Real-time measurement of laser beam quality factor (M2) by imaging transverse scattered light

It is presented a new method that allows real-time measurement of the laser beam quality from a single lateral image of a beam propagating in a scattering medium. The development of this method involved studies of an adequate scattering medium and the design of an image acquisition optical system. Comparing with traditional methods, this new method is faster and less exhaustive, providing multiple beam diameters measurements with the same (or even better) accuracy from a unique image in real time. For a single mode HeNe laser beam, it was obtained the value M-2 = 1.1 +/- 0.1.