The Property Of Femtosecond Laser Simultaneous Spatial And Temporal Focusing And Its Application In Micro/Nano Fabrication

Femtosecond laser is a kind of pulse laser with ultra-short duration and ultra-high peak power, which is widely used in many areas. The simultaneous spatial and temporal focusing(SSTF) is a kind of focusing method of broadband laser. A new focusing dimension and a new controllable dimension are introduced by SSTF. Many news features are applied in fabrication field by combining the femtosecond laser and simultaneous spatial and temporal focusing. In recent years, the femtosecond laser simultaneous spatial and temporal focusing processing method attracted more and more attention. A lot of problems can be avoided by this method, such as self-focusing in processing with low NA lens; the elliptical section in micro-channel processing and low resolution along wave vector in 3-D rapid prototyping. These special effects make the femtosecond laser simultaneous spatial and temporal focusing very potentially useful in many areas including micro-channel processing, 3-D rapid prototyping, high scattering material processing, the high speed dynamic control in processing and so on. However, the optic characteristics of femtosecond laser simultaneous spatial and temporal focusing are not clearly understood and there are remain many scientific and technological problems to solve.In this paper, the static and dynamic characteristics of the focal spot in femtosecond laser and simultaneous spatial and temporal focusing are studied, the influence of which in processing were also analyzed by experiments. The main contents of this paper are as follows:1. A general algorithms of ultra-fast laser reshaping and focusing was presented byintroducing the frequency into light field shaping. The focusing spot properties ofvarious amplitude shaping, phase shaping and polarization shaping are analyzedby theoretical calculation.2. The static and dynamic characteristics of SSTF were analyzed by theoreticalcalculation. In static aspects, there is a smaller size along wave vector of thefocusing spot of SSTF. In dynamic aspects, the focal spot is shifting with anultra-fast speed during the pulse, which provides a mothed to control manyultrafast process. By combination with other focal spot control method,multi-spot movement, varies spot movement and discontinuous movement wererealized. 3. The influence of static and dynamic characteristics of SSTF in fabrication werestudied in experiment. In static aspects, the air ionization state and micro-channelprocessing with SSTF were studied. In dynamic aspects, the changing inprocessing areas and micro structure caused by the fast movement of focal spotwere studied.