Alpes Lasers ECLK, Руководство пользователя

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3.3 Back lens alignment
Figure 3.5: (left): Initial attachment of the front lens mounted on its adjuster. (right):
After a coarse geometrical alignment.
the focus adjuster knob.
Prepare at hand a suitable mid-infrared detector or imager.
Connect the pulser board, connect to the ECLK server and open the external cav-
ity client. Set up the pulsing scheme according to the laser specifications. Set the
drive voltage on laser to zero volts and switch on the electrical connection. Set up the
value of threshold voltage and gradually increase up to the maximum voltage value.
See Section 2.3.3 for details on how to operate the pulser board.
Place the detector in front of the back lens, move it in the xy-plane and find the signal.
As the lens is not well aligned, the beam spot lies out of the optical axis. Unscrew
little bit the adjuster screws (half thread is enough) and shift gently the lens mount.
Observe if the beam shape improves with a non-axial shift.
If you do not find any signal, the reason can be a large distance of the lens from
the laser facet. In such a case, the intensity of the signal is very small and difficult to
track with an insufficiently sensitive detector. Untighten the adjuster screw and make
sure that the lens holder is as close as possible to the laser submount.
Fine back lens alignment follows. Touch the adjuster knob to optimize the collimated
spot. You should notice a change from a divergent beam spot over a collimated one
to a divergent one again. If you, on the other hand, notice a progressive improvement
(towards one or other direction), it means that the lens is placed too far or too close
and you have to modify it.
You can notice from the beam shape and its position with respect to the optical axis if
the lens needs to be shifted in the xz-plane.
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2018 SA
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