Linear and nonlinear optical properties of Hafnium-doped lithium-niobate crystals

Abstract: Measurements of birefringence, second-harmonic phase-matching conditions, and nonlinear coefficient d(31) are performed for a set of Hafnium-doped congruent lithium niobate ( Hf:cLN) crystals as functions of dopant concentration. The data highlight that the threshold concentration, above which there is a change in the Hf incorporation mechanism, is slightly above 2mol% and that, up to this value of concentration, the efficiency of nonlinear processes is not affected by the dopant insertion. Combining these results with those already present in literature, Hf: cLN crystals appear to be very promising candidates for the development of photorefractivity-free wavelength converters working at room temperature.