Programmable Non‐Volatile Photonic Analog‐to‐Digital Converter Based on Back‐End‐of‐Line Compatible Phase‐Change Materials

High-performance signal processing and telecommunication systems absolutely necessitate analog-to-digital converters (ADCs) that offer extensive bandwidth, exceptional precision, and minimal power consumption, in order to efficiently convert real-world analog signals into digital signals. While current electronic ADCs are constrained by limitations such as low bandwidth, high jitter noise, susceptibility to electromagnetic interference, and excessive energy consumption, photonic ADCs present promising solutions to overcome these challenges. Here, a programmable photonic ADC is developed by integrating phase-change materials (PCMs) with silicon photonics fabricated using foundry processes. Thanks to the programmability and non-volatile nature of PCMs, 2- and 4-bit photonic ADCs are demonstrated on a single chip, achieving zero energy consumption during the quantization. Through the experimental demonstration of 65-state PCMs, photonic ADCs can attain a resolution of 8-bit, marking a significant milestone as the highest resolution reported to date for ADCs leveraging optical technologies. As a proof of concept, an all-optical analog-to-digital conversion system is demonstrated by integrating 2-bit photonic ADCs with optical sampling using a mode-locked laser (MLL). This system achieves the conversion of a 321 MHz radio frequency (RF) signal at a sampling rate of 40 MS s^-1. The programmable, energy-efficient, and high-speed photonic ADCs represent a significant advancement in the evolution of signal processing systems.