Ultra-compact nonvolatile phase shifter based on electrically reprogrammable transparent phase change materials

Optical phase shifters constitute the fundamental building blocks that enable programmable photonic integrated circuits (PICs)-the cornerstone of on-chip classical and quantum optical technologies [1, 2] . Thus far, carrier modulation and thermo-optical effect are the chosen phenomena for ultrafast and low-loss phase shifters, respectively; however, the state and information they carry are lost once the power is turned off-they are volatile. The volatility not only compromises energy efficiency due to their demand for constant power supply, but also precludes them from emerging applications such as in-memory computing. To circumvent this limitation, we introduce a phase shifting mechanism that exploits the nonvolatile refractive index modulation upon structural phase transition of Sb2Se3, a bi-state transparent phase change material (PCM). A zero-static power and electrically-driven phase shifter is realized on a CMOS-backend silicon-on-insulator platform, featuring record phase modulation up to 0.09 pi/mu m and a low insertion loss of 0.3 dB/pi, which can be further improved upon streamlined design. Furthermore, we demonstrate phase and extinction ratio trimming of ring resonators and pioneer a one-step partial amorphization scheme to enhance speed and energy efficiency of PCM devices. A diverse cohort of programmable photonic devices is demonstrated based on the ultra-compact PCM phase shifter.

Automated summary

Optical phase shifters are fundamental building blocks for programmable photonic integrated circuits (PICs), but the existing phase shifters are volatile and require constant power supply, limiting their use in certain applications. To overcome this limitation, researchers have introduced a new phase shifting mechanism using a transparent phase change material, which enables zero-static power and electrically-driven phase shifting. This approach improves phase modulation and insertion loss performance, and also allows for additional functionalities such as extinction ratio trimming and speed enhancement.