Abstract
Analysis and experiment were done on a light intensity modulator using guided-to-radiation mode coupling in a graded-index waveguide; high-efficiency modulation was demonstrated in the Nb-diffused Z-cut LiTaO3 waveguide. In the analysis, we developed a numerical integration method for modal analysis of a graded-index waveguide and showed that more than 50-dB/cm modulation efficiency is obtainable in a Nb-diffused Z-cut LiTaO3 waveguide by choosing an appropriate amount and depth of Nb diffusion. After studying the characteristics of Nb diffusion into Z-cut LiTaO3 we fabricated slab and channel waveguide modulators. The measured modulation depth was 28 dB/5 mm at 400 V across 50-μm spaced electrodes in the slab modulator and was 19 dB/5 mm at 70 V across 10-μm spaced electrodes in the channel modulator.
© 1986 Optical Society of America
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