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3.2.2.2 Adjusting the YAG Channel Optics
WARNING! When the optics bench cover is removed, exposure to hazardous high voltages is present. 10kV is
present on the pod assembly when the lamps are starting, and may be present any time the system is turned
on. B+ is present on the terminal block whenever the system is on, and is present up to 15 minutes after the
system is turned off.
Refer to Fig. 3.4 The channel HR, OC and relay mirrors all have the same basic adjustment mechanics. The
mirror is held in a mirror mount by a metal retainer. The mount attaches to one of the optics bench walls by a
single mounting screw with spring. The spring pulls the mount towards the wall - two adjusting screws and a
ball bearing hold the mount out away from its mounting surface against the tension of the spring. One
adjusting screw provides horizontal movement and the other provides vertical movement.
A locking nut is threaded onto each adjusting screw. To unlock the screw for adjustment back the locking
screw away from the collar. Once adjustment is complete, lock down the adjustment screw by turning the nut
down against the collar. As is common in such mechanical lock down set ups, the locking down process will
change the adjustment a bit, so use the locking down to bring the optic to its optimum position. It is best to use
the hex wrench to hold the adjusting screw in place while tightening down the locking nut with the box end
wrench. The adjusting screws require a 7/64th hex head wrench. The locking nuts require a 7/16th box end
wrench.
The channel HR and OC must first be aligned to each other through the length of the YAG rod in order to
achieve lasing. Once the two mirrors are aligned to provide a usable output (will make a burn on photopaper),
the two optics are adjusted together to "walk" the YAG output so that it is centered in the first relay mirror.
Finally, the OC is adjusted to peak the power out of the cavity into the center of the first relay mirror.
The channel first and second (plano) relay mirrors are adjusted to center the channel YAG beam through the
wedge optics and into the center of the fiber port. The first relay mirror is the far (fiber port) adjustment (it is
concave, and provides less positional change to the beam downstream at the fiber port). The second relay
mirror is near (wedge optic) adjustment, it moves the beam much more than the first relay mirror. In general,
unless the beam is grossly out of center at the second wedge aperture, the second relay mirror should not be
adjusted.
There are also two turning mirrors that steer all the YAG channels off the galvo/servo mirror down towards
the fiber port. These mirrors do not normally require adjustment. Obviously, adjusting one of these mirrors
will affect all four YAG channels. The adjustment and mounting scheme is the same as that for the channel
optics.
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