A key paper for those who subscribe to the SPP modality in LENR - which is operational in at least one form (the Holmlid effect) is: "Plasmonics with a Twist: Taming Optical Tornadoes on the Nanoscale" by Svetlana V. Boriskina (MIT). http://arxiv.org/abs/1405.1657
Boriskina provides insight into the plasmonic focusing mechanism - which is necessary to focus wavelengths of visible coherent light (in the range of green to yellow, or 535 nm to 580 nm) down to approximately 1 nm and below. She explains this by invoking an analogy of the 'photon fluid' (and magneto hydrodynamics) where light waves will be locally amplified and upshifted via convective vortex acceleration. The result is like an eddy current of photons up to a million time more powerful than before. Thus, the Holmlid effect is explained by trapped light which is swirled into optical vortices by EM fields. These are transitory tornado-like areas of circular/helical motion of flux. The result is magnetic fields of extreme local intensity (kilo-Tesla to mega-T.) which effectively compress and densify hydrogen into a new phase which can be well beyond metallic. Metallic hydrogen required compressive forces in the range of 500 GPa, but dense hydrogen requires at least an order of magnitude more force, which is well beyond the mechanical strength of a diamond anvil, for instance. The payoff is Holmlid's new phase of dense hydrogen which becomes stable, once formed, without added pressure. Metallic hydrogen is not stable in an unpressurized condition and immediately reverts to the gas. The specific resonance values for the vortex formation depend on the matrix metal. With Holmlid's experiments using iron-oxide matrix, the resonance value for photons is 535 nm which is green light. For palladium, using PdCl and LiCl electrolyte the strongest emission line is 542 nm which is yellow green. Electrolysis creates its own internal photons at the emission lines of the electrolyte. BTW - Boriskina apparently has no present connection to LENR per se, but as a theorist, she could become more important to the field than almost any other theorist (including Hagelstein) - to the extent that the SPP modality is shown to be correct. She appears to be relatively young which is bonus, should her insight prevail - since LERN field is aging rapidly. http://www.bio-page.org/boriskina/