Leno Pedrottionesey

(4/4/2000)

    Comments from Neil Miller concerning variations/tips on completeing the measurement labs:

• Students in Neil's labs measure both beam diameter and beam divergence. They make a series of pin holes in aluminum sheets, measure the pinholes and use them as a series of apertures. They send the beam thru ??? aperture in turn and use an X–Y translation stage–with fiber-optic probe attached–to scan across the beam, moving the translator manually. They repeat for other apertures (pinholes). From the profile scans obtained, they determine both beam divergence and beam spot size for each pinhole and draw conclusions. What is the effect of the pinhole size?

• To further heighten interest in this laboratory, students introduce a spatial filter to "clean up" the beam. Then they scan the beam through a given aperture with both the filter and unfiltered beam. They compare beam profiles for the two cases and determine what the action of the spatial filter has been. They also make a hologram of the beam cross-section, with and without filtering, to see directly the effect of the spatial filter on the beam profile.
  

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Leno Pedrottitwosey

(4/4/2000)

Some instructors in the field prefer to carry out the laboratory associated with fiber optic beam scanning method to determine beam diameter (2w) as a demonstration. They prefer to complete the beam diameter measurement via transmission through an aperture–with reference to Figure 8–as the main laboratory procedure pointing out that the laboratory is easy to do and gives reliable results.

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