  Recent theoretical and experimental studies highlight the possibility of new
fundamental particle physics beyond the Standard Model that can be probed by
sub-eV energy experiments. The OSQAR photon regeneration experiment looks for
"Light Shining through a Wall" (LSW) from the quantum oscillation of optical
photons into "Weakly Interacting Sub-eV Particles" (WISPs), like axion or
axion-like particles (ALPs), in a 9 T transverse magnetic field over the
unprecedented length of $2 \times 14.3$ m. No excess of events has been
detected over the background. The di-photon couplings of possible new light
scalar and pseudo-scalar particles can be constrained in the massless limit to
be less than $8.0\times10^{-8}$ GeV$^{-1}$. These results are very close to the
most stringent laboratory constraints obtained for the coupling of ALPs to two
photons. Plans for further improving the sensitivity of the OSQAR experiment
are presented.
