Generation, optimization, and application of ultrashort femtosecond pulse in mode-locked fiber lasers

Ultrafast femtosecond mode-locked fiber laser plays an indispensable role in medical imaging, space ranging, ophthalmology, terahertz spectroscopy, material micromachining, and so on. It’s not only an important tool for people to explore the world, but also a pillar field of laser technology. This review present the generation of femtosecond pulses in ultrafast mode-locked fiber lasers using active, passive, hybrid mode-locking techniques, the emphasis is given to passively mode-locked fiber lasers. In terms of the optimization of femtosecond pulses, we introduce the external compression technique to obtain shorter pulse width, chirped pulse amplification technique to increase pulse energy and obtain high energy femtosecond pulses at the practical band. Furthermore, the coherent beam combination and divided pulse amplification technique to further boost pulse energy are summarized. At the end of this review, we present a detailed overview of the applications of femtosecond pulses including the generation of supercontinuum and tunable femtosecond pulses, and some practical applications. Several perspectives and research directions of femtosecond pulses are also addressed.