Think about this...

[Javalin]

Facepalm. Diode was the wrong word there. But that would make sense, quartz has a fairly high melting point if I recall... Wiki agrees at 1670 °C / 3038 F Would you have issues with thermal shock with quartz?

Also how feasible is it to ionize a beam rather than just at the focal point?

 

[pschlosser]

I hope one day something like this could be made.

That day has come and passed.

Multimode Directed Energy Armament System

 

[Alec]

Multimode Directed Energy Armament System: Science Fiction in the News
Hehe, now we just need to get it down to the size of a cardboard tube... And I'll be happy! xD

 

[Leodahsan]

Facepalm. Diode was the wrong word there. But that would make sense, quartz has a fairly high melting point if I recall... Wiki agrees at 1670 °C / 3038 F Would you have issues with thermal shock with quartz?

Also how feasible is it to ionize a beam rather than just at the focal point?

I don't really know if quartz would effectively be transparent to wavelengths emitted by a chemical laser. Thermal shock would be the smallest of your problems while dealing with plasma forming lasers and thunderbolt generating machines.

To ionize air around a beam, you need so many power ^ cm² (IIRC). Using a higher frequency laser (lower wavelength) would be easier (IIRC, planck constant * frequency = energy per photon) to achieve such needed power (which is around 8 TW/m^2, according to post #2 here Ionization of air with a laser).

edit:
read here

 

[cheech226]

Plasma torches, on the other hand, completely ionize the gas passing through the system, and make what is known as hot (ass) plasma. If you’ve never used a plasma torch or seen one at work, you’ve really missed something remarkable. It cuts through metal like a hot knife cuts through butter. Working with one can make you feel like a deity.

Plasma torches form a tiny rocket engine at the tip. A gas is pumped through a small nozzle where an electrical charge is applied to the gas. The gas becomes ionized, expands rapidly and turns into plasma. Its temperature is like 30,000F and travels at 20,000 fps. The tip focuses the gas into a lovely little blue point about two inches long.

The gas used need not be anything special. Nitrogen, Oxygen and Argon are pretty common. I cannot say for sure, but I don’t think there isn’t any substance it can’t cut. These are not to be confused with Oxygen-Acetylene torches that burn the acetylene to reach temperatures of 6500F.

in my trade we use plasma torches usually to cut stainless pipe or plate. my understanding is it is much like an arc gouger. a high amp electrical arc is made to the metal to be cut, kind of like a welding arc. air is blown at high pressure through a special nozzle that blows away the molten metal thereby cutting it. in my experience only conductive metals can be cut using this method. a ground wire must be attatched to the metal being cut to allow the current to flow.
we always have used air to blow the metal away, it's much cheaper than O2 or argon.