Electro-optic behavior of lithium niobate at cryogenic temperatures

The unclamped relative permittivity, ε33T, and the Pockels coefficient, r33T, of congruent lithium niobate at a frequency f = 5760 Hz have been determined at low temperatures (7 K < T < 300 K). A He cryostat setup mounted to one arm of an electronically phase-stabilized Michelson interferometer was utilized for the measurement of r33T. A continuous decrease in both parameters was observed as T → 0 K with limiting values of ε33T≈25.4±0.1 and r33T≈24±0.7pm/V, respectively.