MOGlabs MOA, Manual, Page: 33 / 66

5.1 Seed alignment
23
9. Check that the seed laser power before the
TA
(position
B
in fig. 5.1)
has not changed during the adjustment procedure and corresponds
to the seed power from the system test report. If it has changed,
again adjust the seed laser current so that the power at position
B
matches a listed value in the
Guide for seed coupling at low and high
tapered amplifier current
table in the system test report. Iterate the
walking procedure from step 8 again (with very small adjustments).
10. Once
P
REF
is optimised, adjust the orientation of the half-wave plate
mounted in the input isolator endcap for
MOA
(see fig. 4.3, by first
loosening the set screw indicated. Rotate the half-wave plate to
maximise power out of the
TA
diode, then re-tighten the set screw.
For
MOA(C)
(and sometimes
MOA
,
MOA(L)
) the half-wave plate is in-
stead mounted on the chassis straight after the input aperture.
11. Verify optimum seed alignment by again walking the
M1, M2
mirror
pair according to step 8 (with very small adjustments).
12. Record the final
TA
output power,
P
REF
, along with the seed power
and injection current. Temporarily block the seed beam and record
the unseeded amplifier output power. Compare the measured
P
REF
with the value from the table
Guide for seed coupling at low and
high tapered amplifier current
, either
Before isolator
or
After isolator
column in the test report, as appropriate.
13. If
P
REF
has been measured after the output isolator and it is not
within 10% of the value given in the system test report, instead
measure and compare the
TA
power before the isolator for agreement.
If there is still more than 10% difference from the test report value,
slightly adjust the
TA
input lens focus (
z
) position and repeat step 8.
It may take a number of iterations to maximise
P
REF
.
14. Measure PI curves before and after the output isolator and compare
with the curves in the system test report.
15. If the measured and factory curves differ by more than 10%, contact
MOGL
abs customer support.