On‐Chip Optical Spectrally Sliced Synthesis for Ultra‐High‐Speed Signals

Abstract Broadband optical signal generation is fundamental across a wide range of application areas including high‐speed optical communication, microwave photonics, and metrology. Traditionally, high baud‐rate signal generation has been constrained by the “electronic bottleneck” of complementary metal‐oxide‐semiconductor (CMOS) digital‐to‐analog converters (DAC), making it challenging to scale up the symbol rate to 200 Gbaud and beyond. Here, for the first time, the generation of ultra‐broadband optical signals are demonstrated via spectrally‐sliced synthesis integrated on a thin‐film lithium niobate (TFLN) platform. This spectrally sliced transmitter can significantly scale up the symbol rate using existing DACs with limited bandwidth and sampling rates. The on‐chip integration in the TFLN platform not only offers a higher information density compared to bulk discrete components, but also greatly enhances the stability and performance of synthesized high baud rate optical signals through accurate phase matching. By synthesizing two spectral slices on‐chip and using DAC sampling rates of only 128 GSa s −1 , Nyquist single‐carrier signals are generated with baud rates and line rates up to 240 Gbaud and 2 Tbit/s, respectively. The high‐performance and compact optical transmitter offers a new paradigm in scalable bandwidth, unlocking unprecedented capacity for massive artificial intelligence (AI) clusters.