The most promising approach for detecting WISPs (Weakly Interacting Slim Particles) is to use their small coupling to photons, which detection is easy, even at the single particle level. This is what is done in “light shining through the wall” experiments, which are based on the probability that a photon may be converted into a WISP, which would traverse a light-tight wall without interacting, then have a chance of being converted back into a photon with the same frequency and direction as the original one1. Because of the smallness of the WISPs-photon couplings, it is valuable to use the highest photon fluxes available together with a high magnetic field. In the near future, another interesting hidden-sector particle can be searched for on laser facilities, namely a hidden-sector photon (HP), also called paraphoton or dark photon. Indeed, the recent WMAP-7 observations and interpretations2 hint for an extra neutrino-like particle (the total number of neutrino species is found to be 4.34 ± 0.87 with 68% Confidence Level), which could be accounted for by a hidden photon with a mass μ and a HP-photon coupling χ in the parameters range accessible with laser shots. At ELIBeamlines, there will be a 1.5-kJ laser (L4) running at 1 shot per mn; it is therefore possible to have a dedicated LSW experiment inside one of the facility rooms that would take advantage both of the large number of photons delivered and of the “high repetition rate” of this laser.