Vacuum is an active medium whose reaction to an electromagnetic field can reveal a major physics. It is the siege of field fluctuations and virtual processes. It may lead to non-vanishing expectation values for field operators, signaling condensates. It may be populated by particles, that are predicted in many extensions of the Standard Model of particle physics but that have escaped detection, among which the axion (that would explain why the neutron does not show a measurable electric dipole moment), a plethora of axion-like particles (alps), scalar as well as pseudoscalar, predicted in supersymmetric or string theories, and more exotic fields quanta such as the chameleon.
A number of phenomena associated with the quantum fluctuations of the electromagnetic field and virtual electron-positron processes have been found out, such as Casimir effect, Lamb shifts and anomalous electronic magnetic moment. A vacuum magnetic birefringence has also been predicted and awaits experimental confirmation. Its measurement is a technical challenge, but will allow confirming quantum electrodynamics to an unprecedented precision and will reveal possible contributions from virtual axions or alps. A vacuum magnetic dichroïsm is on the other hand predicted from real axions and alps. A direct probe of axions and alps is the photon regeneration giving rise to a light shining through a wall (lsw), which is based on the combination of the transparency of these particles to photons barriers and the magnetic field induced quantum oscillations of these particles with photons associated to a two-photons vertex. Chameleons can show similar mixing to photons under magnetic field but strongly interact with matter. As a matter of fact, its mass strongly increase in the presence of the local environment in matter and this property can be used to imprison chameleons in a jar transparent to photons and detect them as an afterglow resulting from conversions back to photons under magnetic field, leading to a vacuum magnetophosphorescence.
OSQAR experiment at CERN (see the OSQAR website) is at the forefront of this low energy of particle physics. It combines the simultaneous use of high magnetic field with laser beams in distinct experiments. In a first one it aims at measuring vacuum magnetic birefringence and dichroïsm. In a second one it uses the light shining through a wall method for direct detection of axions and alsp. In a third one it will search for chameleon from measurements of vacuum magnetophosphorescence. The interest of these experiments extend much beyond particle physics, since axions and alps are serious dark matter candidates whereas chameleons are predicted from a quintessence accounting for dark energy. The particles might furthermore explain a number of astrophysical puzzles (transparency of universe to high energy photons, anomalous white dwarf cooling, … )
OSQAR is an international collaboration , which in 2014 was composed by 28 members from 12 Institutes from Czech Republic, France, Germany, Poland, and CERN. OSQAR is developed at CERN. It uses two LHC dipole magnets on which precision optics are implemented. Only one permanent member of the team is involved so far : Rafik Ballou.
 Search for Weakly Interacting Sub-eV Particles with the OSQAR Laser-based Experiment : Results and Perspectives, P. Pugnat, R. Ballou, M. Schott, T. Husek, M. Sulc, G. Deferne, L. Duvillaret, M. Finger Jr., M. Finger, L. Flekova, J. Hosek, V. Jary, R. Jost, M. Kral, S. Kunc, K. Macuchova, K. A. Meissner, J. Morville, D. Romanini, A. Siemko, M. Slunecka, G. Vitrant, J. Zicha, Eur. Phys. J. C 74 (2014) 3027 [arXiv,EurPhysJC]
 Latest Results of the OSQAR Photon Regeneration Experiment for Axion-Like Particle Search, R. Ballou, G. Deferne, L. Duvillaret, M. Finger Jr., M. Finger, L. Flekova, J. Hosek, T. Husek, V.Jary, R. Jost, M. Kral, S. Kunc, K. Macuchova, K. A. Meissner, J. Morville, P. Pugnat, D. Romanini, M. Schott, A. Siemko, M. Slunecka, M. Sulc, G. Vitrant, C.Weinsheimer, J. Zicha, Proceedings of the 10th Patras Workshop on Axions, WIMPs and WISPs, CERN, Geneva, 29 June- 04 July 2014, [arXiv,WIMP2014]
 Progress of the Laser Based Experiment OSQAR, M. Sulc, P. Pugnat, R. Ballou, G. Deferne, L. Duvillaret, L. Flekova, M. Finger Jr., M. Finger, J. Hosek, T. Husek, R. Jost, M. Kral, S. Kunc, K. Macuchova, K. A. Meissner, J. Morville, D. Romanini, M. Schott, A. Siemko, M. Slunecka, G. Vitrant, J. Zicha, Proc. of the 9th Patras Workshop on Axions, WIMPs and WISPs, Mainz, Germany, 23 - 28 June 2013, [HAL,WIMP2013]
 Axion search by laser-based experiment OSQAR, M. Sulc, P.Pugnat, R.Ballou, G.Deferne, L.Duvillaret, L.Flekova, M.Finger Jr., M.Finger, J. Hosek, T.Husek, R.Jost, M.Kral, S.Kunc, K.Macuchova, K.A.Meissner, J.Morville, D. Romanini, M.Schott , A.Siemko, M.Slunecka, G.Vitrant, J.Zicha, 12th Pisa Meeting on Advanced Detectors, Isola d’Elba, (Italy, May 20 – 26 2012), Nuclear Instruments and Methods in Physics Research Section A (NIM A) : Accelerators, Spectrometers, Detectors and Associated Equipment, Vol. 718 (2013) pp 530-532 [HAL,NIMA]