MOGlabs MOA, Manual, Page: 31 / 66

5.1 Seed alignment
21
system test report, typically 10 mW (20 mW for some
TA
diodes). If an
input isolator is installed in the
MOA
, measure between that isolator
and the
TA
diode.
5. The seed laser should be stable in power and frequency, i.e. not
near a mode-hop and not ramping the piezo. The divergence of the
beam should be similar to the divergence of the reverse propagating
TA
beam. Check the collimation of the seed laser using a shear
plate (shearing interferometer) or
M
2
beam profiler and if necessary
adjust the focus of the seed laser to achieve collimation (refer to the
CEL
manual). If a shear plate or
M
2
beam profiler is unavailable, the
spot size of the seed laser beam should be minimised at 5 m distance
from the seed laser. For fibre coupled
MOA
input, collimation can be
adjusted using the focus adjustment tool provided (see Appendix 7).
6. For the
MOA
and
MOA(L)
configuration, ensure the seed laser beam
is incident at the centre of the chassis input aperture and is both
parallel to the long edge of the chassis.
7. Adjust
M1
to reflect the seed laser beam into the input isolator aper-
ture (if installed). Ensure that the seed laser beam goes through the
centre of the input and output isolator apertures without clipping.
Measure the transmission efficiency of the Faraday isolator and (if
installed) adjust the half-waveplate installed on the input aperture
of the
MOA
chassis to optimise transmission efficiency. Otherwise,
rotate the entire isolator body in its mount to optimise transmission
if necessary. Compare the isolator efficiency with the factory effi-
ciency values from the system test report. If the value from the test
report and the measured efficiency are different by more than 10%,
contact
MOGL
abs customer support.
For the
MOA(L)
and
MOA(C)
, an isolator external to the
MOA(L)
or
MOA(C)
should be installed (preferably) immediately after the seed
laser.
8. Use
M1
and
M2
to align the seed laser beam with the
TA
reverse
propagating beam. Both beams should be collinear and overlapping
over the longest distance that is practical (if an input isolator is