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<a accesskey="3" href="page.php?w=M_squared&amp;p=2">3.Next</a>
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<p>In <a href="page.php?w=laser_science">laser science</a>, the parameter <b>M<sup>2</sup></b>, also known as the <b>beam propagation ratio</b> or <b>beam quality factor</b> is a measure of <a href="page.php?w=laser_beam_quality">laser beam quality</a>. It represents the degree of variation of a beam from an ideal <a href="page.php?w=Gaussian_beam">Gaussian beam</a>. It is calculated from the ratio of the <a href="page.php?w=beam_parameter_product">beam parameter product</a> (BPP) of the beam to that of a Gaussian beam with the same <a href="page.php?w=wavelength">wavelength</a>.</p><p>
<a accesskey="3" href="page.php?w=M_squared&amp;p=2">3.Next</a>
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