Narrow-linewidth broadband tunable external cavity diode lasers (NBTECDLs), with their broadband tuning range, narrow linewidth, high side-mode suppression ratio (SMSR), and high output power, have become important laser sources in many fields such as optical communication, spectral analysis, wavelength division multiplexing systems, coherent detection, and ultra-high-speed optical interconnection. This paper briefly describes the basic theory of NBTECDLs, introduces NBTECDLs with diffraction grating type, fiber Bragg grating (FBG) type, and waveguide type, and conducts an in-depth analysis on the working principles and performance characteristics of NBTECDLs based on different NBTECDL types. Then, it reviews the latest research progress on Littrow-type, Littman-type, FBG-type, and waveguide-type NBTECDLs in detail and compares and summarizes the characteristics of Littrow-type NBTECDLs, Littman-type NBTECDLs, FBG-type NBTECDLs, and waveguide-type NBTECDLs. Finally, it looks at the structural features, key technologies, optical performance, and application fields of the most cutting-edge research in recent years and summarizes the challenges and future development directions of NBTECDLs.

High-power semiconductor laser diode arrays (LDAs) are pivotal for applications such as optical pumping, industrial manufacturing, and precision measurement, yet they face inherent bottlenecks in balancing high output power, superior beam quality, and stable phase synchronization. The Talbot cavity, leveraging the Talbot self-imaging effect, has emerged as a core external cavity technology to address these challenges, enabling global coupling and passive phase locking of LDAs. This paper systematically reviews the research progress of Talbot cavities in phase-locked LDAs under global coupling. It elaborates on the fundamental principle of Talbot-effect-based phase locking, along with the structural characteristics and working mechanisms of three typical Talbot cavity configurations: conventional Talbot cavities, V-shaped Littrow–Talbot cavities, and monolithic integrated Talbot cavities. Furthermore, it summarizes key experimental advancements of LDAs, covering diverse laser media (e.g., near-infrared, blue, terahertz, and mid-infrared antimonide lasers) and array scales ranging from a few to thousands of emitters, with representative performance metrics including far-field visibility up to 99%, narrowed spectral linewidths achieving 20–50 pm for blue LDA, and output power exceeding 200 W. Numerical simulation progress on supermodel stability and parameter optimization is also discussed. Finally, the current challenges, such as thermal crosstalk and integration complexity, are analyzed, and future prospects involving intelligent control and novel physical mechanisms are outlined. This review aims to provide a comprehensive reference for the further development and practical application of high-brightness phase-locked laser sources.

Tunable external cavity diode lasers (ECDLs) are core light sources for portable quantum precision measurement, offering narrow linewidth, wide tuning range, and high spectral purity. This review systematically summarizes the research progress of ECDLs for portable quantum applications, classifying mainstream configurations into Littrow, Littman, fiber grating, and filter types. The structural principles, performance characteristics, and recent breakthroughs of each type are elaborated, with in-depth analysis of the trade-offs among tuning range, linewidth, side-mode suppression ratio (SMSR), and output power. Key progress in miniaturization and integration is highlighted, focusing on MEMS-driven tuning and silicon waveguide hybrid integration technologies, which address the conflict between performance and portability. Current challenges including mode hopping, thermal stability, and packaging loss are discussed, and future directions such as multi-band extension, isolator-free frequency stabilization, and AI-assisted control are prospected. This work provides a systematic reference for the development of compact, high-performance ECDLs toward field-deployable quantum sensors.

The TECSL has attracted much attention due to its wide tuning range, narrow linewidth, high output power, and excellent SMSR. It holds irreplaceable value in optical communication, spectroscopy analysis, and biomedical applications. The demand for a wide tuning range, high power, narrow linewidth, and a high SMSR has driven the development of high-performance TECSL structures. This paper comprehensively discusses five key TECSL structures: Littrow-type structures, Littman-type structures, filter-type structures, fiber-type structures, and waveguide-type structures, and elaborates on their structures and principles. This paper reviews the research process of different type-structure TECSLs, analyzes the advantages and disadvantages of different external cavity structures, and explores the future development trends of TECSLs. The review shows that the Littrow-type structure TECSL achieved an extremely wide tuning range using diffraction gratings, reaching up to 360 nm. The Littman-type structure TECSL demonstrated excellent spectral purity, achieving an SMSR of 71.03 dB. The filter-type structure TECSL was able to achieve flexible wavelength selection using tunable filters, achieving a linewidth of 570 Hz. The fiber-type structure TECSL has a linewidth of up to 600 Hz. The waveguide-type structure TECSL can achieve a linewidth as low as 0.252 kHz and a tuning range of up to 120.9 nm.