EFFECTS OF NONEQUILIBRIUM STRUCTURE AND T EMPERATURE ON PHOTOINDUCED CHANGES IN OPTICAL-TRANSMISSION OF YBA2CU3O6.35 FILM

Sharp (similar to 25%) photoinduced changes in the optical transmissio n of the YBa2Cu3O6,35 film, which are non-linearly dependent on the ir radiation time, are found at low temperatures, T < 125 K, and low ligh t Rows (similar to 10(13) photon/cm(2) . s). The conditions are studie d under which the non-linear changes in transmission transform into a linear law. The analysis of the effect based on correlation between th e optic transition intensity and the changing electron !hole) concentr ation in the CuO2 plane permits the conclusion that (i) the degree of the sample ortho-nonequilibrium is the critical condition for effectiv e photopumping of the carriers under low-dose irradiation at low tempe ratures, (ii) the photopumping enhances the relaxation to the equilibr ium ortho-ordering in the CuOx chains under the condition of Iron-line ar photoinduced changes, (iii) on photodoping with light flows above t he metallization threshold, two channels of the electron transition fr om CuO2 to CuOx are in simultaneous operation - one is for the photoel ectrons and the other is for the electron from the Fermi level of the CuO2 plane. At 125 K the heavily pumped film undergoes a structural or der-disorder transition during which the photopumped electrons (holes) are released as the temperature rises.