femtosecond laser generating plasma in air

[FBElectronics]

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[dsheludko]

@DevilMaster I used Watts because it's the SI unit for power. As you state, a bit of 4th grade maths can easily convert between peak and average power, but in order to ionise air and create the plasma, it's the *peak* power that's important, not the average, which is why I stated it. Also, as stated in the first sentence of the description, the rep rate is 1kHz, so you can work out the average power from that.

[DevilMaster]

Why would a scientific video use watts when talking about a pulsed laser? That's what Information Unlimited and Future Horizons do to inflate the figures and impress the n00bs.

100 GW are 100000000000 W; 35 fs are 0.000000000000035 s. This means that a single pulse gives out 0.0035 J of energy. Now, to know how the laser *really* performs, all that's left to know is the quantity of pulses per second.

[nictheman144]

I believe plasma is what happens if God takes Acid. trippy.

[frankensteinmoneymac]

God...for a second I thought the laser pattern on the wall WAS the plasma!!!! LMAO!!! Damn...that woulda been incredible!!!!...just big ol' ball of orange plasma....Guess the plasma is just the tiny little dot though....still cool though.

[AtomchildMusic]

If we could find a way to place thousands of these focused plasma dots in a 3 dimensional array without interfering with eachother, we would be one step closer to holographic imagery.

[AnselmoFanZero]

Laser guided energy? Anybody?

[dreamyear]

that looks like portal to another world

[boxa888]

real artificial ball lightning! nice! u should try making it scan fast in the air and make a hologram, u would be the first to make a real hologram, probably really dangerous but it would amaze!!

[EinYamakasi]

1kHz buzz you can hear is the thunder, repeated 1000 times per second (the laser pulses at 1kHz). Is that so? I wonder if it's possible to modulate that to produce useful sound, like a modulated spark-gap (plasma speaker). Fun food for thought...

[Oatinator]

100GW????? I didn't know such a powerful laser existed.  Couldn't that like cut someone in half?

[ashish19]

@Oatinator This 100 GW is the peak pulse power. In the continuous mode, this will be of the order of a few Watt I guess !

[Oatinator]

@ashish19 oh, thanks lol

[aVoNgfx]

@Oatinator Even more powerfull PULSED lasers exist. The thing is, that it accumulates the energy in a short pulse which otherwise would be spread over a longer timespan with a constant-wave laser.

Let's say your pulse energy is 1J and pulse-length 1 ns, then you end up with 1 GW of power for every pulse. If you repetition-rate is 10 kHz, then the same laser in constant-wave mode would have an output of only 10 mW.

[Oatinator]

@aVoNgfx Thanks for explaining!

[RedRoost80]

100GW!?!?!?!?!?!?!?

[AnselmoFanZero]

35fs is not much. What pulseduration is needed for a pulsed UV laser to ionize air? Raw beam...unfocussed. RepRate maybe 20hz...beam diameter 1mm.

No idea how much caps I might use, because more caps mean more energy mean longer pulse.

Any idea?

[TrollSturm]

So...if I put my hand in the beam...would it just burn all the skin and flesh off, or explosively flash boil? :D

[laitela01]

yeah, I wanna see something throwed at it, nobody cares about this boring shit

[Anon701]

@laitela01 Well, someone has been spending too much time in the sewer of the internet. Why are you commenting if all you have to say is 'lol, sux'? Go back to /b.

[limeroundup]

I've seen this at the university of Groningen. The sound is really annoying :P

[iminyourbasement]

100 gigawatts lol thats remarkable

[SpecklePattern]

That will produce X-Rays. Don't stare the plasma very close :) We have also fs laser at our university.

[magx1]

What is the wavelength of this laser?

I can see red and green on the wall, but you mention that this is the result of a non-linear process. So is the wavelength invisible before it passes through the focal point where the plasma occurs?

[Analbeads369]

i went into this lab last year!

the guys there are pretty cool.

don't know if they can remember me/my group though.

we were the year 10's who came because of that ACORN program and there was like 6 or 7 of us. i was the short curly haired guy if you blokes can remember me haha.

pretty crazy though.

[martiallaw09]

Do you throw stuff into it for the lulz?

[whatthi]

i am also intrigued by how the negative ions in the air manage to electrify the lets say the acidity of the metal plates which is pretty much what Einsteins law would have predicted in conjunction to +10000 megahertz of waves

in other words i have no clue what the fuck i just said..but thats awesome!!!ill take 3

[niermem2]

ha we have exactly the same setup, Tsunami and spitfire, from newport spectra-physics. We are in Germany though and use this for 2 photon spectroscopy.

[Mangina9000]

There's a skull in the middle of the vortex! STEP AWAY FROM THE VORTEX.

[10mintwo]

at a diffraction limited spot of 100GW, aren't X-rays a concern?

[dsheludko]

Perhaps... Too late now, I guess :) Anyway, was only on for a couple of minutes, flux is probably pretty low. Input beam waist was ~5mm FWHM, lens was f=40mm singlet, \lambda = ~800nm, I *think*... If you bother doing the math, let me know the answer!

[dsheludko]

Yeah cost is of that order. This was taken the day of installation, when we were having a bit of fun... It's primary use now is writing structures into optical fibers and such (optical communications and data processing/switching research).

[yunawind]

How much does such an instrument setup cost, and what is its real purpose? I'm guessing half a million USD?

[radiation500]

I understand that natural maser production, such as is found in thunderstorms, might also produce a plasma ball in the atmosphere, similiar to this laser effect, causing what we call ball lightning. Has anyone pursued this theory?

[AnselmoFanZero]

Plasma ball....right...would be "stable" for a ns.

[AnselmoFanZero]

Cool....reall cool.

[malruck246]

Hello, I am a physics student and I am very interested in this phenomenon. I'm working right now in my degree thesis and this is my topic. It would be nice if we could get in contact in order we could talk about the experiment and exchange data.

[kantikphil]

I always wondered how non linear effect are caused. I believe it is somehow related to the change of refractive index in a anisotropic material. Am I correct? Please let me know. I am doing a B Sc. in Engineering physics so please dont spare any details.