Raman Studies of Photorefractive Lithium Niobate Single Crystals

A study of Raman spectra of lithium niobate single crystals: stoichiometric, ostensibly pure congruent LiNbO3, and congruent LiNbO3 containing admixture of yttrium is reported. Raman bands observed in spectra excited by visible laser radiation are thoroughly compared to the same bands excited by infrared laser radiation. The broadening of Raman bands excited by radiation of shorter wavelengths is attributed to photo-refraction induced by visible radiation (514 nm) while being absent under infrared radiation (1064 nm). Attributing the effect of photo-refraction to radiation-induced structural changes in the illuminated part of the crystal lattice the authors interpret the observed broadening…