"The ultra-violet laser, or the 'Xaser' can be more effective in some situations. However, due to the problems of creating lenses that can reflect X-ray waves, the Xaser has to get all it's grunt-force in one pass of the gain medium. While this might be a helpful thing for ground level simple rifles, mutli-lensed sniper rifles and tank weaponry benefit from the increased focus and precision that comes from having several lenses. Additionally, if you want your Xaser to be more powerful, you need a more powerful energy pack, which has its own size or technological drawbacks. Carting around a small nuclear reactor sucks on multiple fronts.
While the universe is broad and technological capabilities between people are radically different, there might be a power pack of sufficent power to allow an Xaser to pull all the requisite energy in one pass, but that is something you'll be finding in the most advanced nations in the universe. On ground level, for you and me, it's not something you should hold your breath for"
She'd scrawl more equations on the board and then point to them with her laser pointer. It was a handy thing, lasers.
"As for effectiveness and efficiency, it is, like everything, dependant on the situation. A solar-charged or fusion breeder pack for a standard assault rifle sized laser gun can store up to two hundred shots in a single thirty bullet mag size, recharges over time, weighs significantly less and requires less skill to be accurate with, has less moving parts and thus greater reliability on the ground, blows people up with flash-boiling, and can be modified to different power settings at the flick of a switch. While anti-infantry weaponry against heavy armour is a dumb decision for anyone to make regardless of what weapon you are using, there is some benefit to volleyed laser fire against tanks and power armour. The compounding electromagnetic photons hitting the side can interfere with the internal electronics. You'll still want to use proper anti-armour weaponry like a Guass Bazooka or a heavy plasma cartridge if you can, but you are not completely helpless if you are deprived of these weapons, so long as you have the rest of your platoon with you. Additionally they are decent budget anti-aircraft weaponry, as beam cohesion is rarely an issue in the modern world unless it's made in a cave with a box of scraps. You probably won't do much damage, but the same electromagnetic photons can cause a stall, which is infinitely more deadly for a guy in the sky than a guy on the ground/
So, for people that need to travel light and fast like my flight suit or are situated away from a supply zone for extended periods of time, a laser rifle is a blessing. It does not cover every requisite situation you might run into, but for a standard infantryman on the ground, it is a good gun to be using against other standard infantrymen on the ground"