LiTaO3

LiTaO3, or lithium tantalate, is a ferroelectric, piezoelectric, and nonlinear optical single crystal widely used in photonics and optoelectronics. Its chemical formula is LiTaO3, and it is isostructural with LiNbO3, belonging to the trigonal crystal system and the R3c space group. The crystal exhibits a strong second-order nonlinear optical response and notable electro-optic effects, making it valuable for frequency conversion and modulation.

Two common forms appear in practice: congruent LiTaO3, which is lithium-deficient, and stoichiometric LiTaO3. The congruent variant often contains intrinsic defects that influence optical properties, while stoichiometric crystals have lower defect densities. Magnesium oxide doping (MgO:LiTaO3) is widely used to reduce photorefractive damage and improve damage resistance in high-intensity applications.

Growth and fabrication: LiTaO3 is grown from melt by techniques such as the Czochralski method and can be produced as bulk crystals, wafers, or integrated into devices. It is also routinely periodically poled to create quasi-phase-matching structures, enabling efficient nonlinear interactions in devices such as frequency doublers and optical parametric oscillators.

Optical properties and applications: The material is transparent from the near-ultraviolet through the mid-infrared, typically covering wavelengths from roughly 350 nm to several micrometers. It supports second-harmonic generation, sum-frequency generation, and electro-optic modulation. Periodically poled LiTaO3 and related periodically poled structures are widely used to engineer phase matching in lasers, waveguides, and integrated optics for telecommunications and sensing.

Photorefractive effects can occur at visible wavelengths, potentially limiting high-intensity beam performance. These effects are mitigated by MgO doping and careful device design.