Research Progress of External Cavity Diode Lasers for Portable Quantum Precision Measurement

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.