Applications of Single-Frequency Semiconductor Lasers

Semiconductor lasers have been widely used in variety of applications, becoming one of the most widely used members of the laser family. The single-frequency semiconductor laser plays more and more important roles in the fields of advanced sciences and technologies in recent years. This chapter introduces four of the typical applications. Section 9.1 introduces the atomic physics and related technologies, especially the laser cooling of atoms and the atomic clock. Section 9.2 is engaged in the development of optical communications, including brief reviews of ordinary fiber communications, coherent optical communications, the microwave photonics, and the free-space communications. Section 9.3 is devoted to the metrology and sensing, including interferometry, optical fiber sensors, and laser spectroscopy. The optical radar, i.e., lidar, and the synthetic aperture lidar are briefly introduced in Sect. 9.4. Each of the topics involves its own detailed theories and technologies; the introductions here give just qualitative descriptions and simplified explanations.