Column-Row Addressing of Thermo-Optic Phase Shifters for Controlling Large Silicon Photonic Circuits

Abstract

We demonstrate a time-multiplexed row-column addressing scheme to drive thermo-optic phase shifters in a silicon photonic circuit. By integrating a diode in series with the heater, we can connect N × M heaters in an matrix topology to N row and M column lines. The heaters are digitally driven with pulse-width modulation, and time-multiplexed over different channels. This makes it possible to drive the circuit without digital-to-analog converters, and using only M + N wires. We demonstrate this concept with a 1 × 16 power splitter tree with 15 thermo-optic phase shifters that are controlled in a 3 × 5 matrix, connected through 8 bond pads. This technique is especially useful in silicon photonic circuits with many tuners but limited space for electrical connections.