The Characteristics Of Laser Beam And Pulse Laser When It Propagation In The Turbulent Atmosphere

This paper focused on the characteristics of laser beam transmitted in the turbulent atmosphere. Based on related theory of atmospheric turbulence, transmission characteristics of laser for slant path through atmosphere in consideration of internal and external scales were analyzed. The results show that the scintillation index of laser, spreading and wander fluctuation can easily be affected by the turbulence intensity and external scales. With theory of strong turbulence, the mutual-correlation function of laser beam propagation in the turbulent atmosphere was discussed. According to extended Huygens-Fresnel principle and unified theory for polarization and coherent, the degree of polarization expression for laser beam was deduced. With this expression, the variation rule for degree of polarization in case of 1550nm and 850nm Laser in slant path atmosphere was obtained. The results show that degree of polarization is mainly affected by laser wavelength, the initial degree of polarization, the correlation length of x-axis and y-axis. By using mutual coherence function, the characteristics of second-order statistics of the pulse-wave which transmits through the atmospheric turbulence have been studied, including the coherence time and coherence bandwidth. It is found that they increase with both outer and inner scale, more quickly with the former, while they decrease quickly with increasing of bandwidth and fluctuations of the atmospheric turbulence.This research work can provide somewhat guidance to the designation of wireless communication and transmission characteristics of pulse laser beam in other random media.