III-V Monolithic integrated tunable edge-emitting semiconductor laser

Semiconductor lasers have evolved into the cornerstone of modern photonics infrastructure. The transition from fundamental homojunction and heterojunction devices to advanced quantum well architectures has enabled superior characteristics—including high monochromaticity, high collimation, and high power density—thereby driving their deployment in core modern laser technologies. Although silicon-based hybrid tunable lasers have been extensively reviewed recently, monolithic integrated tunable lasers based on pure III–V compounds remain dominant in high-performance applications due to their compact footprint, superior mechanical stability, and the elimination of complex inter-chip coupling processes. This review systematically examines the principles and recent advancements in monolithic integrated tunable lasers. Devices are categorized by their mode selection mechanisms: laser arrays based on DFB architectures, structures based on distributed Bragg reflectors (DBR), and grating-free designs relying on interferometric principles, such as V-coupled cavity and multi-channel interference (MCI) lasers. The physical mechanisms of mode selection and phase control strategies underlying these architectures are thoroughly analyzed. In addition, key challenges that are often overlooked in this field were also discussed, including long-term frequency stability (aging effect), the risk of mode transitions during dynamic tuning, etc. Additionally, the trade-offs between grating-based and grating-free interferometric devices regarding tuning range, linewidth, and fabrication complexity are evaluated, providing a technical roadmap for the development of light sources for next-generation optical communications, light detection and ranging sensing, and high-resolution spectral analysis.