Ultraviolet photorefraction and the superionic phase transition of α-LiIO3

The photorefractive effect is investigated in nominally pure α-${\mathrm{LiIO}}_3$ crystals within the 333–514.5 nm spectral range. In the temperature range of 180 K–240 K, i.e., the temperature range of the superionic phase transition, a dramatic decrease of the diffraction efficiency by a factor 100 is observed. This can be explained by the formation of an ionic complementary grating having an activation energy for thermal erasure of 0.32±0.03 eV. Thermal fixing can be achieved by holographic recording at temperatures below about 180 K, developing the complementary grating at room temperatures, and finally recovering the complementary grating below 180 K. In contrast to the assumptions made for the thermal fixing process in other crystals, e.g., ${\mathrm{LiNbO}}_3$, the mobile ionic species in α-${\mathrm{LiIO}}_3$ are mainly lithium ions. © 1996 The American Physical Society.