  For YBa_2Cu_3O_{6+\delta} and Bi_2Sr_2CaCu_2O_8 superconductors, electronic
Raman scattering from high- and low-energy excitations has been studied in
relation to the hole doping level, temperature, and energy of the incident
photons. For underdoped superconductors, it is concluded that short range
antiferromagnetic (AF) correlations persist with hole doping and doped single
holes are incoherent in the AF environment. Above the superconducting (SC)
transition temperature T_c the system exhibits a sharp Raman resonance of B_1g
symmetry and about 75 meV energy and a pseudogap for electron-hole excitations
below 75 meV, a manifestation of a partially coherent state forming from doped
incoherent quasi-particles. The occupancy of the coherent state increases with
cooling until phase ordering at T_c produces a global SC state.
