  The photon energy dependence of optical Cooper pair breaking rate (CPBR) is
studied for compressibly strained La1.85Sr0.15CuO4 (LSCO) films and
YBa2Cu2.92Zn0.08O7-delta (YBCZO) thin films, and compared to that in
YBa2Cu3O7-delta (YBCO). Unlike in the case of YBCO, the CPBR for LSCO does not
show obvious photon energy dependence. In YBCZO the CPBR shows strong photon
energy dependence similar to YBCO, but with a red shift in the peak position.
Analysis of these results strongly favours a physical picture based on
electronic phase separation in high Tc superconductivity.
