A Raman study of single-crystal congruent lithium niobate following electric-field repoling

We describe a study of the time dynamics of the spectral position of six major peaks in the Raman spectrum of single-crystal congruent lithium niobate, following the process of electric-field repoling. All of the peaks observed show a small (<1 cm-1) frequency shift after repoling. Two peaks are shifted to higher frequencies while the other four are shifted to lower frequencies. The shift generally recovers over time towards the original value. The 153 cm-1 and 432 cm-1 peaks are seen to recover to their original positions before poling, with time constants of approximately 8 h and 4 h, respectively, whereas the higher frequency peak at 872 cm-1 does not appear to recover at all. The other peaks exhibit incomplete recovery. We compare the measured values of temporal recovery with published relaxation times for internal electric fields, and make an additional comparison with our measured etch-rate data for the -z face of lithium niobate as a function of delay time following repoling.