Laser fields were shown to enhance the fusion yields, and the mechanism of this enhancement was explained. Low-frequency lasers are more efficient in enhancing fusion than high-frequency lasers.
I have not read the paper, but I will throw caution to the winds and speculate...
When two identical, coherent light beams travel in opposite directions (counter-propagating), they interfere to create a standing wave pattern. There will be nodes at helf-wavelength intervals, If the beams are vertical, the nodes will be in horizontal planes. Between the nodes the electric field oscillates. If this is within a plasma, the electric field will cause the ions to oscillate horizontally. Between a given pair of nodes, all the ions will be accelerated in the same direction. However, just half a wavelength higher or lower, the ions will be accelerated in the opposite direction. If a given ion has some vertical velocity and crosses a node at the right time, it could collide with an ion that has been accelerated in the opposite direction. This will be happening at every node. The lower the laser frequency, the longer the ions will accelerate and (for a given electric field strength), the higher velocity they will reach. The best laser frequency would also depend on the plasma temperature, such that a typical vertical ion velocity would carry it from one node to the next in a time similar to the oscillation interval.
I have not worked out any numbers, much less convinced myself of an improvement by several orders of magnitude.