We define a new parameter about Laguerre-Gaussian (LG) beams, named $Q^{ l}_{ p}$, which is only related to mode indices $p$ and $l$. This parameter is able to both evaluate and distinguish LG beams. The $Q^{ l}_{ p}$ values are first calculated theoretically and then measured experimentally for several different LG beams. Another mode quality parameter, $ M^{ 2} $ value, is also measured. The comparison between $Q^{ l}_{ p}$ and $ M^{ 2}$ shows same trend for the quality of LG mode, while the measurement of $Q^{ l}_{ p}$ is much easier than $ M^{ 2}$.
Categories: physics.optics