In lasers, the generation of ultrashort pulse lasers is important because pulsed light can be generated by controlling the coherent light waves of the laser, and its time width is beyond the control range of electronic devices. Ultrashort pulse light in a broad sense refers to pulsed light of less than 1ns. In the mid-1960s, scientists conducted experimental research on mode-locked ultrashort pulse light generated by ruby ​​lasers and neodymium-doped lasers of flash lamp pulses. Since then, the generation technology of short pulse light has developed from mode-locked sub-picosecond pulses to femtosecond pulses. In recent years, ultrashort pulse laser technology has become popular, and various tunable ultrashort pulse mode-locked solid-state lasers have been put into practical use since the 1990s. Tunable lasers are photon-terminated lasers whose energy levels are in a vibrationally excited state under the action of the laser, thereby broadening the oscillation frequency band. Typical titanium sapphire lasers operate stably and can achieve ultrashort (shortest about 5fs) pulse light with an average output power of 1W. If a laser crystal doped with ytterbium ions is used, sub-picosecond pulses with higher average output power can be output. Semiconductor lasers have the characteristics of fast relaxation and high-speed modulation of pump (current), so even without mode locking, ultrashort pulse phenomena light in the picosecond region (10-10~10-12 s) can be generated by gain transition.

The recent development of small-scale picosecond and femtosecond pulse lasers has made the development of ultrashort pulse light sources possible. Considering the requirements for ultrashort pulse light sources from the perspective of light utilization, whether to effectively utilize the characteristics of the time domain (ultra-high speed) or to utilize the high peak intensity of concentrated light energy in a short time is the key. Two major research directions. In practical applications, these two directions are closely related. From the above point of view, maximizing the pursuit of light source performance to achieve shorter pulse light and higher peak intensity is the driving force for the development of this technology. In addition, improving the performance of new light sources, promoting the discovered new functions or new phenomena and making them practical; improving the reliability, stability and life of light sources, and reducing costs are also the keys to technological development. In addition to increasing pulse width and pulse energy, improving beam quality is also an extremely important research topic. This has a huge impact on the development of this technology field, just like maximizing the coherence of time and space.

People have accumulated a lot of experience in the development of ultrashort pulse laser technology, such as effectively generating high-intensity pulses in the pulse generation stage and obtaining high-energy pulses as much as possible; various attempts have been made to directly generate high-intensity ultrashort pulses. And research results that contribute to the development of this field have been achieved. However, in the process of generating and using high-intensity pulses, the coherence or waveform, repeatability and reliability of optical pulses are not ideal. Therefore, the high-repetition pulse output and high-magnification method of using mode-locked laser oscillators has become the mainstream. Although the energy of each pulse is small, the pulse generation source can easily obtain pulses with good coherence using a continuous oscillation mode-locked laser.