Optical neural networks (ONNs), enabling low latency and high parallel data processing without electromagnetic interference, have become a viable player for fast and energy-efficient processing and calculation to meet the increasing demand for hash rate. Photonic memories employing nonvolatile phase-change materials could achieve zero static power consumption, low thermal cross talk, large-scale, and high-energy-efficient photonic neural networks. Nevertheless, the switching speed and dynamic energy consumption of phase-change material-based photonic memories make them inapplicable for in situ training. Here, by integrating a patch of phase change thin film with a PIN-diode-embedded microring resonator, a bifunctional photonic memory enabling both 5-bit storage and nanoseconds volatile modulation was demonstrated. For the first time, a concept is presented for electrically programmable phase-change material-driven photonic memory integrated with nanosecond modulation to allow fast in situ training and zero static power consumption data processing in ONNs. ONNs with an optical convolution kernel constructed by our photonic memory theoretically achieved an accuracy of predictions higher than 95% when tested by the MNIST handwritten digit database. This provides a feasible solution to constructing large-scale nonvolatile ONNs with high-speed in situ training capability.

信息技术的发展使得通讯波段集成光子技术在过去的几十年中被广泛重视并取得了突出进展，目前已走向商业化，这一技术的发展也激发了人们对于中红外波段（2~20 μm）片上光子集成的兴趣。中红外波段在空间光通信、热成像、物质探测分析等关乎国家发展、**安全、民生改善等技术领域具有重要的应用前景。利用半导体工艺实现中红外光电子系统芯片小型化在尺寸、功耗以及大规模量产部署具有重大优势。因此，发展中红外片上集成光电子技术具有重大意义。文中主要针对于中红外波段片上集成的一些关键基础器件（如：调制器、探测器）的突破性进展及代表性工作进行了回顾；对各器件的种类、性能、参数及加工手段分别进行了较为全面的调研与比较；同时，也对器件的发展进程、亟待解决的问题以及对未来的展望进行了总结。

Optical filters are essential parts of advanced optical communication and sensing systems. Among them, the ones with an ultrawide free spectral range (FSR) are especially critical. They are promising to provide access to numerous wavelength channels highly desired for large-capacity optical transmission and multipoint multiparameter sensing. Present schemes for wide-FSR filters either suffer from limited cavity length or poor fabrication tolerance or impose an additional active-tuning control requirement. We theoretically and experimentally demonstrate a filter that features FSR-free operation capability, subnanometer optical bandwidth, and acceptable fabrication tolerance. Only one single deep dip within a record-large waveband (S+C+L band) is observed by appropriately designing a side-coupled Bragg-grating-assisted Fabry–Perot filter, which has been applied as the basic sensing unit for both the refractive index and temperature measurement. Five such basic units are also cascaded in series to demonstrate a multichannel filter. This work provides a new insight to design FSR-free filters and opens up a possibility of flexible large-capacity integration using more wavelength channels, which will greatly advance integrated photonics in optical communication and sensing.