On-chip nonvolatile and erasable silicon waveguide filter based on a low-loss phase-change material

Silicon waveguide filters are considered an indispensable component for on-chip optical signal processing, spectrum analysis, and neural networks, where its filtering function is determined after fabrication. Electro-optical tuning or thermo-optical tuning can only slightly change the filter spectrum. We propose a nonvolatile and erasable silicon waveguide filter based on the low-loss phase change material Sb₂Se₃. By depositing Sb₂Se₃ layer on both sides of the silicon waveguide and using the laser irradiation-induced phase transition technique, we can write and erase arbitrary grating structures in real time within the erasable Sb₂Se₃ region (length: 36 µm) to change the optical transmission in the silicon waveguide. Three working states were found in such a filter: the low-loss transmission state, the Bragg reflection state, and the Fabry-Pérot cavity resonance state, respectively. Meanwhile, the grating period, width, duty cycle, number, and phase shift can be modified online through laser irradiation with low cost, low power consumption and erasable use, which cannot be achieved using current lithography and etching methods. Finally, we set up the phase change laser processing platform and demonstrated the proposed erasable filter. We believe the proposed silicon waveguide filter and its erasable processing method are promising for programmable photonic circuits and quantum circuits.