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

Abstract 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 × 2 MZI integrated with a low‐loss phase‐change material Sb 2 Se 3 encapsulated in Al 2 O 3 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 Sb 2 Se 3 ‐based phase shifter. By dividing the Sb 2 Se 3 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.