After a decade of enthusiasm for laser weapons, the U.S. Department of Defense is backing off. The main problem is getting the weapons to the point where they can actually be used under combat conditions. That calls for rugged, reliable and mobile weapons. Lasers have too often failed in all three categories.
One of the biggest, and most expensive, disappointments has been the YAL-1, a powerful laser mounted in a Boeing 747 transport, and capable of burning a hole in a ballistic missile, up to 130 kilometers distant, as it is taking off. This destroys the ballistic missile when it is most vulnerable. The YAL-1 project was eight years behind schedule and $4 billion over budget when it was canceled last year as unlikely to be ready for use anytime soon. Also noted was the likely paucity of situations where enemy ballistic missile launch sites would be within range. The YAL-1 worked in tests, but was nowhere near needed levels of reliability for regular use. It's been the same with less powerful lasers, designed to knock down rockets and shells.
A persistent problem with combat lasers is generating sufficient electrical power to drive them. But the U.S. Army and Air Force have discovered that low power lasers can be pretty lethal battlefield weapons. For decades, the conventional wisdom was that you needed a high powered laser (as in instantly burning through the metal skin of a missile). But over the last few years, it's become obvious that slow burn (lower powered) lasers will do useful stuff like cause the explosives in shells, missiles and roadside bombs to go off. That was thought to be potentially very useful, but the U.S. Department of Defense conducted lots of tests in the last five years, only to discover that these cheaper, easier to use (because of the lower power requirements) lasers were also not yet ready for prime time. A lot of work was also done on lasers that can blind enemy sensors. This sort of thing has been around for years, but new, cheaper and more sensitive sensors are also more vulnerable to lasers. This didn't work out either.
While scaling back most efforts to develop laser weapons into systems that can actually be used in combat, the military is continuing to do a lot of basic engineering work. Breakthroughs in battery power and laser design can eventually solve a lot of the existing problems. Meanwhile, lasers continue to proliferate as measuring tools (laser range finders) and sensors (ladar). The laser weapons, it's agreed, are going to arrive later, rather than sooner.