Modification of lithium niobate crystals using vapour phase transport equilibration technique

The vapour phase transport equilibration (VTE) technique was used to improve the homogeneity of LiNbO3 substrates; the process parameters were studied and refined. The cause of cracks after short-time VTE treatment was analyzed using the X-ray double crystal diffraction method. The material homogeneity after VTE treatment was studied systematically. Secondary ion mass spectroscopy showed that VTE-processed LiNbO3 possesses good homogeneity and uniformity. The OH absorption spectrum exhibits a single band peaking at 3466 cm−1 after VTE treatment. The second harmonic generation peak is sharp and exhibits almost no positional variation for the VTE-processed samples, showing an excellent homogeneity with an Li2,O variation of much less than 0.01 mol.%. The experimental results show that the samples after suitable VTE treatment meet the homogeneity requirements of substrates for integrated optics.