Earlier this month, reports from the South China Morning Post unveiled China's purported new laser weapon, a "laser AK-47" that sounds almost impossibly portable and powerful.
Laser (and laser gun) expert Styropyro has taken his knowledge on the subject to form a strong technical critique. In short, it's nearly impossible to create a laser with the characteristics the report describes. What's more, making such a laser portable is much harder—even impossible—considering the limits of modern battery tech and the size of the weapon according to the report.
For starters, it's hard to find a theoretical wavelength of laser that fits the report's laundry list of claims: that the beam is invisible, can pass through glass, can light clothes on fire, and can burn skin. Infrared lasers can light matches, for instance, but are simultaneously harmless to human skin. A laser that lives up to the hype would have to hit a tiny frequency sweet spot, one that's made even smaller by the Geneva Convention's prohibition of laser weapons that blind. Though that apparently hasn't hampered China's laser research in the past.
Even with those issues set aside, the laser is also suspect for its impossibly light and compact design. Assuming no sci-fi power source is involved, the batteries to power such a weapon would need to weight four or five times more than the entire gun's reported three kilogram weight. And as a cherry on top, the claims the gun could light gasoline on fire from a distance are suspect too. Lasers are notably awful at lighting fuel on fire, :
For now it's impossible to know how much truth there is to China's claims. Laser weaponry does in fact exist, but the blasters we know of are generally designed as defensive, vehicle-mounted weapons. But whatever it is that Chinese engineers may have cooked up, the physics suggest there are quite a few caveats.