大功率GHz重复频率飞秒光纤激光技术及前沿应用

High-power GHz repetition rate femtosecond fiber laser technology and advanced applications

与kHz~MHz重复频率飞秒激光相比,GHz重复频率飞秒激光具有更大的频率间隔、更易获得高平均功率,是光谱学、生物光子学、微波光子学、精密加工等基础研究与工业应用领域的崭新工具.光纤型飞秒激光在光束质量、紧凑性、鲁棒性等方面具有先天优势,是大功率GHz重复频率飞秒激光的重要发展方向,有望拓展激发超快激光在尖端领域应用,支撑核心工业、生命医学、航空航天等领域持续创新.本文从大功率GHz重复频率飞秒光纤激光器的技术难点、最新进展、前沿应用等方面进行综述,并展望未来发展前景.

Gigahertz(GHz)repetition rate femtosecond(fs)lasers,in contrast to the lower repetition rate,like kilohertz(kHz)to megahertz(MHz),present superior frequency spacing and accessibility to achieve high average power.Consequently,they are emerging as powerful tools for both fundamental research and industrial applications,such as spectroscopy,biophotonics,microwave,and precision machining.It is also worth noting that fiber lasers have inherent advantages in beam quality,compactness,and thermal management,which contribute to the average power scaling of GHz laser.The development of high-power GHz fs lasers pushes the application of ultrafast lasers in cutting-edge fields such as micronano material processing,military defense,life sciences and aerospace,which make it an attractive alternative to conventional solid-state lasers.Despite the above advantages,its capability of all fiberizing and scalability of peak power is technically challenging due to the nonlinear effects of optical fibers(particularly in single-mode operation).To this end,many technologies have been proposed,including the chirped pulse amplification(CPA)technology and the nonlinear chirped pulse amplification(NCPA)technology.In addition,Mourou et al.proposed the International Coherent Amplification Network Project(ICAN)in 2006.The major project aims to use tens of thousands of fiber laser arrays to achieve ultra-strong laser pulses with single pulse energy greater than 10 J,repetition frequency greater than 10 kHz and pulse width of 100–200 fs,which will be applied to the exploration of a new generation of particle accelerator driver.The realization of this major project depends on the development of CPA and the spatial and temporal coherent pulse combination,so that the high-power GHz repetition rate femtosecond fiber laser has gradually received attention.It is worth noting that at the same average power,the use of GHz repetition rate pulse can significantly reduce the nonlinear pulse distortion during amplification.Due to the short interval time of pulses,the spatial and temporal coherent pulse combination of high-power GHz repetition rate ultrafast laser also shows great potential in the generation of high energy and ultra-narrow pulses.The GHz ultrafast laser has a high application value.In the field of precision machining,on one hand,the short action time between the ultra-short pulse and the material can reduce the collateral damage from heat accumulation at higher laser powers;on the other hand,the GHz burst mode laser makes ablation cooling possible,which can significantly improve the processing efficiency and quality.In the optical frequency comb,the high-power GHz repetition rate fs laser has the higher average power for each comb,which is a new tool in the fields of spectral analysis,optical communication,astronomy,laser ranging,and so on.In terms of biological imaging,with the advantage of high imaging speed,the ultra-fast laser with GHz repetition rate can significantly reduce the influence of the photobleaching effect and phototoxicity effect.In this paper,we provide a comprehensive review of technological challenges,latest advancements,frontier applications,and prospects of high-power GHz repetition rate fs fiber lasers.