Laser beam analysis──the beam effective radius approach

A laser beam analysis method is proposed by using the beam effective radius R(z)with the measurements of beam width d(z)and beam divergence angle θ.The location of the beam z0 and the times-diffraction-limit-factor M2 can be determined with relative high accuracy. The method is usable for CW Iaser beam,repetition pulsed laser beam and single pulsed laser beam.Two practical apparatus designs are also proposed.