And then there are spasers.
As I recall, Widom-Larsen Theory for LENR involves surface plasmons...
Phonon Laser
Re: Phonon Laser
Pew Pew! Scientists Build Lasers Out of Sound, Call Them Phasers
Don’t expect to set your phasers to stun just yet. Light has the advantage of being able to travel through a vacuum, so a laser beam can easily go from its origin point anywhere else, even through space. Phonons require a medium to travel through, which means the phaser waves are confined to their device for the time being.
“We would lose the lasing if we get it out,” said Mahboob. “So we will need to figure out how to build structures onto the resonator that would allow us to transmit the vibrations out as energy.” Currently, he doesn’t have a good idea of how to do that, though other researchers will likely expand on the work and offer suggestions.