There are two ways off the top of my head (assuredly there are more): (1) use two lasers; or, (2) the geometry of a laser is hour-glassed shaped, so only the “n

There are two ways off the top of my head (assuredly there are more): (1) use two lasers; or, (2) the geometry of a laser is hour-glassed shaped, so only the “neck” may have sufficient energy density.