Difference between revisions of "Spatial filter"
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[[Image:Spatial coherence pinhole.png|thumb|300px|Coherent wavefront also have transverse waves which are elimnated by a pinhole. ]] | [[Image:Spatial coherence pinhole.png|thumb|300px|Coherent wavefront also have transverse waves which are elimnated by a pinhole. ]] | ||
<swf width="500" height="400">Z-scanclean.swf</swf> | <swf width="500" height="400">/images/7/71/Z-scanclean.swf</swf> | ||
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The result is a clean gaussian distribution of beam power across the cross section. This is desirable for many optical setups such as the [[Femtosecond Z-Scan Spectrometer]] | The result is a clean gaussian distribution of beam power across the cross section. This is desirable for many optical setups such as the [[Femtosecond Z-Scan Spectrometer]] | ||
Revision as of 08:54, 7 June 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.
<swf width="500" height="400">/images/7/71/Z-scanclean.swf</swf>
The result is a clean gaussian distribution of beam power across the cross section. This is desirable for many optical setups such as the Femtosecond Z-Scan Spectrometer
