Optical and electro-optical properties of sol-gel derived ferroelectric thin films

Ferroelectric (FE) thin films have been widely studied, especially for their electrical and ferroelectric properties, such as nonvolatile FE memory and ultrahigh density DRAMs. FE films also give rise to a variety of interesting and unique optical applications, such as electro-optic switches, passive and active waveguides, second harmonic generation, optical data storage, optical diodes and photovoltaic devices. Their dielectric properties have been extensively optimized but the optical and electro-optical aspects have not been satisfactorily explored. This paper will review the latest advances in the optical and electro-optical properties of FE films, highlighted by data obtained from our laboratories. Optical (refractive index and waveguiding loss) and electro-optical (linear (r₃₃) and quadratic (R₃₃) electro-optic coefficients) properties will be presented. Optimization of these properties by precise tailoring of chemistry, processing conditions and microstructure is discussed. Low optical loss, i.e., < 2 dB/cm and an exceptionally high r₃₃ value of 315pm/V from PLZT films were obtained.