Heterogeneously integrated single-mode III–V-on-TFLN lasers enabled by narrowband Bragg gratings

Thin-film lithium niobate (TFLN) has emerged as a compelling platform for photonic integrated circuits. However, the realization of electrically pumped on-chip laser sources remains a critical challenge. In this work, we demonstrate heterogeneously integrated single-mode III-V-on-TFLN lasers employing a narrowband Bragg grating in combination with a Sagnac loop reflector (SLR) to provide wavelength-selective optical feedback. Through precise tailoring of the distributed Bragg reflector (DBR) grating period, controlled lasing wavelength selection in the C-band is achieved. The fabricated devices deliver on-chip output power ~1.15 mW and maintain single-mode emission from near threshold to rollover current, with a side-mode suppression ration exceeding 35 dB in the optimum operation point. These results establish the feasibility of electrically pumped laser sources on the TFLN platform and provide a scalable pathway toward fully integrated TFLN-based transmitters and reconfigurable photonic systems.