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Finding the laser focus

To find the laser focus:

  • Mount a red laser on the optics
  • Use the red laser and a camera find the direction and the position of the laser beam
  • Remove the red laser and mount the IR laser on the optics apparatus, with the help of the camera try to find the beam spot
  • Find the focus using the manual control of optics apparatus
  • Using the camera move the beam spot to the active zone of the sensor
  • Use te maual control of the base to identify the position of an edge of the sensor
  • Use the particulars software to do a 2D scan along the beam axis, near the focus' position, and in one direction from a zone with signal to a zone without it
  • To do a scan2D with the particulars software you need to:
    • use the stage control to move the base in the position of the start of the scan
    • press the button 'Set as Start' to set the position you moved the base as the start poin of the scan
    • in 'Movement' you can decide wich axis move (x, y, z) the number of steps of the movement (Nx, Ny, Nz) and the magnitude of each step (dx, dy, dz)
    • after inserting your desired paramerter start the scan pressing 'Start DAQ' in the 'General' tab
  • To find the position of the focus make a 2D plot of the maximum of the signal, and the find for wich value of the position on the beam axis you have the bigger diffences between two near bin on the other axis
  • An esample of the result of the scan:
    • Plot of the maximum value of the signal in y and z Plot of the maximum value of the signal in y and z
    • Plot of the difference between one bin and the previous along the y axis Plot of the difference between on bin an the previous along the y axis
    • the analisys indicates that the position of the focus is at z = 7320