Periodically poled magnesium-doped lithium niobate (LiNbO3) or PPMgLN is a commonly used crystal for laser frequency conversion using the quasi-phase-matching technique due to its high nonlinear coefficient and high-power optical-damage resistance for visible wavelengths. However, its high distribution coefficient and threshold for magnesium-ion concentration makes it difficult to grow high-quality crystals of this type. But a new near-stoichiometric zirconium-doped LiNbO3 (Zr:NSLN) crystal fabricated by researchers at Nankai University (Tianjin, China) has much lower distribution coefficients and greater damage resistance for both visible and ultraviolet (UV) wavelengths.
Grown by the Czochralski method along the c-axis and fabricated by the vapor-transport equilibrium technique, Zr:NSLN crystals with a variety of zirconium-oxide (ZrO2) doping concentrations were tested to determine UV-visible absorption parameters. Optical-damage-resistance values for Zr:NSLN reached 80 GW/cm2 for 532 nm pulsed-laser light and 20 MW/cm2 for 514.5 nm continuous-wave laser light (comparable to PPMgLN), but reached 120 kW/cm2 at 351 nm—far better than any other LiNbO3-based crystal measured by the research team. Furthermore, the crystal with 0.5 mol% ZrO2 concentration exhibited the highest optical-power resistance; lower-ion-concentration crystals are typically less prone to manufacturing defects. Contact Hongde Liu at [email protected].
