...
There is a camera installed in the beam path that views the laser as it emerges from the axicon. If the wavefront is nice and flat we will see the clean bullseye pattern below on the left. But if the incoming beam looks like a saddle or trefoil when the beam reaches the axicon, we get patterns that look like these on the right. We can solve these phase issue with a deformable mirror. Essentially the deformable mirror is made of a somewhat flexible glass and has a bunch of tiny pistons allowing us to change the shape of the mirror surface to impart a corrected phase on an aberrated wavefront .
Rail Camera
In the path of the beam, after the axicon, we have placed a camera on a movable rail. This allows us to record the intensity of the Bessel beam at several different positions. As of August 2023 we have only acquired one data set of 20 images taken at each of 10 positions. Below is an example of the analysis process. The raw image is shown on the left. Then the image is scanned for a maximum and smaller ROI is set around the located maximum, shown in the second image. After this, a two dimensional zeroth order Bessel function of the first kind squared is fit over the data as shown in the third image. The amplitude of each fit Bessel is stored and plotted at after each image is analyzed.
Downstream Holed Mirrors (Near and Far)
...