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.