Difference between revisions of "Spatial filter"
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[[Image:Laser gaussian profile.svg|thumb|300px|A gaussian power distribution ]] | [[Image:Laser gaussian profile.svg|thumb|300px|A gaussian power distribution ]] | ||
see | see [wikipedia.org:Gaussian_beam] | ||
Revision as of 13:45, 26 May 2011
A laser beam is by definition coherent with respect to longitudinal wavelengths which is determined by the length of the cavity. But coherent light can also exhibit transverse modes. A cross section of laser beam might exhibit a combination of various modes creating an uneven intensity. The spatial filter is a device such as a pinhole used to eliminate transverse modes.
A pinhole selects for the central TEM0 mode and blocks all the others.
The result is a clean gaussian distribution of beam power across the cross section.
see [wikipedia.org:Gaussian_beam]