Ultra‐Compact Topological Photonic Crystal Rainbow Nanolasers Operating in the 1550 nm Telecom Band with Wavelength‐Scale Mode Volumes

Topological rainbow trapping, spatially separating and confining multiple topologically protected light frequencies, offers a prospective scheme for achieving robust multi‐wavelength single‐mode coherent emission within a single nanodevice. Here, ultra‐compact topological photonic crystal rainbow nanolasers operating in the 1550 nm telecom band are experimentally demonstrated. Specifically, rainbow‐like single‐mode emission with a controllable free spectral range and a wavelength‐scale mode volume is presented in a one‐dimensional topological rainbow nanolaser, exhibiting robust rainbow spectral emission across a wide temperature range and a spectral tuning capability of approximately 70 nm. Additionally, an ultra‐compact two‐dimensional topological rainbow nanolaser is demonstrated in an exceptionally small footprint, featuring a broad rainbow spectrum with 64 continuously tuned single‐mode lasing peaks. This work provides a promising approach for realizing robust and nanoscale multi‐wavelength single‐mode coherent emission within a single device, paving the way for numerous potential applications in ultra‐compact high‐throughput data processing systems, including on‐chip wavelength‐division‐multiplexing and optical interconnects.