Research On The Generation Of Femtosecond Laser Sub-pulse Trains With Birefringent Crystals And It’s Applications

Combining femtosecond laser and holographic imaging, pulsed digital holography is used to recording the intensity and phase information of the object field to detect superfast transient process. In the holography recording process, a single pulse will be divided into a sequence of collinear object sub-pulses with time delay on the order of femtosecond to picosecond magnitude and a sequence of reference light with the same time delay and different angles. The two pulse sequences interfere on the plate, and a hologram is formed. The object pulse sequence with the sub-pulses of equal energy, equal interval, low chirp and transmitting in the same direction is generated. Similarly, the reference pulse sequence with the same interval and energy of pulses as object sub-pulses and different directions of propagation is generated. The pulse width, interval, power and quantity of sub-pulse is associated with the detective accuracy. Above all, ultra-short pulse splitting technology is a key role in the pulse digital holographic system.The femtosecond laser micro-nano processing is another application direction of the ultra-short pulse splitting technology. Although the traditional micro-machining technology with single point scanning has become increasingly mature, the inefficient process still leads to a time-consuming processing of one piece of structure, being the main barrier of industrial development of femtosecond laser processing technology. Therefore, the method of parallel processing has profound value and meaning to improve processing efficiency. To do all that effectively, the process of ultra-short pulse splitting has to be completed first. The method of generation of sub-pulses with birefringent crystals has the advantage of higher accuracy.This article comes from the Basic Research Project on Scientific Instruments of National Natural Science Foundation of China(61227010) and the main contents are as follow:First, Two application directions of femtosecond laser, pulsed digital holography and femtosecond parallel processing, and their research status at home and abroad will be introduced in this paper. And the birefringence phenomenon in the birefringent crystals will be discussed.Secondly, The method of generation of collinear femtosecond laser sub-pulse trains with birefringent crystals is proposed; The optical pathway diagram of object light beam system is designed based on the research of birefringence.Finally, The splitting method of spatial parallel pulse trains is proposed, with which the application efficiency was analyzed in the field of pulsed digital holography and parallel processing.