For this procedure, the white protective cover on the pump laser
assembly has to be removed which gives access to the pump laser
power.
Class 3B lasers are hazardous to the eye from direct beam viewing,
and from specular reflections even for short and unintentional
exposures! Therefore, it is absolutely necessary to take overall safety
measures when operating the source.
1. If not already turned off, turn off the laser.
2. W Remove the long-pass filters, which are positioned right in front of the adjustable
fiber couplers (see Figure 3).
3. Remove the screw on top of the white cover and lift it off.
4. Disconnect the single mode fibers from the electronic control unit (always use the
protective caps to cover fiber ends and optical inputs).
5. Remove the half wave plate from the pump assembly. Remove the polarizers.
6. Connect the fiber checker module to one of the single mode fibers and switch it on. You
should see red light coming out of one of the fiber couplers. You can reduce the
intensity if you retract the fiber 1 or 2 mm from the fiber checker module. Try to use as
little intensity as possible for a more precise alignment. You can reduce the intensity
even more if you retract the fiber 1 or 2 mm from the fiber checker module.
7. Turn on the pump laser as faint as possible. Just enough to see the spot on a white piece
of paper.
8. In order to align the system, you have to make the red beam hit two marks: the left
engraved alignment cross (see Figure 7) and – when inserted – the right engraving on
the alignment helper plate. Each time you insert the alignment helper plate, move it in
the slit to make sure, the blue pump laser hits the central vertical engraving. If the
pump is slightly above or below the horizontal marking, adjust the red beam for this
same height.
Note the diagonal beam path, i.e. use the left cross together with the right mark for one
beam and vice versa later for the second arm.
This alignment can only be accomplished iteratively: first, align for the engraving on the
helper plate using the two screws of the coupler mount, then remove the plate and
align for the small cross using the screws of the mirror mount. Repeat this until both
marks are hit simultaneously.
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