DEW available to the US military for 20 years?

When I was reading the short snippet of an article here.

Much work has to be done on understanding the effects of these types of weapons, army officials said. The US has had a classified directed-energy weapon for 20 years but it has never been used because commanders have been unsure what the effect on people would be, said Brigadier General Philip Coker, director of capabilities developments at the Futures Center, Training and Doctrine Command.

What is it? I've worked on DEW (directed energy weapon) before at HELSTF: big mucking chemical lasers. The Solid State Lasers from Livermore were just coming in a month or two after I left. I ahve to wonder though what has been around for 20 years for the US military to use?

Talk about piqued interest!