Anisotropy of beam wander of focused beam in atmospheric boundary layer above sea level

The beam wander of focused laser beam in atmospheric boundary layer was studied experimentally over 1 000 m path at five meters above sea level using a position sensitive photomultiplier tube (PSPMT). A new experimental setup was designed to directly measure two dimensional position variations in the active area of 80 mm diameter. The high spatial resolution of the new setup reaching 1 mm is better than that of the quadrant detector and the detector array system markedly. This system is better than the ordinary imaging systems for its high sampling frequency of 80 kHz and wide dynamic range. The statistic results show that the beam wander is strongly anisotropic. The beam wander in horizontal direction is between 5.61 mm and 14.83 mm and in vertical direction always varies from 3.54 mm to