Electro-optical modulator based on carrier depletion or carrier accumulation in semiconductors with advanced electrode configuration

摘要

An electro-optical modulator (1) is proposed to have two electrodes (33, 35) being part of a transmission line (19) of a first phase modulator and further two electrodes (37, 39) being part of a transmission line (19) of a second phase modulator included in two arm of a Mach-Zehnder-interferometer. Each transmission line (19) comprises a pn-diode (41, 43) or a semiconductor-isolator-semiconductor capacitor. Furthermore, an electrical controller (17) is adapted for applying first electrical high-frequency-modulated voltage signals Sig1(t) between the first and second electrodes (33, 35) and for applying second electrical high-frequency-modulated signals Sig2(t) between the fourth and third electrodes (39, 37). However, a DC component of these signals Sig1(t) and Sig2(t) and a polarity with which these signals are applied to the first and second diodes (41, 43) or to the first and second semiconductor-insulator-semiconductor capacitor principally differ in comparison to conventional approaches in that the electrical controller (17) shall apply signals such that voltages applied to the first and fourth electrodes (33, 39) have substantially a same high-frequency content, and the voltages applied to the second and third electrodes (35, 37) have substantially the same high-frequency content. In such configuration, either the voltages applied to the first and fourth electrodes (33, 39) differ by a constant voltage offset, or, alternatively, the voltages applied to the second and third electrodes (35, 37) differ by a constant voltage offset. Thereby, cross-talk between electrodes and electrical losses as well as device size and fabrication costs may be reduced.