Nature of high temperature states in HxLi1-xMO3 (M=Nb, Ta)

Proton exchanged waveguide layers on lithium niobate and lithium tantalate substrates are the basis for single polarization integrated optic devices. It was shown, that the high temperature, metastable at room conditions, phases exist upon ∼50-70 °C in H_xLi_1-xMO₃ (M=Nb, Ta) in all equilibrium at room condition rhombohedral phases. Considering the operating modulators temperature of high frequency (∼60 °C), the formation of high temperature phase could occur due to using the device, and this will entail long time drift of optical parameters of system. In this work the correlation between calculated electron structures of low doped H_xLi_1-xMO₃ (M=Nb, Ta) was shown with experimental data appurtenant to high temperature decay process. It was supposed, that the existence of high temperature phases bound up with possibility of removing of protons to unstable position in crystal lattice. The triple well electronic structure of high doped H_xLi_1-xMO₃ (M=Nb, Ta) was assumed.