Inverse design for ultra-compact integrated photonics

Ultra-compact photonic integration represents a transformative frontier in optical communication and computing systems, offering unprecedented potential for performance enhancement through extreme device miniaturization. However, balancing high performance with minimal device size remains a formidable challenge. Here, we have developed novel optimization algorithms that improve the design paradigm of compact photonic components, achieving record-breaking miniaturization while maintaining exceptional performance. One critical achievement is the realization of a 12—0.5 μm mode size converter with an extremely short length of 2.43 μm, delivering more than 90% transmission efficiency. Furthermore, we have pushed the boundaries of functional device integration by demonstrating micrometer-scale power splitters and wavelength demultiplexers with extraordinary capabilities. Notably, a particularly innovative device is the three-port circular wavelength demultiplexer, which measures mere 1.8 μm in length and enables versatile signal demultiplexing between any input-output port combinations. The strong integration capabilities of the proposed devices are demonstrated through a multichannel system incorporating an array of 14 functional devices within an effective length of only 15.81 μm, achieving a quite low loss and a wide operation bandwidth. These advancements highlight the superior performance ofultra-compact photonics, accelerating the development ofhigh-density photonic circuits for optical communications.