Abstract
A study is made of electro-optic total-internal-reflection diffraction device modulator electroding. This can cause reflection phase inequalities which can reduce transmission (zero order) and degrade the extinction ratio. Al, Cu, Au, and Cr electrodes are considered and Al/Cr appears the optimum choice for LiNbO3 devices. A practical LiNbO3/Cr device realization is shown to exhibit a 0.6% insertion loss contribution due to this effect and agrees with theory. Analysis shows that a reflection phase mismatch of 16 degrees adds to insertion loss by 2%, but at 28 degrees (mismatch) this addition rises to 6%. An extinction ratio >100:1 was noted.

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