METHOD FOR DIRECT MEASUREMENT OF THE VARIANCE OF LASER-BEAMS

A method permitting direct measurement of the spatial variance along a given transverse direction of any laser beam is described. The proced ure relies on the use of a transmission filter whose local transmissiv ity varies spatially as an inverted parabola. The variance and the fir st moment of a transverse beam intensity distribution are readily obta ined simply by measurement of the maximum power transmitted through th e filter as this filter is moved across the beam's section.