Abstract

Acoustic effects can degrade the performance of LiNbO₃ integrated-optical modulators at frequencies below a few hundred MHz. Acoustic problems have been reported in traveling-wave modulators¹ and in lumped-element modulators using both baseband² and resonant³ drive circuits. The most serious problem is the appearance of ripples in the frequency response owing to acoustic resonances, as shown in Fig. 1. These are typically sharp (as little as 100 kHz wide) and are polarization dependent. Acoustic interactions also cause frequency-dependent changes in the modulator electrode impedance; this causes problems primarily in resonant-matched devices. Finally, acoustic waves can cause cross talk between modulators on the same substrate. We report here the characterization of acoustic effects and methods for their reduction.

© 1990 Optical Society of America