Electro-optic analog-to-digital conversion using channel waveguide modulators

Some experimental results on the operation of a lithium niobate modulator in a threshold circuit to simulate a bit channel of an analog-to-digital (A/D) converter are presented. Voltages required for π-radian phase retardation were 1.2 and 3.1 V, respectively, for TE and TM excitation. The periodic dependence of modulator intensity on applied voltage is maintained for phase shifts as large as 24π radians in the TE case, which corresponds to 5.6 bits of precision for an A/D converter.