Is there such a thing?

[linux kid]

I would like to purchase some kind of light beam emmiter that allows me to control length of the beam, unlike the triditional lasers that must hit a surface.

[Danger]

There is not such a thing, and no known way to make one. It might theoretically be possible, with enough power on hand, to create a magnetic containment field for a low-pressure/low-temperature plasma inside, like a neon tube without the glass. That wouldn't count as a 'beam', though, and I'm not sure if it would work properly.
The only other thing that even vaguely comes to mind would be a pair of converging 180-degrees-out-of-phase lasers that end in destructive wave overlap, but that wouldn't be visible unless you inject a dust stream or something into it. Again, I doubt that it would work anyway.

[GOD__AM]

I would like to purchase some kind of light beam emmiter that allows me to control length of the beam, unlike the triditional lasers that must hit a surface.


Star Wars fan?

[berkeman]

Star Wars fan?
I was thinking the exact same thing. Maybe a flashlight, a tube and a mirror?

[DaveC426913]

Just so we understand what you're asking for, you want something that will send light out in a beam, say about three feet, and then beyond three feet, no light. As that it? And you don't want any physical mechanism (such as an opaque plate) at the three foot mark.

[fargoth]

how about using lots of lasers with different freqs, which are all very close to each other (the laser beams, not the freqs), and create something that looks like a sine wave in the wanted wavelength which is containd inside a packet in the desired length?

mathematically it's easy... i think things like that are being done in labs, but making it affordable and small enough to hold, is a bit tricky.

[Mk]

Get some red laser sine wave thingy's like you describe around an invisble axis to make it look like and asterisk *. Even if you had a physical barrier at the end, that would still be so sweet.

[pallidin]

Linux kid, I AM YOUR FATHER.

[Rach3]

No! Nooo! THAT'S IMPOSSIBLE!!!

[Rach3]

(that was in response to the OP's idea, not the Darth Vader quote)

[GOD__AM]

I'm still not posative the OP wants a light saber, as he hasn't replied, but I had an idea for making something similar. Using a compressed gas cylinder to inflate a semi-ridgid clear balloon in the shape of a saber blade, and choosing a gas that has a high reflective index (not sure what that would be), You could hit a button and have the blade inflate, then illuminate the gas with a laser (or any colored light source) in the hilt. Then using the right type of valve I think you could deflate the balloon by firing the compressed gas cylinder again. Kind of a klunky design, but I bet the star wars geeks would love it.:!!)

[linux kid]

I'm not a [big] star wars geek but it would be cool to have one of those light sabres.