LASER-INDUCED OXYGEN CONTROL IN SMALL REGION OF YBA2CU3OY, POLY-CRYSTALS AND SINGLE-CRYSTALS, OBSERVED BY MICROSCOPIC IR REFLECTION

We have studied the oxygenation and deoxygenation induced by laser irr adiation in poly- and single crystals of YBa2Cu3Oy by microscopic IR r eflection. We have observed a dramatic appearance and disappearance of the lattice-phonon modes unique to the insulator phase in accordance with the change of conductivity induced by the irradiation. By this me thod, we could detect the mutual conversion of the phase in an area as small as 0.1 x 0.1 mm(2) without using electrodes, which is suitable for the study of the oxygenation and deoxygenation, particularly betwe en y=similar to 6.2 to y=similar to 6.5. The differences in the conver sion behaviors between single and polycrystals are discussed.