Topics | Introduction to picosecond lasers

Classification of picosecond lasers

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1. All-solid-state Picosecond Laser

2. Fiber picosecond Laser

3. Semiconductor picosecond laser

Mode-locking and passive mode-locking
When the frequency interval of each oscillation mode in the cavity remains constant and has a certain phase relationship, the laser will output a series of ultra-short pulses with a certain time interval, which is called a mode-locked laser.

The lower limit of the pulse width of the Q-switched pulse is about the order of ns. To continue to obtain narrower pulse widths, passive mode-locking using SESAM is one of the techniques, and the pulse width of mode-locked lasers can be as low as Ps to fs.
At the same time, according to the principle of mode-locking, when the mode-locked laser starts to oscillate, due to mode locking, only the modes satisfying the same phase difference can start to oscillate, and the frequency in the cavity is locked as: f=C/2L. Therefore, once the cavity type of the passive mode-locked laser is determined, the frequency cannot be changed.

All-solid-state picosecond laser

The most basic feature of mode-locked picosecond lasers is that the pulse width is very narrow, which can cause less heat transfer, higher peak power, and shorter interaction time with substances. The mode-locked laser has higher peak power and better processing effect at the same frequency as other lasers; when the peak power is the same as other lasers, the frequency is higher and the processing speed is faster. In special fields, such as the processing of heat-sensitive materials and memory alloys, the shorter the pulse width of the laser, the closer to the stress-free cold working, the smaller the thermal conduction and thermal phase change.



In industry, mode-locked picosecond lasers can achieve high-precision and high-efficiency micro-processing and cutting of various materials (such as mobile phone screen cutting), and have broad application scope and prospects in precision machinery, surface engineering and other fields. In scientific research, it is also widely used in optical communication, time-resolved spectroscopy, laser inertial confinement nuclear fusion, ultra-broad spectral characteristics to promote coherence tomography imaging and biomedical diagnosis.

The high-power semiconductor-pumped picosecond laser has stable performance and adopts water cooling for heat dissipation. It has the characteristics of high average power, narrow pulse width and high repetition frequency. It is widely used in the processing of fine materials, suitable for the processing of various transparent and brittle materials such as sapphire and glass, and also suitable for drilling and cutting of metal thin film materials for lithium batteries.



Fiber picosecond lasers