M² Measurement & Analysis

M², or beam quality factor, is a dimensionless parameter that characterizes the degree of imperfection of a real-world laser beam. The lower the value of M², the more tightly the beam can be focused to a small spot. A theoretical perfect TEM₀₀ beam has an M² value of 1. In reality, however, no laser beam is perfect; limitations of the laser cavity, the lasing medium, and/or the output/ancillary optics, etc., mean that real-world beams are not the diffraction-limited, Gaussian profile, pure TEM₀₀ mode described in textbooks. Complex beams contain multiple mode contributions that increase M². Even a "good" laboratory HeNe laser has an M² of around 1.05 to 1.2.

Best Products for ISO 11146 Compliant M² Measurement

DataRay offers a wide variety of beam profilers that can measure M². These include beam profiling cameras and the Beam’R2 when mounted on an M2DU translation stage, with automated M² measurements in the DataRay software.

The full-featured DataRay software also supports manual M² measurements with when any of our instruments are mounted on a third-party translation stage (with the user entering the sequential stage positions).

It's important to note that measuring M² on a translation stage requires an appropriate lens assembly for beams that are not already focused to measurable size (with enough working distance).

Additionally, relative M² measurements (with lower absolute accuracy) can be made in real-time using the BeamMap2 multiple Z plane scanning slit beam profiler. This can be a great option for quick M² optimization.

If you’re unsure which product is most suitable for your application or have the need for something custom, please contact us.