Abstract: Understanding the interplay between the phases present in a high-temperature superconductor (superconducting, pseudogap, strange metal and Fermi-liquid-like) is the key-concept for shining light on the nature of the superconductivity mechanisms in copper-oxide based superconductors. In this seminar I will discuss this physics by studying the photoinduced perturbation of the dielectric function between 0.5 eV and 2.2 eV along with its ultrafast relaxation using a novel broadband pump-probe optical spectroscopy. One of most important novelties of these experiments is the evidence of a photoinduced non-thermal quench of the superconducting order parameter at high pump fluence (50-100 μJ/cm2). These results set the way for studying the interplay between superconducting and pseudogap phases in realtime after the quench of the superconducting state.