Towards High Resolution Trimming of Silicon Photonic Waveguides

Methods for high resolution phase trimming of silicon Mach–Zehnder interferometers via the electrical annealing of amorphized waveguide sections are presented. A high resolution of phase change is necessary to accurately trim the performance of individual devices to correct fabrication errors and when scaling to large programmable photonic circuits. On‐chip microheaters positioned above amorphous waveguide sections are driven by short voltage pulses, causing a degree of recrystallization, controllably changing the material's refractive index. An average resolution of phase change per voltage pulse of 0.0007π is demonstrated if an adaptive method is employed, where the voltage step between successive pulses is set to be dependent on the average phase change brought about by the previous three voltage pulses.