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Part 4. Optimize Astigmatism

Now that the Face Angle of the focusing optics is a function of variable x, we create a graph of the cavity mode on one of the cavity end mirrors. This will allow us to find the angle needed to compensate for the astigmatism introduced by the Brewster-angled crystal.

• 
  Select one of the end mirrors.
• Select menu Tools | Optic Graph, or click the  Optic Graph button on the toolbar.
• 
  If you do not see any lines on the graph, click near the upper limit of the Y axis and type a larger number, such as 2000. Or, edit the Y-Axis Range field in the Property Manager.

• The graph shows the sagittal (red) and tangential (blue) spot sizes on the selected mirror, as a function of the incidence angle (x) of the curved mirrors. The actual astigmatism compensation angle will depend on your cavity spacing.
• Note that besides the Slider in the Property Manager, you can also drag the grey line on the graph to change the value of the x variable.