Non-Volatile Optical Switch Element Enabled by Low-Loss Phase Change Material

Mach-Zehnder interferometers (MZIs) integrated with phase-change materials have attracted great interest due to their low power consumption and ultra-compact size, which are favored for reconfigurable photonic processors. However, they suffer from a low optical extinction ratio and limited switching cycles due to high material loss and poor reversible repeatability caused by material degradation. Here a non-volatile electrically reconfigurable 2 x 2 MZI integrated with a low-loss phase-change material Sb2Se3 encapsulated in Al2O3 layers is demonstrated. The phase change is electrically actuated by a forward-biased silicon p-i-n diode. The switch extinction ratio is more than 20 dB due to the low-loss Sb2Se3-based phase shifter. By dividing the Sb2Se3 patch into small sub-cells to restrict the material reflow, more than 10 000 reversible phase-change cycles and 6-bit multilevel switching states are achieved by programming the electrical pulses. Its non-volatility, high endurance, and fine-tuning capability makes the device promising in large-scale low-power reconfigurable photonic processors.