Ferroelectric ceramic light gates operated in a voltage-controlled mode

Plates of lead zirconate-lead titanate ferroelectric ceramic can have 1) low-loss optical transmission in thin, polished sections and 2) uniaxial birefringence dependent upon remanent polarization. These properties are potentially useful in electrically variable optical retarders, modulators, and latching light gates. This paper reports the results of measurements of basic light-gate devices using ferroelectric ceramic plates. A number of characteristics of the devices are reported; e.g., dependence of absolute light phase retardation on ceramic remanent polarization; dependence of ON-OFF ratio on exit aperture, switching pulse duration, and light wavelength; switching speed; and the dc hysteresis characteristic of the dependence of remanent polarization upon applied field. In the past, the use of ferroelectric devices under conditions producing partial switching has been discussed exclusively from the point of view of "charge-limited switching." This paper proposes a new mode of operating ferroelectric ceramic light gates using "voltage-controlled switching." Charge-limited switching results naturally when voltage pulses of short duration are used (appreciable ON-OFF ratios can be obtained from a light gate switched with pulses as short as 10 ns). As a result of the hysteresis in the dc switching characteristic, pulses with durations of the order of milliseconds or longer result in operation of the light gate in a voltage-controlled mode. Practical advantages resulting from this mode of operation are discussed.