MicroRaman and photorefractivity study of hafnium-doped lithium niobate crystals

We present an investigation of the properties of HfO2-doped lithium niobate crystals, in view of their possible utilization as low-photorefractivity crystals for wavelength converters operating at room temperature. MicroRaman measurements indicate that the linewidth of a specific mode can be used as a local indicator of crystal composition, and show that the grown crystals present very good uniformity. The mechanism by which the photorefractivity is strongly reduced when the HfO2 concentration is above 4mol% is studied by combining measurements of birefringence variation, under green-light illumination, with electrical phototransport data