By picosecond spectrometer with two tunable dye lasers, high temperature superconducting (HTSC) (monocrystal Y-Ba-Cu-O with critical temperature Tc equals 87 K) and metal (Ni) thin films have been investigated. A self-diffraction process efficiency (eta) versus biharmonic pumping component detuning (Omega) has been measured at the temperature (Theta) equals 300 and 80 K. It is found that there is a well-defined dip on the dispersion curve (eta) ((Omega) ) for the HTSC films at (Theta) equals 80 K and -10 cm-1 (Omega) -50 cm-1. This region upper limit corresponds to a superconducting energy gap value 2(Delta) . At 10 cm-1 -1, any distinction of the same type is absent. In other respects all obtained dispersion curves are similar. They consist of the central peak ((eta) approximately equals 10-7, (Omega) -1) and wide wings ((eta) approximately equals 10-9, (Omega) 10 cm-1) with the interference structure. Y-Ba-Cu-O film resonances are coincided with the phonon mode frequencies (120, 335, and 580 cm equals -1). It is shown that photoexcitation kinetics (the sample ''darkening'') must consist of some components. A characteristic time of the most ''ultrafast'' component below 5 fs has been estimated and a complex subpicosecond quantum beats presence has been predicted.