High photorefractive resistance of Hafnium-doped single-domain and periodically-poled lithium niobate crystals

摘要

Transient and steady-state measurements of photo-induced birefringence variations in single domain and periodically poled lithium niobate (LN) crystals containing different non-photorefractive impurities are presented. The birefringence change is induced by a 532-nm laser beam in the intensity range 0-500 W/cm~2, and is probed by 632.8- and 1523-nm beams. Data were taken at 25 and 50℃. We find that HfO_2 doping is very effective in reducing the photorefraction. This is interesting also because it is known that Hafnium-doped LN crystals can be periodically-poled during growth. The analysis of the rise and decay of the induced birefringence shows that doping considerably increases both the photoconductivity and the dark conductivity of the LN crystals.