Broadband Nonvolatile Electrically Controlled Programmable Units in Silicon Photonics

Programmable photonic integrated circuits (PICs) have recently gained significant interest because of their potential in creating next-generation technologies ranging from artificial neural networks and microwave photonics to quantum information processing. The fundamental building block of such programmable PICs is a 2 × 2 programmable unit, traditionally controlled by the thermo-optic or free-carrier dispersion. However, these implementations are power-hungry and volatile and have a large footprint (typically >100 μm). Therefore, a truly “set-and-forget”-type 2 × 2 programmable unit with zero static power consumption is highly desirable for large-scale PICs. Here, we report a broadband nonvolatile electrically controlled 2 × 2 programmable unit in silicon photonics based on the phase-change material Ge2Sb2Te5. The directional coupler-type programmable unit exhibits a compact coupling length (64 μm), small insertion loss (∼2 dB), and minimal crosstalk (