Photodoping effects by femtosecond pulses in insulating YBa2Cu3O6+x and Nd2CuO4 thin films

We have investigated photodoping effects in insulating YBa2Cu3O6.2 and Nd2CuO4, which are parent materials of high TC superconductors, by means of femtosecond pump-probe spectroscopy. The fast change in the whole absorption spectrum is observed after the irradiation of femtosecond laser pulses. The spectral features of the absorption change are in good agreement with those observed for the doped samples. The photodoping effect on the CuO2 plane by femtosecond laser pulses is discussed for both the hole-doped and electron-doped systems.