Ferroelectric domain engineering with femtosecond pulses of different wavelengths

Direct femtosecond laser writing of ferroelectric domain structures has been an indispensable technique for engineering the second-order optical nonlinearity of materials in three dimensions. It utilizes localized thermoelectric field motivated by nonlinear absorption at the position of laser focus to manipulate domains. However, the impact of laser wavelengths, which is pivotal in nonlinear absorption, on the inverted domains is still sketchy. Herein, the light-induced ferroelectric domain inversion is experimentally studied. It is shown that the domain inversions can be achieved over a broad spectral range, but the optical threshold for domain inversion varies dramatically with the laser wavelength, which can be explained by considering the physical mechanism of femtosecond laser poling and nonlinear absorption properties of the crystal. Meanwhile, the effects of other laser processing parameters are also experimentally investigated. Our findings are useful to guide the fabrication of high-performance optical and electronic devices based on ferroelectric domains.