Two-Photon Spectroscopy
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Background
When certain materials are bombarded with very intense light they are able to able to absorb two lower power photons and enter an excited state. The electron quickly jumps back down from the higher energy level and releases energy as light in fluorescence. The sample is excited by light of one wavelength while fluorescing at a different wavelength. Typically a range of exciting wavelengths are tested and the fluorescence is measured at a specific wavelength that is characteristic for that material. The end result is a graph that shows the overall intensity of fluorescence compared to the exciting wavelength indicating that two photon absorption has occurred.
See complete wiki article Two Photon Absorption
Operation
TPA with the reference sample method
TPA with well characterized beam
This is a typical optical table setup for a two photon spectroscopic study. The particular arranged of the light path is dependent on the lab but the basic components would be the same.
<swf width= "640" height="480">http://depts.washington.edu/cmditr/media/twophotonspec.swf</swf>
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External Links ===
See also SPIE Optipedia Mode Locking