In a poular science Artible, you can find what can be the equivelent of a mini lightsaber, it is a knife with superheated plasma and it is made as a medical tool to perform cuts while cauterizing the wound. Google it. It's nothing like a real lightsaber of course but hey its soemthing.
If we were going for a lightsaber in the laser sense, the 'No More Heroes' version seems the most plausible with an infinite loop lasers. Now how do to this is the tricky part, first off it wouldn't need to be a continous stream if you made the laser loops truly infinite, you would need to fire it off once and there you go, you have the equivelet of one cut because it would interrupt the beam. Then flik the switch again and pop out another one. While a continous stream may sound better to that plan the problemw ith that comes with the fact that you would probably fry your power source.
Also, another trick is the fact that in this situation where you have a super condensed high heat laser being reflected infinitely you would NEED some kiind of high quality material for the mirror, If you want a laser that can more or less cut through anything you need a material that can withstand that kind of heat. Normally this wouldn't be a problem with everyday lasers today, they are nowhere near that powerful. But believe it or not even though the light is being reflected off the mirrored surface it is still HITTING it. and in the situation that it is in a continous loop, it would be hitting it CONSTANTLY.
also, your light sabers would phase through one another, no dueling. The only reason that works in star wars is ebcause it is the electromagnetic field holding the blade in that shape that is hitting it (HIGHLY IMPROBABLE Btw)