M2 parameter
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"M2 Parameter" is a measurement to compare a real laser beam to an ideal Gaussian laser beam. It can be express as.
[m^2=\frac]
Where [D_0] is the real beam diameter and [d_0] is the ideal beam diameter. Alternatively the M2 Parameter can be expressed as.
[m^2=\frac]
Where [\Omega \Theta] is the product of real beam radius at the beam waist and far field divergence and [\omega \theta] is the product of ideal beam radius at the beam waist and far field divergence. Since it is impossible to measure the ideal beam parameters, the product of ideal beam waist radius and divergence can be calculated from knowing the laser wavelength [\omega \theta=\frac]. Thus M2 can be expressed using real beam parameters as.
[\frac]
Measuring M2 Parameter of a Real Beam
The M2 Parameter of a real beam is typically measured using an imaging array to measure beam diameter various distances away from an imaging lens. From that data one can determine the beam waist radius and far field divergence. From knowing the wavelength of the laser M2 parameters can be calculated.
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