Growth in Electric Field of Domain Created by Femtosecond Laser Irradiation in the Bulk of SBN Crystal

We have studied the evolution of the isolated domains created in the bulk by tightly focused femtosecond near infrared laser irradiation under the action of uniform electric field in strontium barium niobate Sr0.61Ba0.39Nb2O6 single crystals. The samples were cut with a deviation from the polar axis of about 3°. The initial domain structure representing the matrix of domains in the bulk of the single domain sample was created in three steps: (1) thermal depolarization, (2) laser irradiation, (3) removing of the nanodomain structure. Laser irradiation leads to formation the matrix of the spindle-shaped domains surrounded by nanodomains. All created domains were strictly oriented along the direction of the laser beam. It was shown that the application of positive field pulse led to growth in the polar direction of new domains from the deepest ends of the created domains. The average threshold field of new domains appearance and mobility of their growth were extracted. We have created the unique domain shape, which represents two united cylindrical parts in the crystal bulk formed as a result of laser irradiation of the sample with nanodomain structure in the direction deviated from the polar direction and application of the uniform external electric field after removing of nanodomains. The growth direction of the first domain part is governed by orientation of the laser beam, and the second domain part—by orientation of the polar axis. Obtained results are important for developing domain engineering methods in ferroelectrics based on domains nucleation by the focused femtosecond laser irradiation and their growth in homogeneous electric field.