Research On Ultrafast Laser Filament-induced Air Laser

Ultra-fast laser filamentation phenomenon has drawn much attention in the application fields of environment monitoring and space exploration recently.The ultra-fast laser filamentation phenomenon contains fruitful physical processes,such as the dynamic interplay between the self-focusing caused by the optical Kerr effect and the plasma defocusing,intensity clamping,self-phase modulation,self-steepening,super-continuum generation,etc.It has shown great value for terahertz wave generation,pulse compression,lightning control,etc.Besides,ultra-fast laser filamentation induced air laser has become a new research direction recently and displayed great potential in the field of atmospheric remote-sensing.The concrete research contents are as follows:1.The multiple filaments are usually randomly distributed during ultra-fast laser filamentation,so we proposed to control of multiple filaments by axicon.Firstly,we studied property of the quasi-Bessel beam created by the axicon during linear propagation in air.Then we controlled the multiple filaments by axicon through the experiments and the theoretical simulation.It is found that we can control of multiple filaments by the axicon.Meanwhile,the length of filaments can be increased.The results are valuable for the atmospheric pollution remote-sensing purpose.Besides,the laser pulse self-compression phenomenon has been observed,which could be used to generate attosecond pulse and high order harmonics.2.The backscattered fluorescence and the side direction fluorescence of nitrogen from filaments generated by intense ultra-fast laser pulses propagating in air is studied,Using optical devices such as lenses and phase plates,the backscattered fluorescence and the side direction fluorescence from N,ions and molecules showed an exponential increase with increasing filament length.And the fluorescence intensity is amplified in the backward direction through amplified spontaneous emission,which is useful for achieve the purpose of remote-sensing.3.The laser induced breakdown spectroscopy(LIBS)is a promising technique for analyzing elements of samples recently.It has many advantages,such as rapid and in-situ analysis,online analysis and simultaneous multi-element detection.It can be used to analyze solid,liquid and gas samples.We demonstrated the feasibility of ultra-fast laser filament-induced breakdown spectroscopy for probing the lines by recording the fingerprint spectra of copper,aluminum zinc alloy,NaCl aerosol and absolute ethyl alcohol aerosol,etc.The ultra-fast laser filament-induced breakdown spectroscopy is helpful to realize multi-component analysis of atmospheric pollutants.