Nonvolatile photonic field-programmable coupler array

Programmable photonic networks carry out universal unitary functions by independently operating on the amplitude and phase of guided light. Exploiting the reconfigurability and spatiospectral degrees of freedom of these systems, the majority of state-of-the-art photonics applications, ranging from microwave photonics to photonic computing and optical communication links, can be demonstrated in one unified system. Existing techniques require a large footprint due to weak modulation efficiency, and continuous power dissipation to maintain the configured state. Here, we demonstrate a programmable recirculating mesh unit cell based on the nonvolatile low-loss phase-change material Sb₂Se₃. The demonstrated devices achieve an ultrashort active length (<10 μm, more than 15 times smaller than the current state of the art of competing technologies) and zero static power, in combination with high-extinction switching (>20 dB), broadband operation (>15 nm), and low insertion loss (<2 dB). This work forms the basis for nonvolatile field-programmable coupler arrays (nv-FPCAs) and zero-static power reconfigurable optical interconnects.