COURSE 1, INTRODUCTION TO LASERS
MODULE 9, SPATIAL CHARACTERISTICS OF LASERS
Comments from Neil Miller concerning variations/tips on completeing the
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 XY translation stagewith fiber-optic probe attachedto
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.
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 aperturewith reference to Figure 8as the main laboratory procedure
pointing out that the laboratory is easy to do and gives reliable results.