______________________________________________________________
6
Device alignment and installation
The TCF has been calibrated at the factory and mounted before shipping. In
order to use the device, users only need to align it correctly with the laser beam
and carefully regulate the temperature set point.
In order to obtain the best performance, the etalon plate needs to be aligned
orthogonally to the laser beam and the temperature precisely tuned on a
transmission maximum. It is very important that the laser beam waist is as small
as possible when passing inside the device: using the device with a beam
diameter larger than 2 mm will noticeably decrease the throughput. A low beam
divergence is also required to obtain the best transmittance, which will decrease
otherwise. We thus suggest to position the unit as close as possible to the laser
source output and/or to use an initial collimation lens between the source and
the TCF, to obtain the lowest possible power loss and reduce the need of
alignment checks. JRS can provide an extension cable for the device head, if it
should be necessary to detach it from the control box and place it in a narrow
space or in a difficult to reach position.
In order to align the TCF unit, unscrew
the alignment tool and slide it inside the
etalon hole as shown in Fig. 4: it will
provide a guide for alignment. It is
usually advisable, for safety of operation,
to dim the incoming laser beam in this
phase.
At first, place the device on the optical
table and fix the base in a temporary
position, as close as possible to the
correct one. The holes on the base allow
the device to be moved sideways as
required. The first phase of alignment consists in fixing the operating height.
Under the active head, a plastic support ring is provided to fix a reference height
on the post: at first, loosen the white fixing screw on the plastic support ring with
a screwdriver and slide it downwards so that the active head can move freely
along the post.
Slide the base on the bench horizontally and move vertically the active head (by
loosening the lateral big plastic screw, too) until the alignment tool hole is at the
same height of the incoming laser beam. After fixing temporarily the active head
in this position, move the support ring upwards against the active head bottom
and lock it into this new position: at this point, the active head will not be able to
move downwards anymore.
As a second step, move and rotate the device in order to have the beam
entering the centring tool and to see a laser light back reflection on some
distance surface. Move the device (and rotate the active head if needed) in
order to reflect the laser beam back to itself on the horizontal plane; fix it to the
optical workbench when a good approximation alignment has been reached.
The etalon can also be rotated around the horizontal axis by loosening and then
tightening again the active head fixing screw (letter D in
Fig. 2). By using all
Fig.
4
:
centering
tool
positioned for alignment.
