[Ultra-Tech] Multi-Mode Laser

[vierasmarius]

Originally Posted by lwcamp

Modern lasers often make use of frequency doubling or tripling to change the beam color.

I was hoping you'd drop by to share your Death Ray wisdom. So, it sounds like it would be reasonable to allow a laser to switch between two frequencies without any additional bulk. How broad a range would this cover? Can such a laser be dialed for anything from IR to UV?

[Agemegos]

Originally Posted by vierasmarius

I was hoping you'd drop by to share your Death Ray wisdom. So, it sounds like it would be reasonable to allow a laser to switch between two frequencies without any additional bulk. How broad a range would this cover? Can such a laser be dialed for anything from IR to UV?

I suppose that if you had a laser operating at a wavelength about 1000 nm (in the near IR), frequency-doubling would get it to about 500 nm (blue-green), and frequency-tripling to about 330 nm (UV-A).

[MatthewVilter]

Originally Posted by Fred Brackin

In 4e the same name was given to a polychromatic visible spectrum laser that uses femtosecond pulses at a ultra-high cyclic rate to self-focus in normal atmosphere,

Are 4e Rainbow Lasers not hyperspectral?

*goes and looks* *looks up "polychromatic"*

Hard to say... I guess the fact that they only go 2 yards into water means...well it is normally blue-green that does and they do include enough of that to be "blue-white" so... I guess the other parts of the beam are needed to keep it focused or maybe the self focusing trick just doesn't work under water?

And I still don't know if they are hyperspectral...

Originally Posted by lwcamp

Modern lasers often make use of frequency doubling or tripling to change the beam color.
http://en.wikipedia.org/wiki/Second_harmonic_generation
http://en.wikipedia.org/wiki/Third_harmonic_generation
The most common use of this is probably with Nd:YAG lasers, which put out near infrared light at 1.064 micron wavelength. This is often frequency doubled to a green beam at 0.532 microns by shining the beam through a non-linear material. This can be surprisingly efficient - as of around a decade ago, industrial machining lasers would go from 30% wall-plug efficiency in the near infrared to about 20% wall-plug efficiency when emitting green light.

Luke

Originally Posted by Agemegos

I suppose that if you had a laser operating at a wavelength about 1000 nm (in the near IR), frequency-doubling would get it to about 500 nm (blue-green), and frequency-tripling to about 330 nm (UV-A).

Man...sometimes I start clicking explanatory links on a wikipedia page and quickly hit on something I know well and can work back to the page I started on feeling like I know what it is saying...this is not one of those times...

Still I take it that the introduction of a nonlinear medium and optics to deal with the resulting light would add some bulk to a design. I think that puts me on track for a 50% cost and mass add on.

Sound right?

[Fred Brackin]

Originally Posted by MatthewVilter

Are 4e Rainbow Lasers not hyperspectral?

If I weren't busy I'd go look up hyperspectral as I d0on't know what you mean by that. :)

"Polychromatic" was definitely the description I got and it meant a basically "white" light stretching over a continuous range of wavelengths going from perhaps somewhere in the near IR well into the visual..

These lasers (usually called femtosecond or Ultra-short pulse/USP in the real world). need to interact with air to self-focus. I don't believe water will produce the same effects at all.

[lwcamp]

Originally Posted by vierasmarius

I was hoping you'd drop by to share your Death Ray wisdom. So, it sounds like it would be reasonable to allow a laser to switch between two frequencies without any additional bulk. How broad a range would this cover? Can such a laser be dialed for anything from IR to UV?

Originally Posted by Agemegos

I suppose that if you had a laser operating at a wavelength about 1000 nm (in the near IR), frequency-doubling would get it to about 500 nm (blue-green), and frequency-tripling to about 330 nm (UV-A).

That's pretty much what I has in mind. There are also some lasers (such as Ti:sapphire) that lase well across a fairly wide frequency range. Free electron lasers can be tuned across a quite broad frequency range - if you could miniaturize one of these from something that fits in a warehouse to a hand-held weapon, you could easily span infrared to ultraviolet.

In real-life, using ultraviolet beams in air will be problematic because at the high intensities needed for burning through people, you get significant two-photon absorption which saps a lot of energy from your beam.

I did write up some realistic beam weapons for GURPS, under the assumption that beams propagated using known physics but that you could super-science up powerful emitters and batteries and focusing arrays
http://panoptesv.com/RPGs/Equipment/...eamWeapons.php
You might find some inspiration there. Definitely not RAW, though.

Luke

[Agemegos]

Originally Posted by lwcamp

That's pretty much what I has in mind. There are also some lasers (such as Ti:sapphire) that lase well across a fairly wide frequency range. Free electron lasers can be tuned across a quite broad frequency range - if you could miniaturize one of these from something that fits in a warehouse to a hand-held weapon, you could easily span infrared to ultraviolet.

A couple of years ago I was talking with a bloke from the University of York who told me that he had in his lab in some sense the shortest-wavelength laser in the world*†‡. He was full of admiration for FELs, and told me that they would be wonderful things when someone got them working properly.

* It only existed for a picosecond at a time — while something was explosively evaporating in the beam of his pumping laser — but put out about a terawatt of beam power while it did, at vacuum-UV wavelengths getting on for soft x-rays.

† One of his grad students had been in touch with the Guinness Book of Records. They had come across with a certificate, but weren't going to put the team and their laser into the book. :(

‡ He didn't seem to expect to hold the record for long.

[lwcamp]

Originally Posted by Agemegos

He was full of admiration for FELs, and told me that they would be wonderful things when someone got them working properly.

I have a proposal in to see if I can get something similar to a free electron laser to work, and if it does work it would be very compact. Early versions would only be millimeter wave, terahertz, and long wave IR, though, and it probably wouldn't be intrinsically tunable over a wide range like a real free electron laser. We'll see if this gets funded or not.

Luke

[Verjigorm]

Originally Posted by lwcamp

I have a proposal in to see if I can get something similar to a free electron laser to work, and if it does work it would be very compact. Early versions would only be millimeter wave, terahertz, and long wave IR, though, and it probably wouldn't be intrinsically tunable over a wide range like a real free electron laser. We'll see if this gets funded or not.

Luke

And then we mount it on the lizards?

[The_Ryujin]

Originally Posted by Verjigorm

And then we mount it on the lizards?

And I, for one, welcome our new lizard overlords.

[Anthony]

Originally Posted by lwcamp

I have a proposal in to see if I can get something similar to a free electron laser to work

What definition of 'work' are we using here? It's not like free electron lasers don't already work. Work as weapons?