The effects of boule to boule compositional variations on the properties of LiNbO3 electro-optic devices—an interpretation from defect chemistry studies

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Abstract
Switches and modulators fabricated on LiNbO3 substrates will be important components of lightwave telecommunications networks. An important aspect of the introduction of this technology into manufacture is the understanding and control of device variability. There are many reasons for this variability. In studying the defect chemistry of LiNbO3, we have found a major cause to be boule-to-boule compositional variations. A 0.2 mole% change in Li2O content translates into a 20% change in Ti diffusivity near the congruent composition (48.45 mole% Li2O). Calculations show that 0.5 μm changes in width and depth of optical modes for TM polarization result. Changes of this magnitude would drastically alter optical properties of directional coupler devices.