My contribution will focus on addressing the difference response of superconducting gaps to photoexcitation with large photon energy (larger than the superconducting gap) and subgap excitation. By studying the ultrafast changes of the reflectivity of optimally doped B2212 to the two kinds of photoexcitation we could on one hand confirm that high photon energy excitations trigger a sudden quench of the superconducting gap , but, more intriguingly, I will show how sub gap excitations can dynamically stabilize the superconductor. In particular, by measuring the divergent timescale of the relaxation , we could experimentally address the critical behavior at Tc and thereby directly accessing the superconducting transition temperature subsequently to photoexcitation. Our measurements reveal an enhancement of the critical temperature Tc up to 2 K following the excitation with a low photon energy pump. The transient stabilization of the superconducting gap is further confirmed by the freezing of the relaxation dynamics for subgap excitation. The evidences are tentatively rationalized in the Eliashberg formalism [3,4], where a transient non-equilibrium depletion of the lowest energy states above the superconducting gap can lead to a transient stabilization of the superconductors. Our results open the way to a bidirectional control of superconducting properties in complex oxides.
 C.Giannetti, M. Capone, D. Fausti, M. Fabrizio, F. Parmigiani, D. Mihailovic, Advances in Physics, 65:2, (2016), 58-238,
 A. Rothwarf and B.N. Taylor, Phys. Rev. Lett. 19 (1967) p. 27.
 G.M. Eliashberg, Sov. Phys.-JETP 11 (1960) p. 696.
 G.M. Eliashberg, Sov. Phys.-JETP 12 (1961) p. 1000.