Semiconductor saturable absorption mirror (SESAM) is the most commonly-used passive mode-locking device in ultrafast laser technology. Owing to its advantages of self-starting, low insertion loss, high integration, and flexible design, SESAM has a wide range of applications and excellent commercial prospects. This study introduces the mode-locking principle and current development status of SESAM and summarizes the current epitaxial structure, growth mode, and parameter performance of SESAM. It also provides a detailed description of its latest progress in mode-locking in solid-state, semiconductor, and fiber lasers. Moreover, the performance characteristics and future-development direction of various types of mode-locked lasers are presented.