Using Human Hair to Observe Transverse Modes:

In this part of the experiment, the laser beam was projected on to a surface so as to maximize the cross sectional area of the beam. A cardboard box with sheets of white paper taped to it was used as a "projection screen" for the beam. Transverse modes were produced by using a piece of human hair. As did the circular aperture, the strand of hair effectively created losses for certain modes. For example, if we compare the TEM10q mode and the TEM00q mode, we can see that introducing the hair into the laser cavity may block out part of the TEM00q while allowing the TEM10q mode to pass through entirely(See figure below).

The loss introduced by the hair causes the TEM00q to stop lasing, so we only see the TEM10q. The modes were "photographed" and the pictures digitized using a video camera and some computer software. These images resemble the spacial mode distribution diagrams discussed in the introduction.

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