Only doing part of the filament was also most likely for comparison purposes; the untreated part of the filament was the "control".
If all the laser did was to make the filament a little thinner at that spot, it will get hotter at that spot (as the same current is going thru the entire filament). As the spot is a patch of higher resistance per unit length than the rest of the filament, and it may burn out at the bright spot. But doing the entire filament would just give you a lower wattage bulb, if the entire filament has the higher resistance per unit length.
So be careful before you run out and invest in this new technology...
