Research Progress on Littman Tunable External Cavity Semiconductor Lasers in the Near-infrared Band

In recent years, tunable external cavity semiconductor lasers in the near-infrared band have important application value in fields such as fiber optic communication, spectral analysis, and medicine. This article introduces the basic structure and working principle of a Littman tunable external cavity semiconductor laser. Firstly, the research process of Littman structured tunable semiconductor lasers in the near-infrared band was introduced, from initial experimental exploration to current high-performance lasers; Secondly, this article provides a brief overview of the Littman structure and analyzes its advantages in external cavity lasers, including high output power, good spectral characteristics, and ease of wavelength tuning. This article focuses on the research progress of Littman structure tunable external cavity semiconductor lasers. Explained the epitaxial materials, structures, and key technologies for tuning near-infrared semiconductor lasers. The structure of the semiconductor laser and the design structure of the external cavity involved in this article are of great significance for improving the output power, tuning range, and edge mode suppression ratio of the laser. Tuning technology can achieve faster wavelength tuning and wider tuning range. Finally, this article also discusses the application prospects of Littman tunable external cavity semiconductor lasers in different application fields such as fiber optic communication, spectral analysis, biomedical, and gas detection. In summary, significant progress has been made in the research of tunable semiconductor lasers in the near-infrared band, providing strong support for practical applications. Future research should continue to optimize the performance of tunable semiconductor lasers in the near-infrared band, expand the tuning range, improve output power, and explore applications in new fields.