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4.2 Substantial adjustment to seed alignment
15
17. Once
P
REF
is optimised, adjust the orientation of the half-wave plate
mounted in the endcap of the input isolator (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.
18. Verify optimum seed alignment by again walking the
M1, M2
mirror
pair according to step 15 (with very small adjustments).
19. 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.
20. 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 mea-
sure 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 to achieve bet-
ter mode-matching and repeat step 15. It may take a number of
iterations to maximise
P
REF
.
21. Measure PI curves before and after the
TA
output isolator and com-
pare with the curves in the system test report.
22. If the measured and factory curves still differ by more than 10%,
contact
MOGL
abs customer support.