Silicon Integrated Waveguide Modulator Based on a Three-Terminal Device Structure

Abstract

We report a comprehensive study on the silicon optical waveguide modulators fabricated with and without the isolation trenches based on a modified structure of junction field-effect transistor (JFET). The particular emphases are dedicated to elucidating the influences of various device dimensions on their corresponding modulation efficiencies and frequency responses. Specifically, the enhancement in the modulation depth of the devices was clearly observed as their rib waveguide widths or modulation lengths became respectively wider or longer. In fact, a nearly 100% modulation index could be achieved with a bias voltage as low as 4 V. Furthermore, the modulation efficiency of the devices was evidently improved with a substantial degree by adopting a three-terminal JFET structure for signal modulation; the lowest rise and fall times obtained were 250 and 400 µs, respectively. Finally, adding trenches to each side of the rib seemed to impede the carriers flow, thereby slowing down the carrier injection or accumulation speed during the actual device operation.